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Commit 5353e1ef authored by Andrew Gerrand's avatar Andrew Gerrand
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doc: trim spaces from code snippets 

gofmt likes to put lines like
  // STOP OMIT
two blank lines from a closing brace, creating an ugly space inside
<pre> blocks in some of these files. This change resolves this issue.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/5520044
parent 5f5a7eb4
Show whitespace changes
Inline Side-by-side
Showing with 102 additions and 185 deletions
doc/articles/defer_panic_recover.html
View file @ 5353e1ef
......@@ -37,8 +37,7 @@ contents of one file to the other:
dst.Close()
src.Close()
return
}
</pre>
}</pre>
<p>
This works, but there is a bug. If the second call to os.Open fails, the
......@@ -64,8 +63,7 @@ files are always closed:
defer dst.Close()
return io.Copy(dst, src)
}
</pre>
}</pre>
<p>
Defer statements allow us to think about closing each file right after opening
......@@ -94,8 +92,7 @@ deferred. The deferred call will print "0" after the function returns.
defer fmt.Println(i)
i++
return
}
</pre>
}</pre>
<p>
2. <i>Deferred function calls are executed in Last In First Out order
......@@ -111,8 +108,7 @@ This function prints "3210":
for i := 0; i &lt; 4; i++ {
defer fmt.Print(i)
}
}
</pre>
}</pre>
<p>
3. <i>Deferred functions may read and assign to the returning function's named
......@@ -128,8 +124,7 @@ the surrounding function returns. Thus, this function returns 2:
-->func c() (i int) {
defer func() { i++ }()
return 1
}
</pre>
}</pre>
<p>
This is convenient for modifying the error return value of a function; we will
......@@ -188,8 +183,7 @@ func g(i int) {
defer fmt.Println(&#34;Defer in g&#34;, i)
fmt.Println(&#34;Printing in g&#34;, i)
g(i + 1)
}
</pre>
}</pre>
<p>
The function g takes the int i, and panics if i is greater than 3, or else it
......
doc/articles/error_handling.html
View file @ 5353e1ef
......@@ -12,8 +12,7 @@ returns a non-nil <code>error</code> value when it fails to open a file.
</p>
<pre><!--{{code "progs/error.go" `/func Open/`}}
-->func Open(name string) (file *File, err error)
</pre>
-->func Open(name string) (file *File, err error)</pre>
<p>
The following code uses <code>os.Open</code> to open a file. If an error
......@@ -21,12 +20,11 @@ occurs it calls <code>log.Fatal</code> to print the error message and stop.
</p>
<pre><!--{{code "progs/error.go" `/func openFile/` `/STOP/`}}
--> f, err := os.Open(&#34;filename.ext&#34;)
-->f, err := os.Open(&#34;filename.ext&#34;)
if err != nil {
log.Fatal(err)
}
// do something with the open *File f
</pre>
// do something with the open *File f</pre>
<p>
You can get a lot done in Go knowing just this about the <code>error</code>
......@@ -67,8 +65,7 @@ type errorString struct {
func (e *errorString) Error() string {
return e.s
}
</pre>
}</pre>
<p>
You can construct one of these values with the <code>errors.New</code>
......@@ -80,8 +77,7 @@ and returns as an <code>error</code> value.
-->// New returns an error that formats as the given text.
