Implement single-valued, non-variadic function literals and

function calling.  Implement a type compiler and named types.
Implement a universal scope containing built-in named types,
and some built-in constants.  Implement a simple virtual
machine for executing statements and single-valued return.

Fix many places that incorrectly dealt with named types.  In
particular, the Type.Zero methods now use the type's bit count
to determine the appropriate value representation.  As a
result, a bit count of 0 now means architecture-dependent and
bounded types use unsafe.Sizeof to determine the correct
bounds.  Previously, the bounds on a 32-bit machine would have
been wrong.

Eliminated Type.compatible, since the implementation is
equivalent for all types.  Added Type.rep that shallowly
strips named types.  Replaced almost all uses of Type.literal
with Type.rep.

Fix implementation of assign-op's so it only evaluates the
left side once.  As part of this, there is now a generic way
to separate out the effect and value of an expression.

R=rsc
APPROVED=rsc
DELTA=1530  (1244 added, 68 deleted, 218 changed)
OCL=32184
CL=32230

usr/austin/eval/compiler.go

+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package eval
+
+import (
+	"eval";
+	"fmt";
+	"go/ast";
+	"go/scanner";
+	"go/token";
+)
+
+
+type positioned interface {
+	Pos() token.Position;
+}
+
+
+// A compiler captures information used throughout an entire
+// compilation.  Currently it includes only the error handler.
+//
+// TODO(austin) This might actually represent package level, in which
+// case it should be package compiler.
+type compiler struct {
+	errors scanner.ErrorHandler;
+}
+
+func (a *compiler) diagAt(pos positioned, format string, args ...) {
+	a.errors.Error(pos.Pos(), fmt.Sprintf(format, args));
+}
+
+type FuncDecl struct
+func (a *compiler) compileFunc(scope *Scope, decl *FuncDecl, body *ast.BlockStmt) (func (f *Frame) Func)
+type exprCompiler struct
+func (a *compiler) compileExpr(scope *Scope, expr ast.Expr, constant bool) *exprCompiler
+func (a *compiler) compileType(scope *Scope, typ ast.Expr) Type
+func (a *compiler) compileFuncType(scope *Scope, typ *ast.FuncType) *FuncDecl
+
+func (a *compiler) compileArrayLen(scope *Scope, expr ast.Expr) (int64, bool)
+
+
+type codeBuf struct
+// A funcCompiler captures information used throughout the compilation
+// of a single function body.
+type funcCompiler struct {
+	*compiler;
+	outVars []*Variable;
+	// Whether the out variables are named.  This affects what
+	// kinds of return statements are legal.
+	outVarsNamed bool;
+	*codeBuf;
+	err bool;
+}
+
+
+// A blockCompiler captures information used throughout the compilation
+// of a single block within a function.
+type blockCompiler struct {
+	*funcCompiler;
+	scope *Scope;
+	returned bool;
+}
+
+func (a *blockCompiler) compileBlock(body *ast.BlockStmt)
+
+
+// An exprContext stores information used throughout the compilation
+// of a single expression.  It does not embed funcCompiler because
+// expressions can appear at top level.
+//
+// TODO(austin) Rename exprCompiler to exprNodeCompiler and rename
+// this to exprCompiler.
+type exprContext struct {
+	*compiler;
+	scope *Scope;
+	constant bool;
+}

usr/austin/eval/decls.go

@@ -16,12 +16,14 @@ type Value interface
 
 type Type interface {
 	// literal returns this type with all names recursively
-	// stripped.
-	// TODO(austin) Eliminate the need for this
+	// stripped.  This should only be used when determining
+	// assignment compatibility.  To strip a named type for use in
+	// a type switch, use .rep().
 	literal() Type;
-	// compatible returns true if this type is compatible with o.
-	// XXX Assignment versus comparison compatibility?
-	compatible(o Type) bool;
+	// rep returns the representative type.  If this is a named
+	// type, this is the unnamed underlying type.  Otherwise, this
+	// is an identity operation.
+	rep() Type;
 	// isBoolean returns true if this is a boolean type.
 	isBoolean() bool;
 	// isInteger returns true if this is an integer type.
@@ -112,6 +114,13 @@ type PtrValue interface {
 	Set(Value);
 }
 
+type Func interface
+type FuncValue interface {
+	Value;
+	Get() Func;
+	Set(Func);
+}
+
 /*
  * Scopes
  */
@@ -134,17 +143,21 @@ type Def interface {}
 type Scope struct {
 	outer *Scope;
 	defs map[string] Def;
+	temps map[int] *Variable;
 	numVars int;
 	varTypes []Type;
 }
 
-func NewRootScope() *Scope
 func (s *Scope) Fork() *Scope
 func (s *Scope) DefineVar(name string, t Type) *Variable
+func (s *Scope) DefineTemp(t Type) *Variable
 func (s *Scope) DefineConst(name string, t Type, v Value) *Constant
-func (s *Scope) DefineType(name string, t Type) bool
+func (s *Scope) DefineType(name string, t Type) Type
 func (s *Scope) Lookup(name string) (Def, *Scope)
 
+// The universal scope
+var universe = &Scope{defs: make(map[string] Def), temps: make(map[int] *Variable)};
+
 /*
  * Frames
  */
@@ -156,5 +169,15 @@ type Frame struct {
 }
 
 func (f *Frame) Get(s *Scope, index int) Value
+func (f *Frame) String() string
 
 func (s *Scope) NewFrame(outer *Frame) *Frame
+
+/*
+ * Functions
+ */
+
+type Func interface {
+	NewFrame() *Frame;
+	Call(*Frame);
+}

usr/austin/eval/expr.go

@@ -7,7 +7,6 @@ package eval
 import (
 	"bignum";
 	"eval";
-	"fmt";
 	"go/ast";
 	"go/scanner";
 	"go/token";
@@ -17,14 +16,6 @@ import (
 	"strings";
 )
 
-// An exprContext stores information used throughout the compilation
-// of an entire expression.
-type exprContext struct {
-	scope *Scope;
-	constant bool;
-	errors scanner.ErrorHandler;
-}
-
 // An exprCompiler compiles a single node in an expression.  It stores
 // the whole expression's context plus information specific to this node.
 // After compilation, it stores the type of the expression and its
@@ -37,16 +28,22 @@ type exprCompiler struct {
 	evalBool func(f *Frame) bool;
 	evalUint func(f *Frame) uint64;
 	evalInt func(f *Frame) int64;
+	// TODO(austin) evalIdealInt and evalIdealFloat shouldn't be
+	// functions at all.
 	evalIdealInt func() *bignum.Integer;
 	evalFloat func(f *Frame) float64;
 	evalIdealFloat func() *bignum.Rational;
 	evalString func(f *Frame) string;
 	evalArray func(f *Frame) ArrayValue;
 	evalPtr func(f *Frame) Value;
+	evalFunc func(f *Frame) Func;
 	// Evaluate to the "address of" this value; that is, the
 	// settable Value object.  nil for expressions whose address
 	// cannot be taken.
 	evalAddr func(f *Frame) Value;
+	// Execute this expression as a statement.  Only expressions
+	// that are valid expression statements should set this.
+	exec func(f *Frame);
 	// A short string describing this expression for error
 	// messages.  Only necessary if t != nil.
 	desc string;
@@ -62,8 +59,10 @@ func newExprCompiler(c *exprContext, pos token.Position) *exprCompiler {
 
 // Operator generators
 // TODO(austin) Remove these forward declarations
-func (a *exprCompiler) genIdentOp(t Type, s *Scope, index int)
+func (a *exprCompiler) genConstant(v Value)
+func (a *exprCompiler) genIdentOp(s *Scope, index int)
 func (a *exprCompiler) genIndexArray(l *exprCompiler, r *exprCompiler)
+func (a *exprCompiler) genFuncCall(call func(f *Frame) []Value)
 func (a *exprCompiler) genStarOp(v *exprCompiler)
 func (a *exprCompiler) genUnaryOpNeg(v *exprCompiler)
 func (a *exprCompiler) genUnaryOpNot(v *exprCompiler)
@@ -94,7 +93,7 @@ func (a *exprCompiler) copyVisit(x ast.Expr) *exprCompiler {
 }
 
 func (a *exprCompiler) diag(format string, args ...) {
-	a.errors.Error(a.pos, fmt.Sprintf(format, args));
+	a.diagAt(&a.pos, format, args);
 }
 
 func (a *exprCompiler) diagOpType(op token.Token, vt Type) {
@@ -173,6 +172,13 @@ func (a *exprCompiler) asPtr() (func(f *Frame) Value) {
 	return a.evalPtr;
 }
 
+func (a *exprCompiler) asFunc() (func(f *Frame) Func) {
+	if a.evalFunc == nil {
+		log.Crashf("tried to get %v node as FuncType", a.t);
+	}
+	return a.evalFunc;
+}
+
 /*
  * Common expression manipulations
  */
@@ -208,7 +214,7 @@ func (a *exprCompiler) convertTo(t Type) *exprCompiler {
 	}
 
 	// Check bounds
-	if t, ok := t.(BoundedType); ok {
+	if t, ok := t.rep().(BoundedType); ok {
 		if rat.Cmp(t.minVal()) < 0 {
 			a.diag("constant %v underflows %v", ratToString(rat), t);
 			return nil;
@@ -222,7 +228,7 @@ func (a *exprCompiler) convertTo(t Type) *exprCompiler {
 	// Convert rat to type t.
 	res := a.copy();
 	res.t = t;
-	switch t := t.(type) {
+	switch t := t.rep().(type) {
 	case *uintType:
 		n, d := rat.Value();
 		f := n.Quo(bignum.MakeInt(false, d));
@@ -260,14 +266,13 @@ func (a *exprCompiler) convertTo(t Type) *exprCompiler {
 // type, or produce an error.
 //
 // errOp specifies the operation name to use for error messages, such
-// as "assignment", or "function call".  errPos, if non-zero,
-// specifies the position of this assignment (for tuple assignments or
-// function arguments).  errPosName specifies the name to use for
-// positions.
+// as "assignment", or "function call".  errPosName specifies the name
+// to use for positions.  errPos, if non-zero, specifies the position
+// of this assignment (for tuple assignments or function arguments).
 //
 // If the assignment fails to typecheck, this generates an error
 // message and returns nil, nil.
-func mkAssign(lt Type, r *exprCompiler, errOp string, errPos int, errPosName string) (Type, func(lv Value, f *Frame)) {
+func mkAssign(lt Type, r *exprCompiler, errOp string, errPosName string, errPos int) (Type, func(lv Value, f *Frame)) {
 	// However, when [an ideal is] (used in an expression)
 	// assigned to a variable or typed constant, the destination
 	// must be able to represent the assigned value.
@@ -299,7 +304,7 @@ func mkAssign(lt Type, r *exprCompiler, errOp string, errPos int, errPosName str
 	} else {
 		// Values of any type may always be assigned to
 		// variables of compatible static type.
-		if !lt.compatible(r.t) {
+		if lt.literal() != r.t.literal() {
 			if errPos == 0 {
 				r.diag("illegal operand types for %s\n\t%v\n\t%v", errOp, lt, r.t);
 			} else {
@@ -330,28 +335,16 @@ func (a *exprCompiler) DoIdent(x *ast.Ident) {
 	switch def := def.(type) {
 	case *Constant:
 		a.t = def.Type;
-		switch _ := a.t.literal().(type) {
-		case *idealIntType:
-			val := def.Value.(IdealIntValue).Get();
-			a.evalIdealInt = func() *bignum.Integer { return val; };
-		case *idealFloatType:
-			val := def.Value.(IdealFloatValue).Get();
-			a.evalIdealFloat = func() *bignum.Rational { return val; };
-		default:
-			log.Crashf("unexpected constant type: %v", a.t);
-		}
+		a.genConstant(def.Value);
 		a.desc = "constant";
 	case *Variable:
 		if a.constant {
-			a.diag("expression must be a constant");
+			a.diag("variable %s used in constant expression", x.Value);
 			return;
 		}
 		a.t = def.Type;
 		defidx := def.Index;
-		a.genIdentOp(def.Type, dscope, defidx);
-		a.evalAddr = func(f *Frame) Value {
-			return f.Get(dscope, defidx);
-		};
+		a.genIdentOp(dscope, defidx);
 		a.desc = "variable";
 	case Type:
 		a.diag("type %v used as expression", x.Value);
@@ -423,7 +416,28 @@ func (a *exprCompiler) DoStringList(x *ast.StringList) {
 }
 
