qbit/go
1
0
Fork 0
mirror of https://github.com/golang/go synced 2024-11-21 11:04:40 -07:00
Code Releases Activity

tutorial: remove all line numbers and references to them.

Browse Source 
R=golang-dev, mikioh.mikioh, dsymonds
CC=golang-dev
https://golang.org/cl/4675070
This commit is contained in:
Rob Pike 2011-07-09 23:17:38 +10:00
parent ab3365d34e
commit c17347eea9
2 changed files with 50 additions and 52 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

82
doc/go_tutorial.html
View File

@ -19,9 +19,6 @@ The presentation here proceeds through a series of modest programs to illustrate
key features of the language. All the programs work (at time of writing) and are
checked into the repository in the directory <a href='/doc/progs'><code>/doc/progs/</code></a>.
<p>
Program snippets are annotated with the line number in the original file; for
cleanliness, blank lines remain blank.
<p>
<h2>Hello, World</h2>
<p>
Let's start in the usual way:
@ -29,7 +26,7 @@ Let's start in the usual way:
<pre><!-- progs/helloworld.go /package/ $
-->package main
import fmt &#34;fmt&#34; // Package implementing formatted I/O.
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;)
@ -121,18 +118,18 @@ Next up, here's a version of the Unix utility <code>echo(1)</code>:
import (
&#34;os&#34;
&#34;flag&#34; // command line option parser
&#34;flag&#34; // command line option parser
)
var omitNewline = flag.Bool(&#34;n&#34;, false, &#34;don&#39;t print final newline&#34;)
const (
Space = &#34; &#34;
Space = &#34; &#34;
Newline = &#34;\n&#34;
)
func main() {
flag.Parse() // Scans the arg list and sets up flags
flag.Parse() // Scans the arg list and sets up flags
var s string = &#34;&#34;
for i := 0; i &lt; flag.NArg(); i++ {
if i &gt; 0 {
@ -176,12 +173,13 @@ a naming conflict.
<p>
Given <code>os.Stdout</code> we can use its <code>WriteString</code> method to print the string.
<p>
Having imported the <code>flag</code> package, line 12 creates a global variable to hold
the value of echo's <code>-n</code> flag. The variable <code>omitNewline</code> has type <code>*bool</code>, pointer
to <code>bool</code>.
After importing the <code>flag</code> package, we use a <code>var</code> declaration
to create and initialize a global variable, called <code>omitNewline</code>,
to hold the value of echo's <code>-n</code> flag.
The variable has type <code>*bool</code>, pointer to <code>bool</code>.
<p>
In <code>main.main</code>, we parse the arguments (line 20) and then create a local
string variable we will use to build the output.
In <code>main.main</code>, we parse the arguments (the call to <code>flag.Parse</code>) and then create a local
string variable with which to build the output.
<p>
The declaration statement has the form
<p>
@ -261,7 +259,9 @@ reassigning it. This snippet from <code>strings.go</code> is legal code:
<p>
<pre><!-- progs/strings.go /hello/ /ciao/
--> s := &#34;hello&#34;
if s[1] != 'e' { os.Exit(1) }
if s[1] != 'e' {
os.Exit(1)
}
s = &#34;good bye&#34;
var p *string = &amp;s
*p = &#34;ciao&#34;
@ -540,7 +540,7 @@ return n
</pre>
<p>
but for simple structures like <code>File</code> it's easier to return the address of a
composite literal, as is done here on line 21.
composite literal, as is done here in the <code>return</code> statement from <code>newFile</code>.
<p>
We can use the factory to construct some familiar, exported variables of type <code>*File</code>:
<p>
@ -573,9 +573,9 @@ multi-value return as a parenthesized list of declarations; syntactically
they look just like a second parameter list. The function
<code>syscall.Open</code>
also has a multi-value return, which we can grab with the multi-variable
declaration on line 31; it declares <code>r</code> and <code>e</code> to hold the two values,
declaration on the first line; it declares <code>r</code> and <code>e</code> to hold the two values,
both of type <code>int</code> (although you'd have to look at the <code>syscall</code> package
to see that). Finally, line 35 returns two values: a pointer to the new <code>File</code>
to see that). Finally, <code>OpenFile</code> returns two values: a pointer to the new <code>File</code>
and the error. If <code>syscall.Open</code> fails, the file descriptor <code>r</code> will
be negative and <code>newFile</code> will return <code>nil</code>.
<p>
@ -689,7 +689,7 @@ func main() {
file.Stdout.Write(hello)
f, err := file.Open(&#34;/does/not/exist&#34;)
if f == nil {
fmt.Printf(&#34;can&#39;t open file; err=%s\n&#34;, err.String())
fmt.Printf(&#34;can&#39;t open file; err=%s\n&#34;, err.String())
os.Exit(1)
}
}
@ -938,9 +938,9 @@ arrays of integers, strings, etc.; here's the code for arrays of <code>int</code
<pre><!-- progs/sort.go /type.*IntSlice/ /Swap/
-->type IntSlice []int
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] }
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>
<p>
Here we see methods defined for non-<code>struct</code> types. You can define methods
@ -966,18 +966,18 @@ to implement the three methods for that type, like this:
<p>
<pre><!-- progs/sortmain.go /type.day/ /Swap/
-->type day struct {
num int
shortName string
longName string
num int
shortName string
longName string
}
type dayArray struct {
data []*day
}
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] }
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>
<p>
<p>
@ -1013,7 +1013,7 @@ 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><!-- progs/print.go 10 11
--> var u64 uint64 = 1&lt;&lt;64-1
--> var u64 uint64 = 1&lt;&lt;64 - 1
fmt.Printf(&#34;%d %d\n&#34;, u64, int64(u64))
</pre>
<p>
@ -1183,7 +1183,7 @@ Here is the first function in <code>progs/sieve.go</code>:
-->// Send the sequence 2, 3, 4, ... to channel 'ch'.
func generate(ch chan int) {
for i := 2; ; i++ {
ch &lt;- i // Send &#39;i&#39; to channel &#39;ch&#39;.
ch &lt;- i // Send &#39;i&#39; to channel &#39;ch&#39;.
}
}
</pre>
@ -1203,9 +1203,9 @@ operator <code>&lt;-</code> (receive) retrieves the next value on the channel.
// removing those divisible by 'prime'.
func filter(in, out chan int, prime int) {
for {
i := &lt;-in // Receive value of new variable &#39;i&#39; from &#39;in&#39;.
if i % prime != 0 {
out &lt;- i // Send &#39;i&#39; to channel &#39;out&#39;.
i := &lt;-in // Receive value of new variable &#39;i&#39; from &#39;in&#39;.
if i%prime != 0 {
out &lt;- i // Send &#39;i&#39; to channel &#39;out&#39;.
}
}
}
@ -1238,8 +1238,8 @@ together:
<p>
<pre><!-- progs/sieve.go /func.main/ /^}/
-->func main() {
ch := make(chan int) // Create a new channel.
go generate(ch) // Start generate() as a goroutine.
ch := make(chan int) // Create a new channel.
go generate(ch) // Start generate() as a goroutine.
for i := 0; i &lt; 100; i++ { // Print the first hundred primes.
prime := &lt;-ch
fmt.Println(prime)
@ -1262,7 +1262,7 @@ of <code>generate</code>, from <code>progs/sieve1.go</code>:
<pre><!-- progs/sieve1.go /func.generate/ /^}/
-->func generate() chan int {
ch := make(chan int)
go func(){
go func() {
for i := 2; ; i++ {
ch &lt;- i
}
@ -1288,7 +1288,7 @@ The same change can be made to <code>filter</code>:
out := make(chan int)
go func() {
for {
if i := &lt;-in; i % prime != 0 {
if i := &lt;-in; i%prime != 0 {
out &lt;- i
}
}
@ -1337,8 +1337,8 @@ that will be used for the reply.
<p>
<pre><!-- progs/server.go /type.request/ /^}/
-->type request struct {
a, b int
replyc chan int
a, b int
replyc chan int
}
</pre>
<p>
@ -1364,7 +1364,7 @@ a long-running operation, starting a goroutine to do the actual work.
-->func server(op binOp, service chan *request) {
for {
req := &lt;-service
go run(op, req) // don't wait for it
go run(op, req) // don't wait for it
}
}
</pre>
@ -1396,8 +1396,8 @@ does it check the results.
req.replyc = make(chan int)
adder &lt;- req
}
for i := N-1; i &gt;= 0; i-- { // doesn&#39;t matter what order
if &lt;-reqs[i].replyc != N + 2*i {
for i := N - 1; i &gt;= 0; i-- { // doesn&#39;t matter what order
if &lt;-reqs[i].replyc != N+2*i {
fmt.Println(&#34;fail at&#34;, i)
}
}
@ -1425,7 +1425,7 @@ It passes the quit channel to the <code>server</code> function, which uses it li
for {
select {
case req := &lt;-service:
go run(op, req) // don't wait for it
go run(op, req) // don't wait for it
case &lt;-quit:
return
}