func New(text string) error {
return &amp;errorString{text}
}
</pre>
}</pre>
<p>
Here's how you might use <code>errors.New</code>:
......@@ -93,8 +89,7 @@ Here's how you might use <code>errors.New</code>:
return 0, errors.New(&#34;math: square root of negative number&#34;)
}
// implementation
}
</pre>
}</pre>
<p>
A caller passing a negative argument to <code>Sqrt</code> receives a non-nil
......@@ -105,11 +100,10 @@ A caller passing a negative argument to <code>Sqrt</code> receives a non-nil
</p>
<pre><!--{{code "progs/error.go" `/func printErr/` `/STOP/`}}
--> f, err := Sqrt(-1)
-->f, err := Sqrt(-1)
if err != nil {
fmt.Println(err)
}
</pre>
}</pre>
<p>
The <a href="/pkg/fmt/">fmt</a> package formats an <code>error</code> value
......@@ -131,10 +125,9 @@ rules and returns it as an <code>error</code> created by
</p>
<pre><!--{{code "progs/error.go" `/fmtError/` `/STOP/`}}
--> if f &lt; 0 {
-->if f &lt; 0 {
return 0, fmt.Errorf(&#34;math: square root of negative number %g&#34;, f)
}
</pre>
}</pre>
<p>
In many cases <code>fmt.Errorf</code> is good enough, but since
......@@ -153,8 +146,7 @@ error implementation instead of using <code>errors.errorString</code>:
func (f NegativeSqrtError) Error() string {
return fmt.Sprintf(&#34;math: square root of negative number %g&#34;, float64(f))
}
</pre>
}</pre>
<p>
A sophisticated caller can then use a
......@@ -176,8 +168,7 @@ returns when it encounters a syntax error parsing a JSON blob.
Offset int64 // error occurred after reading Offset bytes
}
func (e *SyntaxError) Error() string { return e.msg }
</pre>
func (e *SyntaxError) Error() string { return e.msg }</pre>
<p>
The <code>Offset</code> field isn't even shown in the default formatting of the
......@@ -186,14 +177,13 @@ messages:
</p>
<pre><!--{{code "progs/error.go" `/func decodeError/` `/STOP/`}}
--> if err := dec.Decode(&amp;val); err != nil {
-->if err := dec.Decode(&amp;val); err != nil {
if serr, ok := err.(*json.SyntaxError); ok {
line, col := findLine(f, serr.Offset)
return fmt.Errorf(&#34;%s:%d:%d: %v&#34;, f.Name(), line, col, err)
}
return err
}
</pre>
}</pre>
<p>
(This is a slightly simplified version of some
......@@ -226,14 +216,13 @@ up otherwise.
</p>
<pre><!--{{code "progs/error.go" `/func netError/` `/STOP/`}}
--> if nerr, ok := err.(net.Error); ok &amp;&amp; nerr.Temporary() {
-->if nerr, ok := err.(net.Error); ok &amp;&amp; nerr.Temporary() {
time.Sleep(1e9)
continue
}
if err != nil {
log.Fatal(err)
}
</pre>
}</pre>
<p>
<b>Simplifying repetitive error handling</b>
......@@ -269,8 +258,7 @@ func viewRecord(w http.ResponseWriter, r *http.Request) {
if err := viewTemplate.Execute(w, record); err != nil {
http.Error(w, err.Error(), 500)
}
}
</pre>
}</pre>
<p>
This function handles errors returned by the <code>datastore.Get</code>
......@@ -287,8 +275,7 @@ type that includes an <code>error</code> return value:
</p>
<pre><!--{{code "progs/error3.go" `/type appHandler/`}}
-->type appHandler func(http.ResponseWriter, *http.Request) error
</pre>
-->type appHandler func(http.ResponseWriter, *http.Request) error</pre>
<p>
Then we can change our <code>viewRecord</code> function to return errors:
......@@ -303,8 +290,7 @@ Then we can change our <code>viewRecord</code> function to return errors:
return err
}
return viewTemplate.Execute(w, record)
}
</pre>
}</pre>
<p>
This is simpler than the original version, but the <a
......@@ -319,8 +305,7 @@ To fix this we can implement the <code>http.Handler</code> interface's
if err := fn(w, r); err != nil {
http.Error(w, err.Error(), 500)
}
}
</pre>
}</pre>
<p>
The <code>ServeHTTP</code> method calls the <code>appHandler</code> function
......@@ -339,8 +324,7 @@ Now when registering <code>viewRecord</code> with the http package we use the
<pre><!--{{code "progs/error3.go" `/func init/` `/STOP/`}}
-->func init() {
http.Handle(&#34;/view&#34;, appHandler(viewRecord))
}
</pre>
}</pre>
<p>
With this basic error handling infrastructure in place, we can make it more
......@@ -360,16 +344,14 @@ To do this we create an <code>appError</code> struct containing an
Error error
Message string
Code int
}
</pre>
}</pre>
<p>
Next we modify the appHandler type to return <code>*appError</code> values:
</p>
<pre><!--{{code "progs/error4.go" `/type appHandler/`}}
-->type appHandler func(http.ResponseWriter, *http.Request) *appError
</pre>
-->type appHandler func(http.ResponseWriter, *http.Request) *appError</pre>
<p>
(It's usually a mistake to pass back the concrete type of an error rather than
......@@ -392,8 +374,7 @@ console:
c.Errorf(&#34;%v&#34;, e.Error)
http.Error(w, e.Message, e.Code)
}
}
</pre>
}</pre>
<p>
Finally, we update <code>viewRecord</code> to the new function signature and
......@@ -412,8 +393,7 @@ have it return more context when it encounters an error:
return &amp;appError{err, &#34;Can&#39;t display record&#34;, 500}
}
return nil
}
</pre>
}</pre>
<p>
This version of <code>viewRecord</code> is the same length as the original, but
......