 func (a *exprCompiler) DoFuncLit(x *ast.FuncLit) {
-	log.Crash("Not implemented");
+	// TODO(austin) Closures capture their entire defining frame
+	// instead of just the variables they use.
+
+	decl := a.compileFuncType(a.scope, x.Type);
+	if decl == nil {
+		// TODO(austin) Try compiling the body, perhaps with
+		// dummy definitions for the arguments
+		return;
+	}
+
+	evalFunc := a.compileFunc(a.scope, decl, x.Body);
+	if evalFunc == nil {
+		return;
+	}
+
+	if a.constant {
+		a.diag("function literal used in constant expression");
+		return;
+	}
+
+	a.t = decl.Type;
+	a.evalFunc = evalFunc;
 }
 
 func (a *exprCompiler) DoCompositeLit(x *ast.CompositeLit) {
@@ -445,8 +459,8 @@ func (a *exprCompiler) DoIndexExpr(x *ast.IndexExpr) {
 	}
 
 	// Type check object
-	if lt, ok := l.t.literal().(*PtrType); ok {
-		if et, ok := lt.Elem.literal().(*ArrayType); ok {
+	if lt, ok := l.t.rep().(*PtrType); ok {
+		if et, ok := lt.Elem.rep().(*ArrayType); ok {
 			// Automatic dereference
 			nl := l.copy();
 			nl.t = et;
@@ -459,7 +473,7 @@ func (a *exprCompiler) DoIndexExpr(x *ast.IndexExpr) {
 	intIndex := false;
 	var maxIndex int64 = -1;
 
-	switch lt := l.t.literal().(type) {
+	switch lt := l.t.rep().(type) {
 	case *ArrayType:
 		at = lt.Elem;
 		intIndex = true;
@@ -488,7 +502,7 @@ func (a *exprCompiler) DoIndexExpr(x *ast.IndexExpr) {
 		// XXX(Spec) It's unclear if ideal floats with no
 		// fractional part are allowed here.  6g allows it.  I
 		// believe that's wrong.
-		switch _ := r.t.literal().(type) {
+		switch _ := r.t.rep().(type) {
 		case *idealIntType:
 			val := r.asIdealInt()();
 			if val.IsNeg() || (maxIndex != -1 && val.Cmp(bignum.Int(maxIndex)) >= 0) {
@@ -522,7 +536,7 @@ func (a *exprCompiler) DoIndexExpr(x *ast.IndexExpr) {
 	a.t = at;
 
 	// Compile
-	switch lt := l.t.literal().(type) {
+	switch lt := l.t.rep().(type) {
 	case *ArrayType:
 		a.t = lt.Elem;
 		// TODO(austin) Bounds check
@@ -533,8 +547,18 @@ func (a *exprCompiler) DoIndexExpr(x *ast.IndexExpr) {
 			return lf(f).Elem(rf(f));
 		};
 
+	case *stringType:
+		// TODO(austin) Bounds check
+		lf := l.asString();
+		rf := r.asInt();
+		// TODO(austin) This pulls over the whole string in a
+		// remote setting, instead of just the one character.
+		a.evalUint = func(f *Frame) uint64 {
+			return uint64(lf(f)[rf(f)]);
+		}
+
 	default:
-		log.Crashf("Compilation of index into %T not implemented", l.t.literal());
+		log.Crashf("Compilation of index into %T not implemented", l.t);
 	}
 }
 
@@ -543,7 +567,95 @@ func (a *exprCompiler) DoTypeAssertExpr(x *ast.TypeAssertExpr) {
 }
 
 func (a *exprCompiler) DoCallExpr(x *ast.CallExpr) {
-	log.Crash("Not implemented");
+	// TODO(austin) Type conversions look like calls, but will
+	// fail in DoIdent right now.
+	//
+	// TODO(austin) Magic built-in functions
+	//
+	// TODO(austin) Variadic functions.
+
+	// Compile children
+	bad := false;
+	l := a.copyVisit(x.Fun);
+	if l.t == nil {
+		bad = true;
+	}
+	as := make([]*exprCompiler, len(x.Args));
+	ats := make([]Type, len(as));
+	for i := 0; i < len(x.Args); i++ {
+		as[i] = a.copyVisit(x.Args[i]);
+		if as[i].t == nil {
+			bad = true;
+		}
+		ats[i] = as[i].t;
+	}
+	if bad {
+		return;
+	}
+
+	// Type check
+	if a.constant {
+		a.diag("function call in constant context");
+		return;
+	}
+
+	// XXX(Spec) Calling a named function type is okay.  I really
+	// think there needs to be a general discussion of named
+	// types.  A named type creates a new, distinct type, but the
+	// type of that type is still whatever it's defined to.  Thus,
+	// in "type Foo int", Foo is still an integer type and in
+	// "type Foo func()", Foo is a function type.
+	lt, ok := l.t.rep().(*FuncType);
+	if !ok {
+		a.diag("cannot call non-function type %v", l.t);
+		return;
+	}
+
+	if len(as) != len(lt.In) {
+		msg := "too many";
+		if len(as) < len(lt.In) {
+			msg = "not enough";
+		}
+		a.diag("%s arguments to call\n\t%s\n\t%s", msg, typeListString(lt.In, nil), typeListString(ats, nil));
+		return;
+	}
+
+	// The arguments must be single-valued expressions assignment
+	// compatible with the parameters of F.
+	afs := make([]func(lv Value, f *Frame), len(as));
+	for i := 0; i < len(as); i++ {
+		var at Type;
+		at, afs[i] = mkAssign(lt.In[i], as[i], "function call", "argument", i + 1);
+		if at == nil {
+			bad = true;
+		}
+	}
+	if bad {
+		return;
+	}
+
+	nResults := len(lt.Out);
+	if nResults != 1 {
+		log.Crashf("Multi-valued return type not implemented");
+	}
+	a.t = lt.Out[0];
+
+	// Compile
+	lf := l.asFunc();
+	call := func(f *Frame) []Value {
+		fun := lf(f);
+		fr := fun.NewFrame();
+		for i, af := range afs {
+			af(fr.Vars[i], f);
+		}
+		fun.Call(fr);
+		return fr.Vars[len(afs):len(afs)+nResults];
+	};
+	a.genFuncCall(call);
+
+	// Function calls, method calls, and channel operations can
+	// appear in statement context.
+	a.exec = func(f *Frame) { call(f) };
 }
 
 func (a *exprCompiler) DoStarExpr(x *ast.StarExpr) {
@@ -552,21 +664,22 @@ func (a *exprCompiler) DoStarExpr(x *ast.StarExpr) {
 		return;
 	}
 
-	switch vt := v.t.literal().(type) {
+	switch vt := v.t.rep().(type) {
 	case *PtrType:
-		// TODO(austin) If this is vt.Elem() I get a
-		// "call of a non-function: Type" error
 		a.t = vt.Elem;
 		a.genStarOp(v);
-		vf := v.asPtr();
-		a.evalAddr = func(f *Frame) Value { return vf(f) };
-		a.desc = "* expression";
+		a.desc = "indirect expression";
 
 	default:
 		a.diagOpType(token.MUL, v.t);
 	}
 }
 
+func (a *exprCompiler) genUnaryAddrOf(v *exprCompiler) {
+	vf := v.evalAddr;
+	a.evalPtr = func(f *Frame) Value { return vf(f) };
+}
+
 var unaryOpDescs = make(map[token.Token] string)
 
 func (a *exprCompiler) DoUnaryExpr(x *ast.UnaryExpr) {
@@ -589,7 +702,6 @@ func (a *exprCompiler) DoUnaryExpr(x *ast.UnaryExpr) {
 			a.diagOpType(x.Op, v.t);
 			return;
 		}
-		// TODO(austin) Unnamed bool?  Named bool?
 		a.t = BoolType;
 
 	case token.XOR:
@@ -645,8 +757,7 @@ func (a *exprCompiler) DoUnaryExpr(x *ast.UnaryExpr) {
 		a.genUnaryOpXor(v);
 
 	case token.AND:
-		vf := v.evalAddr;
-		a.evalPtr = func(f *Frame) Value { return vf(f) };
+		a.genUnaryAddrOf(v);
 
 	default:
 		log.Crashf("Compilation of unary op %v not implemented", x.Op);
@@ -702,11 +813,12 @@ func (a *exprCompiler) doBinaryExpr(op token.Token, l, r *exprCompiler) {
 		}
 	}
 
+	// XXX(Spec) "The operand types in binary operations must be
+	// compatible" should say the types must be *identical*.
+
 	// Useful type predicates
-	// TODO(austin) The spec is wrong here.  The types must be
-	// identical, not compatible.
-	compat := func() bool {
-		return l.t.compatible(r.t);
+	same := func() bool {
+		return l.t == r.t;
 	};
 	integers := func() bool {
 		return l.t.isInteger() && r.t.isInteger();
@@ -719,28 +831,27 @@ func (a *exprCompiler) doBinaryExpr(op token.Token, l, r *exprCompiler) {
 		return l.t == StringType && r.t == StringType;
 	};
 	booleans := func() bool {
-		// TODO(austin) Deal with named types
-		return l.t == BoolType && r.t == BoolType;
+		return l.t.isBoolean() && r.t.isBoolean();
 	};
 
 	// Type check
 	switch op {
 	case token.ADD:
-		if !compat() || (!integers() && !floats() && !strings()) {
+		if !same() || (!integers() && !floats() && !strings()) {
 			a.diagOpTypes(op, origlt, origrt);
 			return;
 		}
 		a.t = l.t;
 
 	case token.SUB, token.MUL, token.QUO:
-		if !compat() || (!integers() && !floats()) {
+		if !same() || (!integers() && !floats()) {
 			a.diagOpTypes(op, origlt, origrt);
 			return;
 		}
 		a.t = l.t;
 
 	case token.REM, token.AND, token.OR, token.XOR, token.AND_NOT:
-		if !compat() || !integers() {
+		if !same() || !integers() {
 			a.diagOpTypes(op, origlt, origrt);
 			return;
 		}
@@ -783,7 +894,7 @@ func (a *exprCompiler) doBinaryExpr(op token.Token, l, r *exprCompiler) {
 					log.Crashf("conversion to uintType succeeded, but conversion to idealIntType failed");
 				}
 			}
-		} else if _, ok := r.t.literal().(*uintType); !ok {
+		} else if _, ok := r.t.rep().(*uintType); !ok {
 			a.diag("right operand of shift must be unsigned");
 			return;
 		}
@@ -793,6 +904,7 @@ func (a *exprCompiler) doBinaryExpr(op token.Token, l, r *exprCompiler) {
 			// non-ideal"?  Russ says the ideal should be
 			// converted to an int.  6g propagates the
 			// type down from assignments as a hint.
+
 			l = l.convertTo(IntType);
 			if l == nil {
 				return;
@@ -816,7 +928,6 @@ func (a *exprCompiler) doBinaryExpr(op token.Token, l, r *exprCompiler) {
 		// the type of the left operand, and NOT an unnamed
 		// boolean type.
 