20
doc/go_tutorial.txt
View File

@ -20,9 +20,6 @@ The presentation here proceeds through a series of modest programs to illustrate
key features of the language. All the programs work (at time of writing) and are
checked into the repository in the directory <a href='/doc/progs'>"/doc/progs/"</a>.
Program snippets are annotated with the line number in the original file; for
cleanliness, blank lines remain blank.
Hello, World
----
@ -136,12 +133,13 @@ a naming conflict.
Given "os.Stdout" we can use its "WriteString" method to print the string.
Having imported the "flag" package, line 12 creates a global variable to hold
the value of echo's "-n" flag. The variable "omitNewline" has type "*bool", pointer
to "bool".
After importing the "flag" package, we use a "var" declaration
to create and initialize a global variable, called "omitNewline",
to hold the value of echo's "-n" flag.
The variable has type "*bool", pointer to "bool".
In "main.main", we parse the arguments (line 20) and then create a local
string variable we will use to build the output.
In "main.main", we parse the arguments (the call to "flag.Parse") and then create a local
string variable with which to build the output.
The declaration statement has the form
@ -429,7 +427,7 @@ object. We could write
return n
but for simple structures like "File" it's easier to return the address of a
composite literal, as is done here on line 21.
composite literal, as is done here in the "return" statement from "newFile".
We can use the factory to construct some familiar, exported variables of type "*File":
@ -447,9 +445,9 @@ multi-value return as a parenthesized list of declarations; syntactically
they look just like a second parameter list. The function
"syscall.Open"
also has a multi-value return, which we can grab with the multi-variable
declaration on line 31; it declares "r" and "e" to hold the two values,
declaration on the first line; it declares "r" and "e" to hold the two values,
both of type "int" (although you'd have to look at the "syscall" package
to see that). Finally, line 35 returns two values: a pointer to the new "File"
to see that). Finally, "OpenFile" returns two values: a pointer to the new "File"
and the error. If "syscall.Open" fails, the file descriptor "r" will
be negative and "newFile" will return "nil".