doc/effective_go.html
View file @ 5353e1ef
......@@ -1690,8 +1690,7 @@ const (
EB
ZB
YB
)
</pre>
)</pre>
<p>
The ability to attach a method such as <code>String</code> to a
type makes it possible for such values to format themselves
......@@ -1718,8 +1717,7 @@ automatically for printing, even as part of a general type.
return fmt.Sprintf(&#34;%.2fKB&#34;, float64(b/KB))
}
return fmt.Sprintf(&#34;%.2fB&#34;, float64(b))
}
</pre>
}</pre>
<p>
(The <code>float64</code> conversions prevent <code>Sprintf</code>
from recurring back through the <code>String</code> method for
......@@ -1893,8 +1891,7 @@ func (s Sequence) String() string {
str += fmt.Sprint(elem)
}
return str + &#34;]&#34;
}
</pre>
}</pre>
<h3 id="conversions">Conversions</h3>
......@@ -3044,8 +3041,7 @@ value=&#34;Show QR&#34; name=qr&gt;
&lt;/form&gt;
&lt;/body&gt;
&lt;/html&gt;
`
</pre>
`</pre>
<p>
The pieces up to <code>main</code> should be easy to follow.
The one flag sets a default HTTP port for our server. The template
......
doc/go1.html
View file @ 5353e1ef
......@@ -44,9 +44,8 @@ call.
</p>
<pre><!--{{code "progs/go1.go" `/greeting := ..byte/` `/append.*hello/`}}
--> greeting := []byte{}
greeting = append(greeting, []byte(&#34;hello &#34;)...)
</pre>
-->greeting := []byte{}
greeting = append(greeting, []byte(&#34;hello &#34;)...)</pre>
<p>
By analogy with the similar property of <code>copy</code>, Go 1
......@@ -55,8 +54,7 @@ slice; the conversion is no longer necessary:
</p>
<pre><!--{{code "progs/go1.go" `/append.*world/`}}
--> greeting = append(greeting, &#34;world&#34;...)
</pre>
-->greeting = append(greeting, &#34;world&#34;...)</pre>
<p>
<em>Updating</em>:
......@@ -97,7 +95,7 @@ All four of the initializations in this example are legal; the last one was ille
</p>
<pre><!--{{code "progs/go1.go" `/type Date struct/` `/STOP/`}}
--> type Date struct {
-->type Date struct {
month string
day int
}
......@@ -124,8 +122,7 @@ All four of the initializations in this example are legal; the last one was ille
{&#34;Feb&#34;, 14},
{&#34;Nov&#34;, 11},
{&#34;Dec&#34;, 25},
}
</pre>
}</pre>
<p>
<em>Updating</em>:
......@@ -152,8 +149,7 @@ func init() {
c := make(chan int)
go initializationFunction(c)
PackageGlobal = &lt;-c
}
</pre>
}</pre>
<p>
<em>Updating</em>:
......@@ -186,14 +182,13 @@ relatives now take and return a <code>rune</code>.
</p>
<pre><!--{{code "progs/go1.go" `/STARTRUNE/` `/ENDRUNE/`}}
--> delta := &#39;δ&#39; // delta has type rune.