-		// TODO(austin) Named bool type
 		a.t = BoolType;
 
 	case token.ARROW:
@@ -829,7 +940,8 @@ func (a *exprCompiler) doBinaryExpr(op token.Token, l, r *exprCompiler) {
 	case token.LSS, token.GTR, token.LEQ, token.GEQ:
 		// ... booleans may be compared only for equality or
 		// inequality.
-		if l.t.literal() == BoolType || r.t.literal() == BoolType {
+
+		if l.t.isBoolean() || r.t.isBoolean() {
 			a.diagOpTypes(op, origlt, origrt);
 			return;
 		}
@@ -855,7 +967,6 @@ func (a *exprCompiler) doBinaryExpr(op token.Token, l, r *exprCompiler) {
 		// actually explained in the Comparison compatibility
 		// section.
 		log.Crashf("Binary op %v not implemented", op);
-		// TODO(austin) Unnamed bool?  Named bool?
 		a.t = BoolType;
 
 	default:
@@ -976,8 +1087,37 @@ func (a *exprCompiler) DoChanType(x *ast.ChanType) {
 	log.Crash("Not implemented");
 }
 
-func compileExpr(expr ast.Expr, scope *Scope, errors scanner.ErrorHandler) *exprCompiler {
-	ec := newExprCompiler(&exprContext{scope, false, errors}, expr.Pos());
+// TODO(austin) This is a hack to eliminate a circular dependency
+// between type.go and expr.go
+func (a *compiler) compileArrayLen(scope *Scope, expr ast.Expr) (int64, bool) {
+	lenExpr := a.compileExpr(scope, expr, true);
+	if lenExpr == nil {
+		return 0, false;
+	}
+	if !lenExpr.t.isInteger() {
+		a.diagAt(expr, "array size must be an integer");
+		return 0, false;
+	}
+
+	if lenExpr.t.isIdeal() {
+		lenExpr = lenExpr.convertTo(IntType);
+		if lenExpr == nil {
+			return 0, false;
+		}
+	}
+
+	switch _ := lenExpr.t.rep().(type) {
+	case *intType:
+		return lenExpr.evalInt(nil), true;
+	case *uintType:
+		return int64(lenExpr.evalUint(nil)), true;
+	}
+	log.Crashf("unexpected integer type %T", lenExpr.t);
+	return 0, false;
+}
+
+func (a *compiler) compileExpr(scope *Scope, expr ast.Expr, constant bool) *exprCompiler {
+	ec := newExprCompiler(&exprContext{a, scope, constant}, expr.Pos());
 	expr.Visit(ec);
 	if ec.t == nil {
 		return nil;
@@ -985,8 +1125,55 @@ func compileExpr(expr ast.Expr, scope *Scope, errors scanner.ErrorHandler) *expr
 	return ec;
 }
 
+// extractEffect separates out any effects that the expression may
+// have, returning a function that will perform those effects and a
+// new exprCompiler that is guaranteed to be side-effect free.  These
+// are the moral equivalents of "temp := &expr" and "*temp".
+//
+// Implementation limit: The expression must be addressable.
+func (a *exprCompiler) extractEffect() (func(f *Frame), *exprCompiler) {
+	if a.evalAddr == nil {
+		// This is a much easier case, but the code is
+		// completely different.
+		log.Crash("extractEffect only implemented for addressable expressions");
+	}
+
+	// Create temporary
+	tempScope := a.scope;
+	tempType := NewPtrType(a.t);
+	// TODO(austin) These temporaries accumulate in the scope.
+	temp := tempScope.DefineTemp(tempType);
+	tempIdx := temp.Index;
+
+	// Generate "temp := &e"
+	addr := a.copy();
+	addr.t = tempType;
+	addr.genUnaryAddrOf(a);
+
+	_, assign := mkAssign(tempType, addr, "", "", 0);
+	if assign == nil {
+		log.Crashf("extractEffect: mkAssign type check failed");
+	}
+
+	effect := func(f *Frame) {
+		tempVal := f.Get(tempScope, tempIdx);
+		assign(tempVal, f);
+	};
+
+	// Generate "*temp"
+	getTemp := a.copy();
+	getTemp.t = tempType;
+	getTemp.genIdentOp(tempScope, tempIdx);
+
+	deref := a.copy();
+	deref.t = a.t;
+	deref.genStarOp(getTemp);
+
+	return effect, deref;
+}
+
 /*
- * Public interface
+ * Testing interface
  */
 
 type Expr struct {
@@ -1000,14 +1187,15 @@ func (expr *Expr) Eval(f *Frame) Value {
 	return v;
 }
 
-func CompileExpr(expr ast.Expr, scope *Scope) (*Expr, os.Error) {
+func CompileExpr(scope *Scope, expr ast.Expr) (*Expr, os.Error) {
 	errors := scanner.NewErrorVector();
+	cc := &compiler{errors};
 
-	ec := compileExpr(expr, scope, errors);
+	ec := cc.compileExpr(scope, expr, false);
 	if ec == nil {
 		return nil, errors.GetError(scanner.Sorted);
 	}
-	switch t := ec.t.(type) {
+	switch t := ec.t.rep().(type) {
 	case *boolType:
 		return &Expr{t, func(f *Frame, out Value) { out.(BoolValue).Set(ec.evalBool(f)) }}, nil;
 	case *uintType:
@@ -1024,6 +1212,8 @@ func CompileExpr(expr ast.Expr, scope *Scope) (*Expr, os.Error) {
 		return &Expr{t, func(f *Frame, out Value) { out.(StringValue).Set(ec.evalString(f)) }}, nil;
 	case *PtrType:
 		return &Expr{t, func(f *Frame, out Value) { out.(PtrValue).Set(ec.evalPtr(f)) }}, nil;
+	case *FuncType:
+		return &Expr{t, func(f *Frame, out Value) { out.(FuncValue).Set(ec.evalFunc(f)) }}, nil;
 	}
 	log.Crashf("unexpected type %v", ec.t);
 	panic();
@@ -1034,8 +1224,46 @@ func CompileExpr(expr ast.Expr, scope *Scope) (*Expr, os.Error) {
  * Everything below here is MACHINE GENERATED by gen.py genOps
  */
 
