math/bits: examples generator

Change-Id: Icdd0566d3b7dbc034256e16f8a6b6f1af07069b3
Reviewed-on: https://go-review.googlesource.com/54350Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/math/bits/example_test.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// Code generated by go run make_examples.go. DO NOT EDIT.
+
 package bits_test
 
 import (
@@ -33,52 +35,52 @@ func ExampleLeadingZeros64() {
 	// LeadingZeros64(0000000000000000000000000000000000000000000000000000000000000001) = 63
 }
 
-func ExampleOnesCount8() {
-	fmt.Printf("OnesCount8(%08b) = %d\n", 14, bits.OnesCount8(14))
+func ExampleTrailingZeros8() {
+	fmt.Printf("TrailingZeros8(%08b) = %d\n", 14, bits.TrailingZeros8(14))
 	// Output:
-	// OnesCount8(00001110) = 3
+	// TrailingZeros8(00001110) = 1
 }
 
-func ExampleOnesCount16() {
-	fmt.Printf("OnesCount16(%016b) = %d\n", 14, bits.OnesCount16(14))
+func ExampleTrailingZeros16() {
+	fmt.Printf("TrailingZeros16(%016b) = %d\n", 14, bits.TrailingZeros16(14))
 	// Output:
-	// OnesCount16(0000000000001110) = 3
+	// TrailingZeros16(0000000000001110) = 1
 }
 
-func ExampleOnesCount32() {
-	fmt.Printf("OnesCount32(%032b) = %d\n", 14, bits.OnesCount32(14))
+func ExampleTrailingZeros32() {
+	fmt.Printf("TrailingZeros32(%032b) = %d\n", 14, bits.TrailingZeros32(14))
 	// Output:
-	// OnesCount32(00000000000000000000000000001110) = 3
+	// TrailingZeros32(00000000000000000000000000001110) = 1
 }
 
-func ExampleOnesCount64() {
-	fmt.Printf("OnesCount64(%064b) = %d\n", 14, bits.OnesCount64(14))
+func ExampleTrailingZeros64() {
+	fmt.Printf("TrailingZeros64(%064b) = %d\n", 14, bits.TrailingZeros64(14))
 	// Output:
-	// OnesCount64(0000000000000000000000000000000000000000000000000000000000001110) = 3
+	// TrailingZeros64(0000000000000000000000000000000000000000000000000000000000001110) = 1
 }
 
-func ExampleTrailingZeros8() {
-	fmt.Printf("TrailingZeros8(%08b) = %d\n", 8, bits.TrailingZeros8(8))
+func ExampleOnesCount8() {
+	fmt.Printf("OnesCount8(%08b) = %d\n", 14, bits.OnesCount8(14))
 	// Output:
-	// TrailingZeros8(00001000) = 3
+	// OnesCount8(00001110) = 3
 }
 
-func ExampleTrailingZeros16() {
-	fmt.Printf("TrailingZeros16(%016b) = %d\n", 8, bits.TrailingZeros16(8))
+func ExampleOnesCount16() {
+	fmt.Printf("OnesCount16(%016b) = %d\n", 14, bits.OnesCount16(14))
 	// Output:
-	// TrailingZeros16(0000000000001000) = 3
+	// OnesCount16(0000000000001110) = 3
 }
 
-func ExampleTrailingZeros32() {
-	fmt.Printf("TrailingZeros32(%032b) = %d\n", 8, bits.TrailingZeros32(8))
+func ExampleOnesCount32() {
+	fmt.Printf("OnesCount32(%032b) = %d\n", 14, bits.OnesCount32(14))
 	// Output:
-	// TrailingZeros32(00000000000000000000000000001000) = 3
+	// OnesCount32(00000000000000000000000000001110) = 3
 }
 
-func ExampleTrailingZeros64() {
-	fmt.Printf("TrailingZeros64(%064b) = %d\n", 8, bits.TrailingZeros64(8))
+func ExampleOnesCount64() {
+	fmt.Printf("OnesCount64(%064b) = %d\n", 14, bits.OnesCount64(14))
 	// Output:
-	// TrailingZeros64(0000000000000000000000000000000000000000000000000000000000001000) = 3
+	// OnesCount64(0000000000000000000000000000000000000000000000000000000000001110) = 3
 }
 
 func ExampleLen8() {
@@ -105,6 +107,14 @@ func ExampleLen64() {
 	// Len64(0000000000000000000000000000000000000000000000000000000000001000) = 4
 }
 