-->delta := &#39;δ&#39; // delta has type rune.
var DELTA rune
DELTA = unicode.ToUpper(delta)
epsilon := unicode.ToLower(DELTA + 1)
if epsilon != &#39;δ&#39;+1 {
log.Fatal(&#34;inconsistent casing for Greek&#34;)
}
</pre>
}</pre>
<p>
<em>Updating</em>:
......@@ -236,8 +231,7 @@ function, <code>delete</code>. The call
</p>
<pre><!--{{code "progs/go1.go" `/delete\(m, k\)/`}}
--> delete(m, k)
</pre>
-->delete(m, k)</pre>
<p>
will delete the map entry retrieved by the expression <code>m[k]</code>.
......@@ -264,12 +258,11 @@ Code should not assume that the elements are visited in any particular order.
</p>
<pre><!--{{code "progs/go1.go" `/Sunday/` `/^ }/`}}
--> m := map[string]int{&#34;Sunday&#34;: 0, &#34;Monday&#34;: 1}
-->m := map[string]int{&#34;Sunday&#34;: 0, &#34;Monday&#34;: 1}
for name, value := range m {
// This loop should not assume Sunday will be visited first.
f(name, value)
}
</pre>
}</pre>
<p>
<em>Updating</em>:
......@@ -299,7 +292,7 @@ These examples illustrate the behavior.
</p>
<pre><!--{{code "progs/go1.go" `/sa :=/` `/then sc.0. = 2/`}}
--> sa := []int{1, 2, 3}
-->sa := []int{1, 2, 3}
i := 0
i, sa[i] = 1, 2 // sets i = 1, sa[0] = 2
......@@ -308,8 +301,7 @@ These examples illustrate the behavior.
sb[j], j = 2, 1 // sets sb[0] = 2, j = 1
sc := []int{1, 2, 3}
sc[0], sc[0] = 1, 2 // sets sc[0] = 1, then sc[0] = 2 (so sc[0] = 2 at end)
</pre>
sc[0], sc[0] = 1, 2 // sets sc[0] = 1, then sc[0] = 2 (so sc[0] = 2 at end)</pre>
<p>
<em>Updating</em>:
......@@ -417,7 +409,7 @@ As a result, structs and arrays can now be used as map keys:
</p>
<pre><!--{{code "progs/go1.go" `/type Day struct/` `/Printf/`}}
--> type Day struct {
-->type Day struct {
long string
short string
}
......@@ -427,8 +419,7 @@ As a result, structs and arrays can now be used as map keys:
Christmas: true,
Thanksgiving: true,
}
fmt.Printf(&#34;Christmas is a holiday: %t\n&#34;, holiday[Christmas])
</pre>
fmt.Printf(&#34;Christmas is a holiday: %t\n&#34;, holiday[Christmas])</pre>
<p>
Note that equality is still undefined for slices, for which the
......@@ -575,8 +566,7 @@ does for <code>String</code>, for easy printing of error values.
func (se *SyntaxError) Error() string {
return fmt.Sprintf(&#34;%s:%d: %s&#34;, se.File, se.Line, se.Message)
}
</pre>
}</pre>
<p>
All standard packages have been updated to use the new interface; the old <code>os.Error</code> is gone.
......@@ -595,8 +585,7 @@ to turn a string into an error. It replaces the old <code>os.NewError</code>.
</p>
<pre><!--{{code "progs/go1.go" `/ErrSyntax/`}}
--> var ErrSyntax = errors.New(&#34;syntax error&#34;)
</pre>
-->var ErrSyntax = errors.New(&#34;syntax error&#34;)</pre>
<p>
<em>Updating</em>:
......@@ -677,8 +666,7 @@ func sleepUntil(wakeup time.Time) {
delta := wakeup.Sub(now) // A Duration.
log.Printf(&#34;Sleeping for %.3fs&#34;, delta.Seconds())
time.Sleep(delta)
}
</pre>
}</pre>
<p>
The new types, methods, and constants have been propagated through
......
doc/go_tutorial.html
View file @ 5353e1ef
......@@ -33,8 +33,7 @@ import fmt &#34;fmt&#34; // Package implementing formatted I/O.
func main() {
fmt.Printf(&#34;Hello, world; or Καλημέρα κόσμε; or こんにちは 世界\n&#34;)
}
</pre>
}</pre>
<p>
Every Go source file declares, using a <code>package</code> statement, which package it's part of.