-func (a *exprCompiler) genIdentOp(t Type, s *Scope, index int) {
-	switch _ := t.literal().(type) {
+func (a *exprCompiler) genConstant(v Value) {
+	switch _ := a.t.rep().(type) {
+	case *boolType:
+		val := v.(BoolValue).Get();
+		a.evalBool = func(f *Frame) bool { return val };
+	case *uintType:
+		val := v.(UintValue).Get();
+		a.evalUint = func(f *Frame) uint64 { return val };
+	case *intType:
+		val := v.(IntValue).Get();
+		a.evalInt = func(f *Frame) int64 { return val };
+	case *idealIntType:
+		val := v.(IdealIntValue).Get();
+		a.evalIdealInt = func() *bignum.Integer { return val };
+	case *floatType:
+		val := v.(FloatValue).Get();
+		a.evalFloat = func(f *Frame) float64 { return val };
+	case *idealFloatType:
+		val := v.(IdealFloatValue).Get();
+		a.evalIdealFloat = func() *bignum.Rational { return val };
+	case *stringType:
+		val := v.(StringValue).Get();
+		a.evalString = func(f *Frame) string { return val };
+	case *ArrayType:
+		val := v.(ArrayValue).Get();
+		a.evalArray = func(f *Frame) ArrayValue { return val };
+	case *PtrType:
+		val := v.(PtrValue).Get();
+		a.evalPtr = func(f *Frame) Value { return val };
+	case *FuncType:
+		val := v.(FuncValue).Get();
+		a.evalFunc = func(f *Frame) Func { return val };
+	default:
+		log.Crashf("unexpected constant type %v at %v", a.t, a.pos);
+	}
+}
+
+func (a *exprCompiler) genIdentOp(s *Scope, index int) {
+	a.evalAddr = func(f *Frame) Value { return f.Get(s, index) };
+	switch _ := a.t.rep().(type) {
 	case *boolType:
 		a.evalBool = func(f *Frame) bool { return f.Get(s, index).(BoolValue).Get() };
 	case *uintType:
@@ -1050,15 +1278,17 @@ func (a *exprCompiler) genIdentOp(t Type, s *Scope, index int) {
 		a.evalArray = func(f *Frame) ArrayValue { return f.Get(s, index).(ArrayValue).Get() };
 	case *PtrType:
 		a.evalPtr = func(f *Frame) Value { return f.Get(s, index).(PtrValue).Get() };
+	case *FuncType:
+		a.evalFunc = func(f *Frame) Func { return f.Get(s, index).(FuncValue).Get() };
 	default:
-		log.Crashf("unexpected identifier type %v at %v", t.literal(), a.pos);
+		log.Crashf("unexpected identifier type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genIndexArray(l *exprCompiler, r *exprCompiler) {
 	lf := l.asArray();
 	rf := r.asInt();
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *boolType:
 		a.evalBool = func(f *Frame) bool { return lf(f).Elem(rf(f)).(BoolValue).Get() };
 	case *uintType:
@@ -1073,14 +1303,40 @@ func (a *exprCompiler) genIndexArray(l *exprCompiler, r *exprCompiler) {
 		a.evalArray = func(f *Frame) ArrayValue { return lf(f).Elem(rf(f)).(ArrayValue).Get() };
 	case *PtrType:
 		a.evalPtr = func(f *Frame) Value { return lf(f).Elem(rf(f)).(PtrValue).Get() };
+	case *FuncType:
+		a.evalFunc = func(f *Frame) Func { return lf(f).Elem(rf(f)).(FuncValue).Get() };
 	default:
-		log.Crashf("unexpected result type %v at %v", l.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
+	}
+}
+
+func (a *exprCompiler) genFuncCall(call func(f *Frame) []Value) {
+	switch _ := a.t.rep().(type) {
+	case *boolType:
+		a.evalBool = func(f *Frame) bool { return call(f)[0].(BoolValue).Get() };
+	case *uintType:
+		a.evalUint = func(f *Frame) uint64 { return call(f)[0].(UintValue).Get() };
+	case *intType:
+		a.evalInt = func(f *Frame) int64 { return call(f)[0].(IntValue).Get() };
+	case *floatType:
+		a.evalFloat = func(f *Frame) float64 { return call(f)[0].(FloatValue).Get() };
+	case *stringType:
+		a.evalString = func(f *Frame) string { return call(f)[0].(StringValue).Get() };
+	case *ArrayType:
+		a.evalArray = func(f *Frame) ArrayValue { return call(f)[0].(ArrayValue).Get() };
+	case *PtrType:
+		a.evalPtr = func(f *Frame) Value { return call(f)[0].(PtrValue).Get() };
+	case *FuncType:
+		a.evalFunc = func(f *Frame) Func { return call(f)[0].(FuncValue).Get() };
+	default:
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genStarOp(v *exprCompiler) {
 	vf := v.asPtr();
-	switch _ := a.t.literal().(type) {
+	a.evalAddr = func(f *Frame) Value { return vf(f) };
+	switch _ := a.t.rep().(type) {
 	case *boolType:
 		a.evalBool = func(f *Frame) bool { return vf(f).(BoolValue).Get() };
 	case *uintType:
@@ -1095,13 +1351,15 @@ func (a *exprCompiler) genStarOp(v *exprCompiler) {
 		a.evalArray = func(f *Frame) ArrayValue { return vf(f).(ArrayValue).Get() };
 	case *PtrType:
 		a.evalPtr = func(f *Frame) Value { return vf(f).(PtrValue).Get() };
+	case *FuncType:
+		a.evalFunc = func(f *Frame) Func { return vf(f).(FuncValue).Get() };
 	default:
-		log.Crashf("unexpected result type %v at %v", v.t.literal().(*PtrType).Elem.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genUnaryOpNeg(v *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *uintType:
 		vf := v.asUint();
 		a.evalUint = func(f *Frame) uint64 { return -vf(f) };
@@ -1120,22 +1378,22 @@ func (a *exprCompiler) genUnaryOpNeg(v *exprCompiler) {
 		val := vf().Neg();
 		a.evalIdealFloat = func() *bignum.Rational { return val };
 	default:
-		log.Crashf("unexpected result type %v at %v", v.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genUnaryOpNot(v *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *boolType:
 		vf := v.asBool();
 		a.evalBool = func(f *Frame) bool { return !vf(f) };
 	default:
-		log.Crashf("unexpected result type %v at %v", v.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genUnaryOpXor(v *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *uintType:
 		vf := v.asUint();
 		a.evalUint = func(f *Frame) uint64 { return ^vf(f) };
@@ -1147,12 +1405,12 @@ func (a *exprCompiler) genUnaryOpXor(v *exprCompiler) {
 		val := vf().Neg().Sub(bignum.Int(1));
 		a.evalIdealInt = func() *bignum.Integer { return val };
 	default:
-		log.Crashf("unexpected result type %v at %v", v.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genBinOpAdd(l *exprCompiler, r *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *uintType:
 		lf := l.asUint();
 		rf := r.asUint();
@@ -1180,12 +1438,12 @@ func (a *exprCompiler) genBinOpAdd(l *exprCompiler, r *exprCompiler) {
 		rf := r.asString();
 		a.evalString = func(f *Frame) string { return lf(f) + rf(f) };
 	default:
-		log.Crashf("unexpected result type %v at %v", l.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genBinOpSub(l *exprCompiler, r *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *uintType:
 		lf := l.asUint();
 		rf := r.asUint();
@@ -1209,12 +1467,12 @@ func (a *exprCompiler) genBinOpSub(l *exprCompiler, r *exprCompiler) {
 		val := lf().Sub(rf());
 		a.evalIdealFloat = func() *bignum.Rational { return val };
 	default:
-		log.Crashf("unexpected result type %v at %v", l.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genBinOpMul(l *exprCompiler, r *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *uintType:
 		lf := l.asUint();
 		rf := r.asUint();
@@ -1238,12 +1496,12 @@ func (a *exprCompiler) genBinOpMul(l *exprCompiler, r *exprCompiler) {
 		val := lf().Mul(rf());
 		a.evalIdealFloat = func() *bignum.Rational { return val };
 	default:
-		log.Crashf("unexpected result type %v at %v", l.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genBinOpQuo(l *exprCompiler, r *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *uintType:
 		lf := l.asUint();
 		rf := r.asUint();
@@ -1267,12 +1525,12 @@ func (a *exprCompiler) genBinOpQuo(l *exprCompiler, r *exprCompiler) {
 		val := lf().Quo(rf());
 		a.evalIdealFloat = func() *bignum.Rational { return val };
 	default:
-		log.Crashf("unexpected result type %v at %v", l.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genBinOpRem(l *exprCompiler, r *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *uintType:
 		lf := l.asUint();
 		rf := r.asUint();
@@ -1287,12 +1545,12 @@ func (a *exprCompiler) genBinOpRem(l *exprCompiler, r *exprCompiler) {
 		val := lf().Rem(rf());
 		a.evalIdealInt = func() *bignum.Integer { return val };
 	default:
-		log.Crashf("unexpected result type %v at %v", l.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genBinOpAnd(l *exprCompiler, r *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *uintType:
 		lf := l.asUint();
 		rf := r.asUint();
@@ -1307,12 +1565,12 @@ func (a *exprCompiler) genBinOpAnd(l *exprCompiler, r *exprCompiler) {
 		val := lf().And(rf());
 		a.evalIdealInt = func() *bignum.Integer { return val };
 	default:
-		log.Crashf("unexpected result type %v at %v", l.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genBinOpOr(l *exprCompiler, r *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *uintType:
 		lf := l.asUint();
 		rf := r.asUint();
@@ -1327,12 +1585,12 @@ func (a *exprCompiler) genBinOpOr(l *exprCompiler, r *exprCompiler) {
 		val := lf().Or(rf());
 		a.evalIdealInt = func() *bignum.Integer { return val };
 	default:
-		log.Crashf("unexpected result type %v at %v", l.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genBinOpXor(l *exprCompiler, r *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *uintType:
 		lf := l.asUint();
 		rf := r.asUint();
@@ -1347,12 +1605,12 @@ func (a *exprCompiler) genBinOpXor(l *exprCompiler, r *exprCompiler) {
 		val := lf().Xor(rf());
 		a.evalIdealInt = func() *bignum.Integer { return val };
 	default:
-		log.Crashf("unexpected result type %v at %v", l.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genBinOpAndNot(l *exprCompiler, r *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *uintType:
 		lf := l.asUint();
 		rf := r.asUint();
@@ -1367,12 +1625,12 @@ func (a *exprCompiler) genBinOpAndNot(l *exprCompiler, r *exprCompiler) {
 		val := lf().AndNot(rf());
 		a.evalIdealInt = func() *bignum.Integer { return val };
 	default:
-		log.Crashf("unexpected result type %v at %v", l.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genBinOpShl(l *exprCompiler, r *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *uintType:
 		lf := l.asUint();
 		rf := r.asUint();
@@ -1382,12 +1640,12 @@ func (a *exprCompiler) genBinOpShl(l *exprCompiler, r *exprCompiler) {
 		rf := r.asUint();
 		a.evalInt = func(f *Frame) int64 { return lf(f) << rf(f) };
 	default:
-		log.Crashf("unexpected result type %v at %v", l.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func (a *exprCompiler) genBinOpShr(l *exprCompiler, r *exprCompiler) {
-	switch _ := a.t.literal().(type) {
+	switch _ := a.t.rep().(type) {
 	case *uintType:
 		lf := l.asUint();
 		rf := r.asUint();
@@ -1397,12 +1655,12 @@ func (a *exprCompiler) genBinOpShr(l *exprCompiler, r *exprCompiler) {
 		rf := r.asUint();
 		a.evalInt = func(f *Frame) int64 { return lf(f) >> rf(f) };
 	default:
-		log.Crashf("unexpected result type %v at %v", l.t.literal(), a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
 	}
 }
 
 func genAssign(lt Type, r *exprCompiler) (func(lv Value, f *Frame)) {
-	switch _ := lt.literal().(type) {
+	switch _ := lt.rep().(type) {
 	case *boolType:
 		rf := r.asBool();
 		return func(lv Value, f *Frame) { lv.(BoolValue).Set(rf(f)) };
@@ -1424,8 +1682,11 @@ func genAssign(lt Type, r *exprCompiler) (func(lv Value, f *Frame)) {
 	case *PtrType:
 		rf := r.asPtr();
 		return func(lv Value, f *Frame) { lv.(PtrValue).Set(rf(f)) };
+	case *FuncType:
+		rf := r.asFunc();
+		return func(lv Value, f *Frame) { lv.(FuncValue).Set(rf(f)) };
 	default:
-		log.Crashf("unexpected left operand type %v at %v", lt.literal(), r.pos);
+		log.Crashf("unexpected left operand type %v at %v", lt, r.pos);
 	}
 	panic();
 }

usr/austin/eval/func.go

+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package eval
+
+import (
+	"container/vector";
+	"eval";
+)
+
+/*
+ * Virtual machine
+ */
+
+type vm struct {
+	pc uint;
+	// The current execution frame.  If execution is within a
+	// block, this may be a child of the original function
+	// activation frame.
+	f *Frame;
+	// The original function activation frame.  This is used to
+	// access function out args.
+	activation *Frame;
+}
+
+type code []func(*vm)
+
+func (i code) exec(fr *Frame) {
+	v := vm{0, fr, fr};
+
+	l := uint(len(i));
+	for v.pc < l {
+		pc := v.pc;
+		v.pc++;
+		i[pc](&v);
+	}
+}
+
+/*
+ * Code buffer
+ */
+
+type codeBuf struct {
+	instrs code;
+}
+
+func newCodeBuf() *codeBuf {
+	return &codeBuf{make(code, 0, 16)};
+}
+
+func (b codeBuf) push(instr func(*vm)) {
+	n := len(b.instrs);
+	if n >= cap(b.instrs) {
+		a := make(code, n, n*2);
+		for i := range b.instrs {
+			a[i] = b.instrs[i];
+		}
+		b.instrs = a;
+	}
+	b.instrs = b.instrs[0:n+1];
+	b.instrs[n] = instr;
+}
+
+func (b codeBuf) get() code {
+	// Freeze this buffer into an array of exactly the right size
+	a := make(code, len(b.instrs));
+	for i := range b.instrs {
+		a[i] = b.instrs[i];
+	}
+	return code(a);
+}
+
+/*
+ * User-defined functions
+ */
+
+type evalFunc struct {
+	sc *Scope;
+	fr *Frame;
+	code code;
+}
+
+func (f *evalFunc) NewFrame() *Frame {
+	return f.sc.NewFrame(f.fr);
+}
+
+func (f *evalFunc) Call(fr *Frame) {
+	f.code.exec(fr);
+}

usr/austin/eval/scope.go

@@ -6,14 +6,15 @@ package eval
 
 import (
 	"eval";
+	"fmt";
 )
 
-func NewRootScope() *Scope {
-	return &Scope{defs: make(map[string] Def)};
-}
-
 func (s *Scope) Fork() *Scope {
-	return &Scope{outer: s, defs: make(map[string] Def)};
+	return &Scope{
+		outer: s,
+		defs: make(map[string] Def),
+		temps: make(map[int] *Variable)
+	};
 }
 
 func (s *Scope) DefineVar(name string, t Type) *Variable {
@@ -21,8 +22,15 @@ func (s *Scope) DefineVar(name string, t Type) *Variable {
 		return nil;
 	}
 	v := &Variable{s.numVars, t};
-	s.numVars++;
 	s.defs[name] = v;
+	s.numVars++;
+	return v;
+}
+
+func (s *Scope) DefineTemp(t Type) *Variable {
+	v := &Variable{s.numVars, t};
+	s.temps[s.numVars] = v;
+	s.numVars++;
 	return v;
 }
 