+func ExampleReverse8() {
+	fmt.Printf("%08b\n", 19)
+	fmt.Printf("%08b\n", bits.Reverse8(19))
+	// Output:
+	// 00010011
+	// 11001000
+}
+
 func ExampleReverse16() {
 	fmt.Printf("%016b\n", 19)
 	fmt.Printf("%016b\n", bits.Reverse16(19))
@@ -128,11 +138,3 @@ func ExampleReverse64() {
 	// 0000000000000000000000000000000000000000000000000000000000010011
 	// 1100100000000000000000000000000000000000000000000000000000000000
 }
-
-func ExampleReverse8() {
-	fmt.Printf("%008b\n", 19)
-	fmt.Printf("%008b\n", bits.Reverse8(19))
-	// Output:
-	// 00010011
-	// 11001000
-}

src/math/bits/make_examples.go

+// Copyright 2017 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.
+
+// +build ignore
+
+// This program generates example_test.go.
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/format"
+	"io"
+	"io/ioutil"
+	"log"
+	"math/bits"
+	"sort"
+)
+
+var (
+	header = []byte(`// Copyright 2017 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.
+
+// Code generated by go run make_examples.go. DO NOT EDIT.
+
+package bits_test
+
+import (
+	"fmt"
+	"math/bits"
+)
+
+`)
+
+	exampleRegF = `
+func Example%s() {
+	fmt.Printf("%s\n", %d, bits.%s(%d))
+	// Output:
+	// %s
+}
+`
+	exampleRevF = `
+func Example%s() {
+	fmt.Printf("%s\n", %d)
+	fmt.Printf("%s\n", bits.%s(%d))
+	// Output:
+	// %s
+	// %s
+}
+`
+)
+
+func main() {
+	buf := bytes.NewBuffer(header)
+
+	genReg(buf)
+	genRev(buf)
+
+	out, err := format.Source(buf.Bytes())
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	err = ioutil.WriteFile("example_test.go", out, 0666)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func genReg(w io.Writer) {
+	examples := []struct {
+		name string
+		in   int
+		out  map[uint]interface{}
+	}{
+		{
+			name: "LeadingZeros",
+			in:   1,
+			out: map[uint]interface{}{
+				8:  bits.LeadingZeros8(1),
+				16: bits.LeadingZeros16(1),
+				32: bits.LeadingZeros32(1),
+				64: bits.LeadingZeros64(1),
+			},
+		}, {
+			name: "TrailingZeros",
+			in:   14,
+			out: map[uint]interface{}{
+				8:  bits.TrailingZeros8(14),
+				16: bits.TrailingZeros16(14),
+				32: bits.TrailingZeros32(14),
+				64: bits.TrailingZeros64(14),
+			},
+		}, {
+			name: "OnesCount",
+			in:   14,
+			out: map[uint]interface{}{
+				8:  bits.OnesCount8(14),
+				16: bits.OnesCount16(14),
+				32: bits.OnesCount32(14),
+				64: bits.OnesCount64(14),
+			},
+		}, {
+			name: "Len",
+			in:   8,
+			out: map[uint]interface{}{
+				8:  bits.Len8(8),
+				16: bits.Len16(8),
+				32: bits.Len32(8),
+				64: bits.Len64(8),
+			},
+		},
+	}
+
+	for _, e := range examples {
+		sizes := sortedSizes(e.out)
+
+		for _, size := range sizes {
+			fnName := fmt.Sprintf("%s%d", e.name, size)
+			outF := fmt.Sprintf("%s(%%0%db) = %%d", fnName, size)
+			out := fmt.Sprintf(outF, e.in, e.out[size])
+
+			fmt.Fprintf(w, exampleRegF, fnName, outF, e.in, fnName, e.in, out)
+		}
+	}
+}
+
+func genRev(w io.Writer) {
+	examples := []struct {
+		name string
+		in   int
+		out  map[uint]interface{}
+	}{
+		{
+			name: "Reverse",
+			in:   19,
+			out: map[uint]interface{}{
+				8:  bits.Reverse8(19),
+				16: bits.Reverse16(19),
+				32: bits.Reverse32(19),
+				64: bits.Reverse64(19),
+			},
+		},
+	}
+
+	for _, e := range examples {
+		sizes := sortedSizes(e.out)
+
+		for _, size := range sizes {
+			fnName := fmt.Sprintf("%s%d", e.name, size)
+			outF := fmt.Sprintf("%%0%db", size)
+			out := fmt.Sprintf(outF, e.in)
+			secOut := fmt.Sprintf(outF, e.out[size])
+
+			fmt.Fprintf(w, exampleRevF, fnName, outF, e.in, outF, fnName, e.in, out, secOut)
+		}
+	}
+}
+
+func sortedSizes(out map[uint]interface{}) []uint {
+	sizes := make([]uint, 0, len(out))
+	for size := range out {
+		sizes = append(sizes, size)
+	}
+
+	sort.Slice(sizes, func(i, j int) bool {
+		return sizes[i] < sizes[j]
+	})
+
+	return sizes
+}