It may also import other packages to use their facilities.
......@@ -144,8 +143,7 @@ func main() {
s += Newline
}
os.Stdout.WriteString(s)
}
</pre>
}</pre>
<p>
This program is small but it's doing a number of new things. In the last example,
we saw <code>func</code> introduce a function. The keywords <code>var</code>, <code>const</code>, and <code>type</code>
......@@ -211,8 +209,7 @@ The <code>:=</code> operator is used a lot in Go to represent an initializing de
There's one in the <code>for</code> clause on the next line:
<p>
<pre><!--{{code "progs/echo.go" `/for/`}}
--> for i := 0; i &lt; flag.NArg(); i++ {
</pre>
-->for i := 0; i &lt; flag.NArg(); i++ {</pre>
<p>
The <code>flag</code> package has parsed the arguments and left the non-flag arguments
in a list that can be iterated over in the obvious way.
......@@ -261,14 +258,13 @@ of course you can change a string <i>variable</i> simply by
reassigning it. This snippet from <code>strings.go</code> is legal code:
<p>
<pre><!--{{code "progs/strings.go" `/hello/` `/ciao/`}}
--> s := &#34;hello&#34;
-->s := &#34;hello&#34;
if s[1] != &#39;e&#39; {
os.Exit(1)
}
s = &#34;good bye&#34;
var p *string = &amp;s
*p = &#34;ciao&#34;
</pre>
*p = &#34;ciao&#34;</pre>
<p>
However the following statements are illegal because they would modify
a <code>string</code> value:
......@@ -340,8 +336,7 @@ Using slices one can write this function (from <code>sum.go</code>):
s += a[i]
}
return s
}
</pre>
}</pre>
<p>
Note how the return type (<code>int</code>) is defined for <code>sum</code> by stating it
after the parameter list.
......@@ -493,8 +488,7 @@ import (
type File struct {
fd int // file descriptor number
name string // file name at Open time
}
</pre>
}</pre>
<p>
The first few lines declare the name of the
package&mdash;<code>file</code>&mdash;and then import two packages. The <code>os</code>
......@@ -535,8 +529,7 @@ First, though, here is a factory to create a <code>File</code>:
return nil
}
return &amp;File{fd, name}
}
</pre>
}</pre>
<p>
This returns a pointer to a new <code>File</code> structure with the file descriptor and name
filled in. This code uses Go's notion of a ''composite literal'', analogous to
......@@ -560,8 +553,7 @@ We can use the factory to construct some familiar, exported variables of type <c
Stdin = newFile(syscall.Stdin, &#34;/dev/stdin&#34;)
Stdout = newFile(syscall.Stdout, &#34;/dev/stdout&#34;)
Stderr = newFile(syscall.Stderr, &#34;/dev/stderr&#34;)
)
</pre>
)</pre>
<p>
The <code>newFile</code> function was not exported because it's internal. The proper,
exported factory to use is <code>OpenFile</code> (we'll explain that name in a moment):
......@@ -570,8 +562,7 @@ exported factory to use is <code>OpenFile</code> (we'll explain that name in a m
-->func OpenFile(name string, mode int, perm uint32) (file *File, err error) {
r, err := syscall.Open(name, mode, perm)
return newFile(r, name), err
}
</pre>
}</pre>
<p>
There are a number of new things in these few lines. First, <code>OpenFile</code> returns
multiple values, a <code>File</code> and an error (more about errors in a moment).
......@@ -613,14 +604,12 @@ the tricky standard arguments to open and, especially, to create a file:
func Open(name string) (file *File, err error) {
return OpenFile(name, O_RDONLY, 0)
}
</pre>
}</pre>
<p>
<pre><!--{{code "progs/file.go" `/func.Create/` `/^}/`}}
-->func Create(name string) (file *File, err error) {
return OpenFile(name, O_RDWR|O_CREATE|O_TRUNC, 0666)
}
</pre>
}</pre>
<p>
Back to our main story.