@@ -35,12 +43,15 @@ func (s *Scope) DefineConst(name string, t Type, v Value) *Constant {
 	return c;
 }
 
-func (s *Scope) DefineType(name string, t Type) bool {
+func (s *Scope) DefineType(name string, t Type) Type {
 	if _, ok := s.defs[name]; ok {
-		return false;
+		return nil;
 	}
-	s.defs[name] = t;
-	return true;
+	// We take the representative type of t because multiple
+	// levels of naming are useless.
+	nt := &NamedType{s, name, t.rep()};
+	s.defs[name] = nt;
+	return nt;
 }
 
 func (s *Scope) Lookup(name string) (Def, *Scope) {
@@ -60,13 +71,23 @@ func (s *Scope) NewFrame(outer *Frame) *Frame {
 		ts := make([]Type, s.numVars);
 		for _, d := range s.defs {
 			if v, ok := d.(*Variable); ok {
-				ts[v.Index] = v.Type;
+				// Record the representative type to
+				// avoid indirecting through named
+				// types every time we drop a frame.
+				ts[v.Index] = v.Type.rep();
+			}
 		}
+		for _, v := range s.temps {
+			ts[v.Index] = v.Type.rep();
 		}
 		s.varTypes = ts;
 	}
 
 	// Create frame
+	//
+	// TODO(austin) This is probably rather expensive.  All values
+	// require heap allocation and the Zero method typically
+	// requires some computation.
 	vars := make([]Value, s.numVars);
 	for i, t := range s.varTypes {
 		vars[i] = t.Zero();
@@ -80,3 +101,36 @@ func (f *Frame) Get(s *Scope, index int) Value {
 	}
 	return f.Vars[index];
 }
+
+func stringFrame(f *Frame) (string, string) {
+	res := "";
+	indent := "";
+	if f.Outer != nil {
+		res, indent = stringFrame(f.Outer);
+	}
+
+	names := make([]string, f.Scope.numVars);
+	types := make([]Type, f.Scope.numVars);
+	for name, def := range f.Scope.defs {
+		def, ok := def.(*Variable);
+		if !ok {
+			continue;
+		}
+		names[def.Index] = name;
+		types[def.Index] = def.Type;
+	}
+	for _, def := range f.Scope.temps {
+		names[def.Index] = "(temp)";
+		types[def.Index] = def.Type;
+	}
+
+	for i, val := range f.Vars {
+		res += fmt.Sprintf("%s%-10s %-10s %s\n", indent, names[i], types[i], val);
+	}
+	return res, indent + "  ";
+}
+
+func (f *Frame) String() string {
+	res, _ := stringFrame(f);
+	return res;
+}

usr/austin/eval/stmt.go

@@ -6,27 +6,31 @@ package eval
 
 import (
 	"eval";
-	"fmt";
 	"log";
 	"os";
 	"go/ast";
 	"go/scanner";
 	"go/token";
+	"strconv";
 )
 
+/*
+ * Statement compiler
+ */
+
 type stmtCompiler struct {
-	scope *Scope;
-	errors scanner.ErrorHandler;
+	*blockCompiler;
 	pos token.Position;
-	f func (f *Frame);
-}
-
-func (a *stmtCompiler) diagAt(pos token.Position, format string, args ...) {
-	a.errors.Error(pos, fmt.Sprintf(format, args));
+	// err should be initialized to true before visiting and set
+	// to false when the statement is compiled successfully.  The
+	// function invoking Visit should or this with
+	// blockCompiler.err.  This is less error prone than setting
+	// blockCompiler.err on every failure path.
+	err bool;
 }
 
 func (a *stmtCompiler) diag(format string, args ...) {
-	a.diagAt(a.pos, format, args);
+	a.diagAt(&a.pos, format, args);
 }
 
 /*
@@ -42,7 +46,7 @@ func (a *stmtCompiler) DoDeclStmt(s *ast.DeclStmt) {
 }
 
 func (a *stmtCompiler) DoEmptyStmt(s *ast.EmptyStmt) {
-	log.Crash("Not implemented");
+	a.err = false;
 }
 
 func (a *stmtCompiler) DoLabeledStmt(s *ast.LabeledStmt) {
@@ -50,7 +54,22 @@ func (a *stmtCompiler) DoLabeledStmt(s *ast.LabeledStmt) {
 }
 
 func (a *stmtCompiler) DoExprStmt(s *ast.ExprStmt) {
-	log.Crash("Not implemented");
+	// TODO(austin) Permit any 0 or more valued function call
+	e := a.compileExpr(a.scope, s.X, false);
+	if e == nil {
+		return;
+	}
+
+	if e.exec == nil {
+		a.diag("%s cannot be used as expression statement", e.desc);
+		return;
+	}
+
+	exec := e.exec;
+	a.push(func(v *vm) {
+		exec(v.f);
+	});
+	a.err = false;
 }
 
 func (a *stmtCompiler) DoIncDecStmt(s *ast.IncDecStmt) {
@@ -58,10 +77,6 @@ func (a *stmtCompiler) DoIncDecStmt(s *ast.IncDecStmt) {
 }
 
 func (a *stmtCompiler) doAssign(s *ast.AssignStmt) {
-	if len(s.Lhs) != len(s.Rhs) {
-		log.Crashf("Unbalanced assignment not implemented %v %v %v", len(s.Lhs), s.Tok, len(s.Rhs));
-	}
-
 	bad := false;
 
 	// Compile right side first so we have the types when
@@ -69,10 +84,16 @@ func (a *stmtCompiler) doAssign(s *ast.AssignStmt) {
 	// made on the left side.
 	rs := make([]*exprCompiler, len(s.Rhs));
 	for i, re := range s.Rhs {
-		rs[i] = compileExpr(re, a.scope, a.errors);
+		rs[i] = a.compileExpr(a.scope, re, false);
 		if rs[i] == nil {
 			bad = true;
+			continue;
+		}
 	}
+
+	// Check the assignment count
+	if len(s.Lhs) != len(s.Rhs) {
+		log.Crashf("Unbalanced assignment not implemented %v %v %v", len(s.Lhs), s.Tok, len(s.Rhs));
 	}
 
 	// Compile left side and generate assigners
@@ -89,8 +110,10 @@ func (a *stmtCompiler) doAssign(s *ast.AssignStmt) {
 			// Check that it's an identifier
 			ident, ok := le.(*ast.Ident);
 			if !ok {
-				a.diagAt(le.Pos(), "left side of := must be a name");
+				a.diagAt(le, "left side of := must be a name");
 				bad = true;
+				// Suppress new defitions errors
+				nDefs++;
 				continue;
 			}
 
@@ -98,6 +121,7 @@ func (a *stmtCompiler) doAssign(s *ast.AssignStmt) {
 			if _, ok := a.scope.defs[ident.Value]; ok {
 				goto assignment;
 			}
+			nDefs++;
 
 			if rs[i] == nil {
 				// TODO(austin) Define a placeholder.
@@ -106,7 +130,7 @@ func (a *stmtCompiler) doAssign(s *ast.AssignStmt) {
 
 			// Generate assigner and get type
 			var lt Type;
-			lt, as[i] = mkAssign(nil, rs[i], "assignment", errPos, "position");
+			lt, as[i] = mkAssign(nil, rs[i], "assignment", "position", errPos);
 			if lt == nil {
 				bad = true;
 				continue;
@@ -114,14 +138,13 @@ func (a *stmtCompiler) doAssign(s *ast.AssignStmt) {
 
 			// Define identifier
 			v := a.scope.DefineVar(ident.Value, lt);
-			nDefs++;
 			if v == nil {
 				log.Crashf("Failed to define %s", ident.Value);
 			}
 		}
 
 	assignment:
-		ls[i] = compileExpr(le, a.scope, a.errors);
+		ls[i] = a.compileExpr(a.scope, le, false);
 		if ls[i] == nil {
 			bad = true;
 			continue;
@@ -136,7 +159,7 @@ func (a *stmtCompiler) doAssign(s *ast.AssignStmt) {
 		// Generate assigner
 		if as[i] == nil {
 			var lt Type;
-			lt, as[i] = mkAssign(ls[i].t, rs[i], "assignment", errPos, "position");
+			lt, as[i] = mkAssign(ls[i].t, rs[i], "assignment", "position", errPos);
 			if lt == nil {
 				bad = true;
 				continue;
@@ -144,11 +167,6 @@ func (a *stmtCompiler) doAssign(s *ast.AssignStmt) {
 		}
 	}
 
-	if bad {
-		return;
-	}
-
-
 	// A short variable declaration may redeclare variables
 	// provided they were originally declared in the same block
 	// with the same type, and at least one of the variables is
@@ -158,26 +176,31 @@ func (a *stmtCompiler) doAssign(s *ast.AssignStmt) {
 		return;
 	}
 
+	if bad {
+		return;
+	}
+
 	n := len(s.Lhs);
 	if n == 1 {
 		lf := ls[0].evalAddr;
 		assign := as[0];
-		a.f = func(f *Frame) { assign(lf(f), f) };
+		a.push(func(v *vm) { assign(lf(v.f), v.f) });
 	} else {
-		a.f = func(f *Frame) {
+		a.push(func(v *vm) {
 			temps := make([]Value, n);
 			// Assign to temporaries
 			for i := 0; i < n; i++ {
 				// TODO(austin) Don't capture ls
 				temps[i] = ls[i].t.Zero();
-				as[i](temps[i], f);
+				as[i](temps[i], v.f);
 			}
 			// Copy to destination
 			for i := 0; i < n; i++ {
-				ls[i].evalAddr(f).Assign(temps[i]);
-			}
+				ls[i].evalAddr(v.f).Assign(temps[i]);
 			}
+		});
 	}
+	a.err = false;
 }
 
 var assignOpToOp = map[token.Token] token.Token {
@@ -201,8 +224,8 @@ func (a *stmtCompiler) doAssignOp(s *ast.AssignStmt) {
 		return;
 	}
 
-	l := compileExpr(s.Lhs[0], a.scope, a.errors);
-	r := compileExpr(s.Rhs[0], a.scope, a.errors);
+	l := a.compileExpr(a.scope, s.Lhs[0], false);
+	r := a.compileExpr(a.scope, s.Rhs[0], false);
 	if l == nil || r == nil {
 		return;
 	}
@@ -212,19 +235,26 @@ func (a *stmtCompiler) doAssignOp(s *ast.AssignStmt) {
 		return;
 	}
 
-	ec := r.copy();
-	ec.pos = s.TokPos;
-	ec.doBinaryExpr(assignOpToOp[s.Tok], l, r);
-	if ec.t == nil {
+	effect, l := l.extractEffect();
+
+	binop := r.copy();
+	binop.pos = s.TokPos;
+	binop.doBinaryExpr(assignOpToOp[s.Tok], l, r);
+	if binop.t == nil {
 		return;
 	}
 
-	lf := l.evalAddr;
-	_, assign := mkAssign(l.t, r, "assignment", 0, "");
+	_, assign := mkAssign(l.t, binop, "assignment", "", 0);
 	if assign == nil {
 		return;
 	}
-	a.f = func(f *Frame) { assign(lf(f), f) };
+
+	lf := l.evalAddr;
+	a.push(func(v *vm) {
+		effect(v.f);
+		assign(lf(v.f), v.f);
+	});
+	a.err = false;
 }
 
 func (a *stmtCompiler) DoAssignStmt(s *ast.AssignStmt) {
@@ -246,7 +276,65 @@ func (a *stmtCompiler) DoDeferStmt(s *ast.DeferStmt) {
 }
 
 func (a *stmtCompiler) DoReturnStmt(s *ast.ReturnStmt) {
-	log.Crash("Not implemented");
+	// Supress return errors even if we fail to compile this
+	// return statement.
+	a.returned = true;
+
+	if len(s.Results) == 0 && (len(a.outVars) == 0 || a.outVarsNamed) {
+		// Simple case.  Simply exit from the function.
+		a.push(func(v *vm) { v.pc = ^uint(0) });
+		a.err = false;
+		return;
+	}
+
+	// TODO(austin) Might be a call of a multi-valued function.
+	// It might be possible to combine this code with the
+	// assignment code.
+	if len(s.Results) != len(a.outVars) {
+		a.diag("Unbalanced return not implemented");
+		return;
+	}
+
+	// Compile expressions and create assigners
+	bad := false;
+	rs := make([]*exprCompiler, len(s.Results));
+	as := make([]func(lv Value, f *Frame), len(s.Results));
+	for i, re := range s.Results {
+		rs[i] = a.compileExpr(a.scope, re, false);
+		if rs[i] == nil {
+			bad = true;
+			continue;
+		}
+
+		errPos := i + 1;
+		if len(s.Results) == 1 {
+			errPos = 0;
+		}
+		var lt Type;
+		lt, as[i] = mkAssign(a.outVars[i].Type, rs[i], "return", "value", errPos);
+		if as[i] == nil {
+			bad = true;
+		}
+	}
+
+	if bad {
+		return;
+	}
+
+	// Save indexes of return values
+	idxs := make([]int, len(s.Results));
+	for i, outVar := range a.outVars {
+		idxs[i] = outVar.Index;
+	}
+
+	// Compile
+	a.push(func(v *vm) {
+		for i, assign := range as {
+			assign(v.activation.Vars[idxs[i]], v.f);
+		}
+		v.pc = ^uint(0);
+	});
+	a.err = false;
 }
 
 func (a *stmtCompiler) DoBranchStmt(s *ast.BranchStmt) {
@@ -254,7 +342,19 @@ func (a *stmtCompiler) DoBranchStmt(s *ast.BranchStmt) {
 }
 
 func (a *stmtCompiler) DoBlockStmt(s *ast.BlockStmt) {
-	log.Crash("Not implemented");
+	blockScope := a.scope.Fork();
+	bc := &blockCompiler{a.funcCompiler, blockScope, false};
+
+	a.push(func(v *vm) {
+		v.f = blockScope.NewFrame(v.f);
+	});
+	bc.compileBlock(s);
+	a.push(func(v *vm) {
+		v.f = v.f.Outer;
+	});
+
+	a.returned = a.returned || bc.returned;
+	a.err = false;
 }
 
 func (a *stmtCompiler) DoIfStmt(s *ast.IfStmt) {
@@ -293,8 +393,62 @@ func (a *stmtCompiler) DoRangeStmt(s *ast.RangeStmt) {
 	log.Crash("Not implemented");
 }
 
+func (a *blockCompiler) compileBlock(block *ast.BlockStmt) {
+	for i, sub := range block.List {
+		sc := &stmtCompiler{a, sub.Pos(), true};
+		sub.Visit(sc);
+		a.err = a.err || sc.err;
+	}
+}
+
+func (a *compiler) compileFunc(scope *Scope, decl *FuncDecl, body *ast.BlockStmt) (func (f *Frame) Func) {
+	// Create body scope
+	//
+	// The scope of a parameter or result is the body of the
+	// corresponding function.
+	bodyScope := scope.Fork();
+	for i, t := range decl.Type.In {
+		bodyScope.DefineVar(decl.InNames[i].Value, t);
+	}
+	outVars := make([]*Variable, len(decl.Type.Out));
+	for i, t := range decl.Type.Out {
+		if decl.OutNames[i] != nil {
+			outVars[i] = bodyScope.DefineVar(decl.OutNames[i].Value, t);
+		} else {
+			// TODO(austin) It would be nice to have a
+			// better way to define unnamed slots.
+			outVars[i] = bodyScope.DefineVar(":out" + strconv.Itoa(i), t);
+		}
+	}
+
+	// Create block context
+	fc := &funcCompiler{a, outVars, false, newCodeBuf(), false};
+	if len(decl.OutNames) > 0 && decl.OutNames[0] != nil {
+		fc.outVarsNamed = true;
+	}
+	bc := &blockCompiler{fc, bodyScope, false};
+
+	// Compile body
+	bc.compileBlock(body);
+	if fc.err {
+		return nil;
+	}
+
+	// TODO(austin) Check that all gotos were linked?
+
+	// Check that the body returned if necessary
+	if len(decl.Type.Out) > 0 && !bc.returned {
+		// XXX(Spec) Not specified.
+		a.diagAt(&body.Rbrace, "function ends without a return statement");
+		return nil;
+	}
+
+	code := fc.get();
+	return func(f *Frame) Func { return &evalFunc{bodyScope, f, code} };
+}
+
 /*
- * Public interface
+ * Testing interface
  */
 
 type Stmt struct {
@@ -305,12 +459,17 @@ func (s *Stmt) Exec(f *Frame) {
 	s.f(f);
 }
 
-func CompileStmt(stmt ast.Stmt, scope *Scope) (*Stmt, os.Error) {
+func CompileStmt(scope *Scope, stmt ast.Stmt) (*Stmt, os.Error) {
 	errors := scanner.NewErrorVector();
-	sc := &stmtCompiler{scope, errors, stmt.Pos(), nil};
+	cc := &compiler{errors};
+	fc := &funcCompiler{cc, nil, false, newCodeBuf(), false};
+	bc := &blockCompiler{fc, scope, false};
+	sc := &stmtCompiler{bc, stmt.Pos(), true};
 	stmt.Visit(sc);
-	if sc.f == nil {
+	fc.err = fc.err || sc.err;
+	if fc.err {
 		return nil, errors.GetError(scanner.Sorted);
 	}
-	return &Stmt{sc.f}, nil;
+	code := fc.get();
+	return &Stmt{func(f *Frame) { code.exec(f); }}, nil;
 }

usr/austin/eval/type.go

@@ -7,7 +7,10 @@ package eval
 import (
 	"bignum";
 	"eval";
+	"go/ast";
 	"log";
+	"reflect";
+	"unsafe";			// For Sizeof
 )
 
 
@@ -27,6 +30,68 @@ import (
 // compared to other values of compatible static type."  That should
 // be *identical* type.
 
+/*
+ * Type array maps.  These are used to memoize composite types.
+ */
+
+type typeArrayMapEntry struct {
+	key []Type;
+	v interface {};
+	next *typeArrayMapEntry;
+}
+
+type typeArrayMap map[uintptr] *typeArrayMapEntry
+
+func hashTypeArray(key []Type) uintptr {
+	hash := uintptr(0);
+	for _, t := range key {
+		addr := reflect.NewValue(t).Addr();
+		hash = hash * 33;
+		hash ^= addr;
+	}
+	return hash;
+}
+
+func newTypeArrayMap() typeArrayMap {
+	return make(map[uintptr] *typeArrayMapEntry);
+}
+
+func (m typeArrayMap) Get(key []Type) (interface{}) {
+	ent, ok := m[hashTypeArray(key)];
+	if !ok {
+		return nil;
+	}
+
+nextEnt:
+	for ; ent != nil; ent = ent.next {
+		if len(key) != len(ent.key) {
+			continue;
+		}
+		for i := 0; i < len(key); i++ {
+			if key[i] != ent.key[i] {
+				continue nextEnt;
+			}
+		}
+		// Found it
+		return ent.v;
+	}
+
+	return nil;
+}
+
+func (m typeArrayMap) Put(key []Type, v interface{}) interface{} {
+	hash := hashTypeArray(key);
+	ent, _ := m[hash];
+
+	new := &typeArrayMapEntry{key, v, ent};
+	m[hash] = new;
+	return v;
+}
+
+/*
+ * Common type
+ */
+
 type commonType struct {
 }
 
@@ -46,18 +111,22 @@ func (commonType) isIdeal() bool {
 	return false;
 }
 
+/*
+ * Bool
+ */
+
 type boolType struct {
 	commonType;
 }
 
-var BoolType Type = &boolType{};
+var BoolType = universe.DefineType("bool", &boolType{});
 
 func (t *boolType) literal() Type {
 	return t;
 }
 
-func (t *boolType) compatible(o Type) bool {
-	return Type(t) == o;
+func (t *boolType) rep() Type {
+	return t;
 }
 
 func (t *boolType) isBoolean() bool {
@@ -65,14 +134,22 @@ func (t *boolType) isBoolean() bool {
 }
 
 func (boolType) String() string {
-	return "bool";
+	// Use angle brackets as a convention for printing the
+	// underlying, unnamed type.  This should only show up in
+	// debug output.
+	return "<bool>";
 }
 
 func (t *boolType) Zero() Value
 
+/*
+ * Uint
+ */
+
 type uintType struct {
 	commonType;
 
+	// 0 for architecture-dependent types
 	Bits uint;
 	// true for uintptr, false for all others
 	Ptr bool;
@@ -80,26 +157,31 @@ type uintType struct {
 	name string;
 }
 
-// TODO(austin) These are all technically *named types*, which matters
-// for some things.  Perhaps these should be the underlying unnamed
-// types and the named types should be created when they are put in
-// the universal scope.
 var (
-	Uint8Type   Type = &uintType{commonType{}, 8,  false, "uint8"};
-	Uint16Type  Type = &uintType{commonType{}, 16, false, "uint16"};
-	Uint32Type  Type = &uintType{commonType{}, 32, false, "uint32"};
-	Uint64Type  Type = &uintType{commonType{}, 64, false, "uint64"};
+	Uint8Type   = universe.DefineType("uint8",   &uintType{commonType{}, 8,  false, "uint8"});
+	Uint16Type  = universe.DefineType("uint16",  &uintType{commonType{}, 16, false, "uint16"});
+	Uint32Type  = universe.DefineType("uint32",  &uintType{commonType{}, 32, false, "uint32"});
+	Uint64Type  = universe.DefineType("uint64",  &uintType{commonType{}, 64, false, "uint64"});
 
-	UintType    Type = &uintType{commonType{}, 64, false, "uint"};
-	UintptrType Type = &uintType{commonType{}, 64, true,  "uintptr"};
+	UintType    = universe.DefineType("uint",    &uintType{commonType{}, 0,  false, "uint"});
+	UintptrType = universe.DefineType("uintptr", &uintType{commonType{}, 0,  true,  "uintptr"});
 )
 
+func init() {
+	// To avoid portability issues all numeric types are distinct
+	// except byte, which is an alias for uint8.
+
+	// Make byte an alias for the named type uint8.  Type aliases
+	// are otherwise impossible in Go, so just hack it here.
+	universe.defs["byte"] = universe.defs["uint8"];
+}
+
 func (t *uintType) literal() Type {
 	return t;
 }
 
-func (t *uintType) compatible(o Type) bool {
-	return Type(t) == o;
+func (t *uintType) rep() Type {
+	return t;
 }
 
 func (t *uintType) isInteger() bool {
@@ -107,7 +189,7 @@ func (t *uintType) isInteger() bool {
 }
 
 func (t *uintType) String() string {
-	return t.name;
+	return "<" + t.name + ">";
 }
 
 func (t *uintType) Zero() Value
@@ -117,9 +199,21 @@ func (t *uintType) minVal() *bignum.Rational {
 }
 
 func (t *uintType) maxVal() *bignum.Rational {
-	return bignum.MakeRat(bignum.Int(1).Shl(t.Bits).Add(bignum.Int(-1)), bignum.Nat(1));
+	bits := t.Bits;
+	if bits == 0 {
+		if t.Ptr {
+			bits = uint(8 * unsafe.Sizeof(uintptr(0)));
+		} else {
+			bits = uint(8 * unsafe.Sizeof(uint(0)));
+		}
+	}
+	return bignum.MakeRat(bignum.Int(1).Shl(bits).Add(bignum.Int(-1)), bignum.Nat(1));
 }
 
+/*
+ * Int
+ */
+
 type intType struct {
 	commonType;
 
@@ -128,26 +222,27 @@ type intType struct {
 	// depends on the architecture."  Should that be
 	// architecture-dependent?
 