Now that we can build <code>Files</code>, we can write methods for them. To declare
......@@ -657,8 +646,7 @@ func (file *File) Write(b []byte) (ret int, err error) {
func (file *File) String() string {
return file.name
}
</pre>
}</pre>
<p>
There is no implicit <code>this</code> and the receiver variable must be used to access
members of the structure. Methods are not declared within
......@@ -692,8 +680,7 @@ func main() {
fmt.Printf(&#34;can&#39;t open file; err=%s\n&#34;, err.Error())
os.Exit(1)
}
}
</pre>
}</pre>
<p>
The ''<code>./</code>'' in the import of ''<code>./file</code>'' tells the compiler
to use our own package rather than
......@@ -761,8 +748,7 @@ func main() {
cat(f)
f.Close()
}
}
</pre>
}</pre>
<p>
By now this should be easy to follow, but the <code>switch</code> statement introduces some
new features. Like a <code>for</code> loop, an <code>if</code> or <code>switch</code> can include an
......@@ -794,8 +780,7 @@ Here is code from <code>progs/cat_rot13.go</code>:
-->type reader interface {
Read(b []byte) (ret int, err error)
String() string
}
</pre>
}</pre>
<p>
Any type that has the two methods of <code>reader</code>&mdash;regardless of whatever
other methods the type may also have&mdash;is said to <i>implement</i> the
......@@ -827,16 +812,14 @@ func (r13 *rotate13) Read(b []byte) (ret int, err error) {
func (r13 *rotate13) String() string {
return r13.source.String()
}
// end of rotate13 implementation
</pre>
// end of rotate13 implementation</pre>
<p>
(The <code>rot13</code> function called in <code>Read</code> is trivial and not worth reproducing here.)
<p>
To use the new feature, we define a flag:
<p>
<pre><!--{{code "progs/cat_rot13.go" `/rot13Flag/`}}
-->var rot13Flag = flag.Bool(&#34;rot13&#34;, false, &#34;rot13 the input&#34;)
</pre>
-->var rot13Flag = flag.Bool(&#34;rot13&#34;, false, &#34;rot13 the input&#34;)</pre>
<p>
and use it from within a mostly unchanged <code>cat</code> function:
<p>
......@@ -863,8 +846,7 @@ and use it from within a mostly unchanged <code>cat</code> function:
}
}
}
}
</pre>
}</pre>
<p>
(We could also do the wrapping in <code>main</code> and leave <code>cat</code> mostly alone, except
for changing the type of the argument; consider that an exercise.)
......@@ -918,8 +900,7 @@ As an example, consider this simple sort algorithm taken from <code>progs/sort.g
data.Swap(j, j-1)
}
}
}
</pre>
}</pre>
<p>
The code needs only three methods, which we wrap into sort's <code>Interface</code>:
<p>
......@@ -928,8 +909,7 @@ The code needs only three methods, which we wrap into sort's <code>Interface</co
Len() int
Less(i, j int) bool
Swap(i, j int)
}
</pre>
}</pre>
<p>
We can apply <code>Sort</code> to any type that implements <code>Len</code>, <code>Less</code>, and <code>Swap</code>.
The <code>sort</code> package includes the necessary methods to allow sorting of
......@@ -940,8 +920,7 @@ arrays of integers, strings, etc.; here's the code for arrays of <code>int</code
func (p IntSlice) Len() int { return len(p) }
func (p IntSlice) Less(i, j int) bool { return p[i] &lt; p[j] }
func (p IntSlice) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
</pre>
func (p IntSlice) Swap(i, j int) { p[i], p[j] = p[j], p[i] }</pre>
<p>
Here we see methods defined for non-<code>struct</code> types. You can define methods
for any type you define and name in your package.