+	// 0 for architecture-dependent types
 	Bits uint;
 
 	name string;
 }
 
 var (
-	Int8Type  Type = &intType{commonType{}, 8,  "int8"};
-	Int16Type Type = &intType{commonType{}, 16, "int16"};
-	Int32Type Type = &intType{commonType{}, 32, "int32"};
-	Int64Type Type = &intType{commonType{}, 64, "int64"};
+	Int8Type  = universe.DefineType("int8",  &intType{commonType{}, 8,  "int8"});
+	Int16Type = universe.DefineType("int16", &intType{commonType{}, 16, "int16"});
+	Int32Type = universe.DefineType("int32", &intType{commonType{}, 32, "int32"});
+	Int64Type = universe.DefineType("int64", &intType{commonType{}, 64, "int64"});
 
-	IntType   Type = &intType{commonType{}, 64, "int"};
+	IntType   = universe.DefineType("int",   &intType{commonType{}, 0,  "int"});
 )
 
 func (t *intType) literal() Type {
 	return t;
 }
 
-func (t *intType) compatible(o Type) bool {
-	return Type(t) == o;
+func (t *intType) rep() Type {
+	return t;
 }
 
 func (t *intType) isInteger() bool {
@@ -155,19 +250,31 @@ func (t *intType) isInteger() bool {
 }
 
 func (t *intType) String() string {
-	return t.name;
+	return "<" + t.name + ">";
 }
 
 func (t *intType) Zero() Value
 
 func (t *intType) minVal() *bignum.Rational {
-	return bignum.MakeRat(bignum.Int(-1).Shl(t.Bits - 1), bignum.Nat(1));
+	bits := t.Bits;
+	if bits == 0 {
+		bits = uint(8 * unsafe.Sizeof(int(0)));
+	}
+	return bignum.MakeRat(bignum.Int(-1).Shl(bits - 1), bignum.Nat(1));
 }
 
 func (t *intType) maxVal() *bignum.Rational {
-	return bignum.MakeRat(bignum.Int(1).Shl(t.Bits - 1).Add(bignum.Int(-1)), bignum.Nat(1));
+	bits := t.Bits;
+	if bits == 0 {
+		bits = uint(8 * unsafe.Sizeof(int(0)));
+	}
+	return bignum.MakeRat(bignum.Int(1).Shl(bits - 1).Add(bignum.Int(-1)), bignum.Nat(1));
 }
 
+/*
+ * Ideal int
+ */
+
 type idealIntType struct {
 	commonType;
 }
@@ -178,8 +285,8 @@ func (t *idealIntType) literal() Type {
 	return t;
 }
 
-func (t *idealIntType) compatible(o Type) bool {
-	return Type(t) == o;
+func (t *idealIntType) rep() Type {
+	return t;
 }
 
 func (t *idealIntType) isInteger() bool {
@@ -196,23 +303,31 @@ func (t *idealIntType) String() string {
 
 func (t *idealIntType) Zero() Value
 
+/*
+ * Float
+ */
+
 type floatType struct {
 	commonType;
+
+	// 0 for architecture-dependent type
 	Bits uint;
+
+	name string;
 }
 
 var (
-	Float32Type Type = &floatType{commonType{}, 32};
-	Float64Type Type = &floatType{commonType{}, 64};
-	FloatType   Type = &floatType{commonType{}, 64};
+	Float32Type = universe.DefineType("float32", &floatType{commonType{}, 32, "float32"});
+	Float64Type = universe.DefineType("float64", &floatType{commonType{}, 64, "float64"});
+	FloatType   = universe.DefineType("float",   &floatType{commonType{}, 0,  "float"});
 )
 
 func (t *floatType) literal() Type {
 	return t;
 }
 
-func (t *floatType) compatible(o Type) bool {
-	return Type(t) == o;
+func (t *floatType) rep() Type {
+	return t;
 }
 
 func (t *floatType) isFloat() bool {
@@ -220,7 +335,7 @@ func (t *floatType) isFloat() bool {
 }
 
 func (t *floatType) String() string {
-	return "float";
+	return "<" + t.name + ">";
 }
 
 func (t *floatType) Zero() Value
@@ -231,27 +346,39 @@ var minFloat32Val = maxFloat32Val.Neg();
 var minFloat64Val = maxFloat64Val.Neg();
 
 func (t *floatType) minVal() *bignum.Rational {
-	switch t.Bits {
+	bits := t.Bits;
+	if bits == 0 {
+		bits = uint(8 * unsafe.Sizeof(float(0)));
+	}
+	switch bits {
 	case 32:
 		return minFloat32Val;
 	case 64:
 		return minFloat64Val;
 	}
-	log.Crashf("unexpected number of floating point bits: %d", t.Bits);
+	log.Crashf("unexpected floating point bit count: %d", bits);
 	panic();
 }
 
 func (t *floatType) maxVal() *bignum.Rational {
-	switch t.Bits {
+	bits := t.Bits;
+	if bits == 0 {
+		bits = uint(8 * unsafe.Sizeof(float(0)));
+	}
+	switch bits {
 	case 32:
 		return maxFloat32Val;
 	case 64:
 		return maxFloat64Val;
 	}
-	log.Crashf("unexpected number of floating point bits: %d", t.Bits);
+	log.Crashf("unexpected floating point bit count: %d", bits);
 	panic();
 }
 
+/*
+ * Ideal float
+ */
+
 type idealFloatType struct {
 	commonType;
 }
@@ -262,8 +389,8 @@ func (t *idealFloatType) literal() Type {
 	return t;
 }
 
-func (t *idealFloatType) compatible(o Type) bool {
-	return Type(t) == o;
+func (t *idealFloatType) rep() Type {
+	return t;
 }
 
 func (t *idealFloatType) isFloat() bool {
@@ -280,36 +407,49 @@ func (t *idealFloatType) String() string {
 
 func (t *idealFloatType) Zero() Value
 
+/*
+ * String
+ */
+
 type stringType struct {
 	commonType;
 }
 
-var StringType Type = &stringType{};
+var StringType = universe.DefineType("string", &stringType{});
 
 func (t *stringType) literal() Type {
 	return t;
 }
 
-func (t *stringType) compatible(o Type) bool {
-	return Type(t) == o;
+func (t *stringType) rep() Type {
+	return t;
 }
 
 func (t *stringType) String() string {
-	return "string";
+	return "<string>";
 }
 
 func (t *stringType) Zero() Value
 
+/*
+ * Array
+ */
+
 type ArrayType struct {
 	commonType;
+
 	Len int64;
 	Elem Type;
+
 	lit Type;
 }
 
 var arrayTypes = make(map[int64] map[Type] *ArrayType);
 
 func NewArrayType(len int64, elem Type) *ArrayType {
+	// Two array types are identical if they have identical
+	// element types and the same array length.
+
 	ts, ok := arrayTypes[len];
 	if !ok {
 		ts = make(map[Type] *ArrayType);
@@ -330,8 +470,8 @@ func (t *ArrayType) literal() Type {
 	return t.lit;
 }
 
-func (t *ArrayType) compatible(o Type) bool {
-	return t.literal() == o.literal();
+func (t *ArrayType) rep() Type {
+	return t;
 }
 
 func (t *ArrayType) String() string {
@@ -341,15 +481,8 @@ func (t *ArrayType) String() string {
 func (t *ArrayType) Zero() Value
 
 /*
-func (t *ArrayType) literal() Type {
-	// TODO(austin)
-}
-
-type StructType struct {
-	commonType;
-	Names map[string] Name;
-}
-*/
+ * Pointer
+ */
 
 type PtrType struct {
 	commonType;
@@ -360,6 +493,9 @@ type PtrType struct {
 var ptrTypes = make(map[Type] *PtrType)
 
 func NewPtrType(elem Type) *PtrType {
+	// Two pointer types are identical if they have identical base
+	// types.
+
 	t, ok := ptrTypes[elem];
 	if !ok {
 		t = &PtrType{commonType{}, elem, nil};
@@ -375,8 +511,8 @@ func (t *PtrType) literal() Type {
 	return t.lit;
 }
 
-func (t *PtrType) compatible(o Type) bool {
-	return t.literal() == o.literal();
+func (t *PtrType) rep() Type {
+	return t;
 }
 
 func (t *PtrType) String() string {
@@ -386,15 +522,130 @@ func (t *PtrType) String() string {
 func (t *PtrType) Zero() Value
 
 /*
+ * Function
+ */
+
 type FuncType struct {
 	commonType;
-	// TODO(austin)
+	// TODO(austin) Separate receiver Type for methods?
+	In []Type;
+	Variadic bool;
+	Out []Type;
+	lit Type;
+}
+
+var funcTypes = newTypeArrayMap();
+var variadicFuncTypes = newTypeArrayMap();
+
+func NewFuncType(in []Type, variadic bool, out []Type) *FuncType {
+	// Two function types are identical if they have the same
+	// number of parameters and result values and if corresponding
+	// parameter and result types are identical. All "..."
+	// parameters have identical type. Parameter and result names
+	// are not required to match.
+
+	inMap := funcTypes;
+	if variadic {
+		inMap = variadicFuncTypes;
+	}
+
+	outMapI := inMap.Get(in);
+	if outMapI == nil {
+		outMapI = inMap.Put(in, newTypeArrayMap());
+	}
+	outMap := outMapI.(typeArrayMap);
+
+	tI := outMap.Get(out);
+	if tI != nil {
+		return tI.(*FuncType);
+	}
+
+	t := &FuncType{commonType{}, in, variadic, out, nil};
+	outMap.Put(out, t);
+	return t;
 }
 
 func (t *FuncType) literal() Type {
-	// TODO(austin)
+	if t.lit == nil {
+		in := make([]Type, len(t.In));
+		for i := 0; i < len(in); i++ {
+			in[i] = t.In[i].literal();
+		}
+
+		out := make([]Type, len(t.Out));
+		for i := 0; i < len(out); i++ {
+			out[i] = t.Out[i].literal();
+		}
+
+		t.lit = NewFuncType(in, t.Variadic, out);
+	}
+	return t.lit;
+}
+
+func (t *FuncType) rep() Type {
+	return t;
+}
+
+func typeListString(ts []Type, ns []*ast.Ident) string {
+	s := "";
+	for i, t := range ts {
+		if i > 0 {
+			s += ", ";
+		}
+		if ns != nil && ns[i] != nil {
+			s += ns[i].Value + " ";
+		}
+		s += t.String();
+	}
+	return s;
 }
 
+func (t *FuncType) String() string {
+	args := typeListString(t.In, nil);
+	if t.Variadic {
+		if len(args) > 0 {
+			args += ", ";
+		}
+		args += "...";
+	}
+	s := "func(" + args + ")";
+	if len(t.Out) > 0 {
+		s += " (" + typeListString(t.Out, nil) + ")";
+	}
+	return s;
+}
+
+func (t *FuncType) Zero() Value
+
+type FuncDecl struct {
+	Type *FuncType;
+	Name *ast.Ident;		// nil for function literals
+	// InNames will be one longer than Type.In if this function is
+	// variadic.
+	InNames []*ast.Ident;
+	OutNames []*ast.Ident;
+}
+
+func (t *FuncDecl) String() string {
+	args := typeListString(t.Type.In, t.InNames);
+	if t.Type.Variadic {
+		if len(args) > 0 {
+			args += ", ";
+		}
+		args += "...";
+	}
+	s := "func";
+	if t.Name != nil {
+		s += " " + t.Name.Value;
+	}
+	s += "(" + args + ")";
+	if len(t.Type.Out) > 0 {
+		s += " (" + typeListString(t.Type.Out, t.OutNames) + ")";
+	}
+	return s;
+}
+
+/*
 type InterfaceType struct {
 	// TODO(austin)
 }
@@ -410,6 +661,11 @@ type MapType struct {
 type ChanType struct {
 	// TODO(austin)
 }
+*/
+
+/*
+ * Named types
+ */
 
 type NamedType struct {
 	// Declaration scope
@@ -418,15 +674,37 @@ type NamedType struct {
 	// Underlying type
 	def Type;
 	// TODO(austin) Methods can be on NamedType or *NamedType
-	methods map[string] XXX;
+	//methods map[string] XXX;
 }
 
 func (t *NamedType) literal() Type {
 	return t.def.literal();
 }
 
+func (t *NamedType) rep() Type {
+	return t.def.rep();
+}
+
+func (t *NamedType) isBoolean() bool {
+	return t.def.isBoolean();
+}
+
 func (t *NamedType) isInteger() bool {
-	return t.isInteger();
+	return t.def.isInteger();
 }
 
-*/
+func (t *NamedType) isFloat() bool {
+	return t.def.isFloat();
+}
+
+func (t *NamedType) isIdeal() bool {
+	return false;
+}
+
+func (t *NamedType) String() string {
+	return t.name;
+}
+
+func (t *NamedType) Zero() Value {
+	return t.def.Zero();
+}

usr/austin/eval/typec.go

+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package eval
+
+import (
+	"eval";
+	"go/ast";
+	"log";
+)
+
+
+/*
+ * Type compiler
+ */
+
+// TODO(austin) Without this, I get a "conflicting definitions for
+// eval.compiler" when gopack'ing typec.6 from gobuild.
+// Interestingly, if I create the Makefile with this line, then
+// comment it out and use the Makefile, things work.
+type exprCompiler struct
+
+type typeCompiler struct {
+	*compiler;
+	scope *Scope;
+}
+
+func (a *typeCompiler) compileType(x ast.Expr) Type
+
+func (a *typeCompiler) compileIdent(x *ast.Ident) Type {
+	def, dscope := a.scope.Lookup(x.Value);
+	if def == nil {
+		a.diagAt(x, "%s: undefined", x.Value);
+		return nil;
+	}
+	switch def := def.(type) {
+	case *Constant:
+		a.diagAt(x, "constant %v used as type", x.Value);
+		return nil;
+	case *Variable:
+		a.diagAt(x, "variable %v used as type", x.Value);
+		return nil;
+	case Type:
+		return def;
+	}
+	log.Crashf("name %s has unknown type %T", x.Value, def);
+	return nil;
+}
+
+func (a *typeCompiler) compileArrayType(x *ast.ArrayType) *ArrayType {
+	// Compile length expression
+	if x.Len == nil {
+		a.diagAt(x, "slice types not implemented");
+		return nil;
+	}
+	if _, ok := x.Len.(*ast.Ellipsis); ok {
+		a.diagAt(x.Len, "... array initailizers not implemented");
+		return nil;
+	}
+	l, ok := a.compileArrayLen(a.scope, x.Len);
+
+	// Compile element type
+	elem := a.compileType(x.Elt);
+
+	if !ok {
+		return nil;
+	}
+	if l < 0 {
+		a.diagAt(x.Len, "array length must be non-negative");
+		return nil;
+	}
+	if elem == nil {
+		return nil;
+	}
+
+	return NewArrayType(l, elem);
+}
+
+func (a *typeCompiler) compilePtrType(x *ast.StarExpr) *PtrType {
+	elem := a.compileType(x.X);
+	if elem == nil {
+		return nil;
+	}
+	return NewPtrType(elem);
+}
+
+func countFields(fs []*ast.Field) int {
+	n := 0;
+	for _, f := range fs {
+		if f.Names == nil {
+			n++;
+		} else {
+			n += len(f.Names);
+		}
+	}
+	return n;
+}
+
+func (a *typeCompiler) compileFields(fs []*ast.Field) ([]Type, []*ast.Ident) {
+	n := countFields(fs);
+	ts := make([]Type, n);
+	ns := make([]*ast.Ident, n);
+
+	bad := false;
+	i := 0;
+	for fi, f := range fs {
+		t := a.compileType(f.Type);
+		if t == nil {
+			bad = true;
+		}
+		if f.Names == nil {
+			// TODO(austin) In a struct, this has an
+			// implicit name.  However, this also triggers
+			// for function return values, which should
+			// not be given names.
+			ns[i] = nil;
+			ts[i] = t;
+			i++;
+			continue;
+		}
+		for _, n := range f.Names {
+			ns[i] = n;
+			ts[i] = t;
+			i++;
+		}
+	}
+
+	if bad {
+		return nil, nil;
+	}
+	return ts, ns;
+}
+
+func (a *typeCompiler) compileFuncType(x *ast.FuncType) *FuncDecl {
+	// TODO(austin) Variadic function types
+
+	bad := false;
+
+	in, inNames := a.compileFields(x.Params);
+	out, outNames := a.compileFields(x.Results);
+
+	if in == nil || out == nil {
+		return nil;
+	}
+	return &FuncDecl{NewFuncType(in, false, out), nil, inNames, outNames};
+}
+
+func (a *typeCompiler) compileType(x ast.Expr) Type {
+	switch x := x.(type) {
+	case *ast.Ident:
+		return a.compileIdent(x);
+
+	case *ast.ArrayType:
+		return a.compileArrayType(x);
+
+	case *ast.StructType:
+		goto notimpl;
+
+	case *ast.StarExpr:
+		return a.compilePtrType(x);
+
+	case *ast.FuncType:
+		return a.compileFuncType(x).Type;
+
+	case *ast.InterfaceType:
+		goto notimpl;
+
+	case *ast.MapType:
+		goto notimpl;
+
+	case *ast.ChanType:
+		goto notimpl;
+
+	case *ast.ParenExpr:
+		return a.compileType(x.X);
+
+	case *ast.Ellipsis:
+		a.diagAt(x, "illegal use of ellipsis");
+		return nil;
+	}
+	a.diagAt(x, "expression used as type");
+	return nil;
+
+notimpl:
+	a.diagAt(x, "compileType: %T not implemented", x);
+	return nil;
+}
+
+/*
+ * Type compiler interface
+ */
+
+func (a *compiler) compileType(scope *Scope, typ ast.Expr) Type {
+	tc := &typeCompiler{a, scope};
+	return tc.compileType(typ);
+}
+
+func (a *compiler) compileFuncType(scope *Scope, typ *ast.FuncType) *FuncDecl {
+	tc := &typeCompiler{a, scope};
+	return tc.compileFuncType(typ);
+}

usr/austin/eval/value.go

@@ -150,30 +150,29 @@ func (v *uintptrV) Set(x uint64) {
 }
 
 func (t *uintType) Zero() Value {
-	// TODO(austin) t may be a named type instead of one of the
-	// base types.
-	switch Type(t) {
-	case Uint8Type:
+	switch t.Bits {
+	case 0:
+		if t.Ptr {
+			res := uintptrV(0);
+			return &res;
+		} else {
+			res := uintV(0);
+			return &res;
+		}
+	case 8:
 		res := uint8V(0);
 		return &res;
-	case Uint16Type:
+	case 16:
 		res := uint16V(0);
 		return &res;
-	case Uint32Type:
+	case 32:
 		res := uint32V(0);
 		return &res;
-	case Uint64Type:
+	case 64:
 		res := uint64V(0);
 		return &res;
-
-	case UintType:
-		res := uintV(0);
-		return &res;
-	case UintptrType:
-		res := uintptrV(0);
-		return &res;
 	}
-	panic("unknown uint type ", t.String());
+	panic("unexpected uint bit count: ", t.Bits);
 }
 
 /*
@@ -271,25 +270,25 @@ func (v *intV) Set(x int64) {
 }
 
 func (t *intType) Zero() Value {
-	switch Type(t) {
-	case Int8Type:
+	switch t.Bits {
+	case 8:
 		res := int8V(0);
 		return &res;
-	case Int16Type:
+	case 16:
 		res := int16V(0);
 		return &res;
-	case Int32Type:
+	case 32:
 		res := int32V(0);
 		return &res;
-	case Int64Type:
+	case 64:
 		res := int64V(0);
 		return &res;
 
-	case IntType:
+	case 0:
 		res := intV(0);
 		return &res;
 	}
-	panic("unknown int type ", t.String());
+	panic("unexpected int bit count: ", t.Bits);
 }
 
 /*
@@ -375,18 +374,18 @@ func (v *floatV) Set(x float64) {
 }
 
 func (t *floatType) Zero() Value {
-	switch Type(t) {
-	case Float32Type:
+	switch t.Bits {
+	case 32:
 		res := float32V(0);
 		return &res;
-	case Float64Type:
+	case 64:
 		res := float64V(0);
 		return &res;
-	case FloatType:
+	case 0:
 		res := floatV(0);
 		return &res;
 	}
-	panic("unknown float type ", t.String());
+	panic("unexpected float bit count: ", t.Bits);
 }
 
 /*
@@ -505,6 +504,49 @@ func (v *ptrV) Set(x Value) {
 }
 
 func (t *PtrType) Zero() Value {
-	res := ptrV{nil};
-	return &res;
+	return &ptrV{nil};
+}
+
+/*
+ * Functions
+ */
+
+type funcV struct {
+	target Func;
+}
+
+func (v *funcV) String() string {
+	// TODO(austin) Rob wants to see the definition
+	return "func {...}";
+}
+
+func (v *funcV) Assign(o Value) {
+	v.target = o.(FuncValue).Get();
+}
+
+func (v *funcV) Get() Func {
+	return v.target;
+}
+
+func (v *funcV) Set(x Func) {
+	v.target = x;
+}
+
+func (t *FuncType) Zero() Value {
+	return &funcV{nil};
+}
+
+/*
+ * Universal constants
+ */
+
+// TODO(austin) Nothing complains if I accidentally define init with
+// arguments.  Is this intentional?
+func init() {
+	s := universe;
+
+	true := boolV(true);
+	s.DefineConst("true", BoolType, &true);
+	false := boolV(false);
+	s.DefineConst("false", BoolType, &false);
 }