......@@ -958,8 +937,7 @@ to test that the result is sorted.
if !sort.IsSorted(a) {
panic(&#34;fail&#34;)
}
}
</pre>
}</pre>
<p>
If we have a new type we want to be able to sort, all we need to do is
to implement the three methods for that type, like this:
......@@ -977,8 +955,7 @@ type dayArray struct {
func (p *dayArray) Len() int { return len(p.data) }
func (p *dayArray) Less(i, j int) bool { return p.data[i].num &lt; p.data[j].num }
func (p *dayArray) Swap(i, j int) { p.data[i], p.data[j] = p.data[j], p.data[i] }
</pre>
func (p *dayArray) Swap(i, j int) { p.data[i], p.data[j] = p.data[j], p.data[i] }</pre>
<p>
<p>
<h2>Printing</h2>
......@@ -1013,9 +990,8 @@ can just say <code>%d</code>; <code>Printf</code> knows the size and signedness
integer and can do the right thing for you. The snippet
<p>
<pre><!--{{code "progs/print.go" 10 11}}
--> var u64 uint64 = 1&lt;&lt;64 - 1
fmt.Printf(&#34;%d %d\n&#34;, u64, int64(u64))
</pre>
-->var u64 uint64 = 1&lt;&lt;64 - 1
fmt.Printf(&#34;%d %d\n&#34;, u64, int64(u64))</pre>
<p>
prints
<p>
......@@ -1027,14 +1003,13 @@ In fact, if you're lazy the format <code>%v</code> will print, in a simple
appropriate style, any value, even an array or structure. The output of
<p>
<pre><!--{{code "progs/print.go" 14 20}}
--> type T struct {
-->type T struct {
a int
b string
}
t := T{77, &#34;Sunset Strip&#34;}
a := []int{1, 2, 3, 4}
fmt.Printf(&#34;%v %v %v\n&#34;, u64, t, a)
</pre>
fmt.Printf(&#34;%v %v %v\n&#34;, u64, t, a)</pre>
<p>
is
<p>
......@@ -1050,9 +1025,8 @@ and adds a newline. The output of each of these two lines is identical
to that of the <code>Printf</code> call above.
<p>
<pre><!--{{code "progs/print.go" 21 22}}
--> fmt.Print(u64, &#34; &#34;, t, &#34; &#34;, a, &#34;\n&#34;)
fmt.Println(u64, t, a)
</pre>
-->fmt.Print(u64, &#34; &#34;, t, &#34; &#34;, a, &#34;\n&#34;)
fmt.Println(u64, t, a)</pre>
<p>
If you have your own type you'd like <code>Printf</code> or <code>Print</code> to format,
just give it a <code>String</code> method that returns a string. The print
......@@ -1073,8 +1047,7 @@ func (t *testType) String() string {
func main() {
t := &amp;testType{77, &#34;Sunset Strip&#34;}
fmt.Println(t)
}
</pre>
}</pre>
<p>
Since <code>*testType</code> has a <code>String</code> method, the
default formatter for that type will use it and produce the output
......@@ -1200,8 +1173,7 @@ func generate(ch chan int) {
for i := 2; ; i++ {
ch &lt;- i // Send &#39;i&#39; to channel &#39;ch&#39;.
}
}
</pre>
}</pre>
<p>
The <code>generate</code> function sends the sequence 2, 3, 4, 5, ... to its
argument channel, <code>ch</code>, using the binary communications operator <code>&lt;-</code>.
......@@ -1223,8 +1195,7 @@ func filter(in, out chan int, prime int) {
out &lt;- i // Send &#39;i&#39; to channel &#39;out&#39;.
}
}
}
</pre>
}</pre>
<p>
The generator and filters execute concurrently. Go has
its own model of process/threads/light-weight processes/coroutines,
......@@ -1262,8 +1233,7 @@ together:
go filter(ch, ch1, prime)
ch = ch1
}
}
</pre>
}</pre>
<p>
The first line of <code>main</code> creates the initial channel to pass to <code>generate</code>, which it
then starts up. As each prime pops out of the channel, a new <code>filter</code>
......@@ -1283,8 +1253,7 @@ of <code>generate</code>, from <code>progs/sieve1.go</code>:
}
}()
return ch
}
</pre>
}</pre>
<p>
This version does all the setup internally. It creates the output
channel, launches a goroutine running a function literal, and
......@@ -1309,8 +1278,7 @@ The same change can be made to <code>filter</code>:
}
}()
return out
}
</pre>
}</pre>
<p>
The <code>sieve</code> function's main loop becomes simpler and clearer as a
result, and while we're at it let's turn it into a factory too:
......@@ -1327,8 +1295,7 @@ result, and while we're at it let's turn it into a factory too:
}
}()
return out
}
</pre>
}</pre>
<p>
Now <code>main</code>'s interface to the prime sieve is a channel of primes:
<p>
......@@ -1338,8 +1305,7 @@ Now <code>main</code>'s interface to the prime sieve is a channel of primes:
for i := 0; i &lt; 100; i++ { // Print the first hundred primes.
fmt.Println(&lt;-primes)
}
}
</pre>
}</pre>
<p>
<h2>Multiplexing</h2>
<p>
......@@ -1354,8 +1320,7 @@ that will be used for the reply.
-->type request struct {
a, b int
replyc chan int
}
</pre>
}</pre>
<p>
The server will be trivial: it will do simple binary operations on integers. Here's the
code that invokes the operation and responds to the request:
......@@ -1366,8 +1331,7 @@ code that invokes the operation and responds to the request:
func run(op binOp, req *request) {
reply := op(req.a, req.b)
req.replyc &lt;- reply
}
</pre>
}</pre>
<p>
The type declaration makes <code>binOp</code> represent a function taking two integers and
returning a third.
......@@ -1381,8 +1345,7 @@ a long-running operation, starting a goroutine to do the actual work.
req := &lt;-service
go run(op, req) // don&#39;t wait for it
}
}
</pre>
}</pre>
<p>
There's a new feature in the signature of <code>server</code>: the type of the
<code>service</code> channel specifies the direction of communication.
......@@ -1403,8 +1366,7 @@ connected to it:
req := make(chan *request)
go server(op, req)
return req
}
</pre>
}</pre>
<p>
The returned channel is send only, even though the channel was created bidirectionally.
The read end is passed to <code>server</code>, while the send end is returned
......@@ -1441,8 +1403,7 @@ does it check the results.
}
}
fmt.Println(&#34;done&#34;)
}
</pre>
}</pre>
<p>
One annoyance with this program is that it doesn't shut down the server cleanly; when <code>main</code> returns
there are a number of lingering goroutines blocked on communication. To solve this,
......@@ -1454,8 +1415,7 @@ we can provide a second, <code>quit</code> channel to the server:
quit = make(chan bool)
go server(op, service, quit)
return service, quit
}
</pre>
}</pre>
<p>
It passes the quit channel to the <code>server</code> function, which uses it like this:
<p>
......@@ -1469,8 +1429,7 @@ It passes the quit channel to the <code>server</code> function, which uses it li
return
}
}
}
</pre>
}</pre>
<p>
Inside <code>server</code>, the <code>select</code> statement chooses which of the multiple communications
listed by its cases can proceed. If all are blocked, it waits until one can proceed; if
......@@ -1483,12 +1442,10 @@ All that's left is to strobe the <code>quit</code> channel
at the end of main:
<p>
<pre><!--{{code "progs/server1.go" `/adder,.quit/`}}
--> adder, quit := startServer(func(a, b int) int { return a + b })
</pre>
-->adder, quit := startServer(func(a, b int) int { return a + b })</pre>
...
<pre><!--{{code "progs/server1.go" `/quit....true/`}}
--> quit &lt;- true
</pre>
-->quit &lt;- true</pre>
<p>
There's a lot more to Go programming and concurrent programming in general but this
quick tour should give you some of the basics.
doc/tmpltohtml.go
View file @ 5353e1ef
......@@ -113,6 +113,8 @@ func code(file string, arg ...interface{}) (string, error) {
default:
return "", fmt.Errorf("incorrect code invocation: code %q %q", file, arg)
}
// Trim spaces from output.
text = strings.TrimSpace(text)
// Replace tabs by spaces, which work better in HTML.
text = strings.Replace(text, "\t", " ", -1)
// Escape the program text for HTML.
......
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