code review 5697063: doc: improve go_for_cpp_programmers & contribute

doc/go_for_cpp_programmers.html

 <!--{
 "Title": "Go For C++ Programmers"
 }-->
 
 <p>
 Go is a systems programming language intended to be a general-purpose
 systems language, like C++.
 These are some notes on Go for experienced C++ programmers. This
 document discusses the differences between Go and C++, and says little
 to nothing about the similarities.
@@ skipping 689 matching lines @@
 To use <code>manager2</code>, given a channel to it:
 
 <pre>
 func f4(ch &lt;- chan cmd2) int {
 myCh := make(chan int)
 c := cmd2{ true, 0, myCh } // Composite literal syntax.
 ch &lt;- c
 return &lt;-myCh
 }
 </pre>
+
+<h2 id="Appendix">Appendix</h2>
+<h3 id="First time pitfall">First Taste Pitfall</h3>
+
+<h4><a href="go_spec.html#Semicolons">Semicolons omit rule</a>.
+See <a href="#Syntax">Syntax</a>.
+</h4>
+<pre>
+func main() // compile error
+{
+...
+}
+func main() { // OK
+...
+}
+if x {
+} // compile error
+else {
+}
+</pre>
+
+<h4><a href="go_spec.html#Semicolons">
+Separate long line into multi line by operator</a></h4>
+<pre>
+s := "line1 \ // compile error
+line2"
+s := "line1" // compile error
++ "line2"
+s := "line1" + // use operator, OK
+"line2"
+s := `line1 // use backquote, OK
+line2`
+// string contain backquote(`) should use '+' or function to replace
+s := "...`..." // method 1, compile time decide
+s := strings.Replace(`...X....`,"X","'",-1) // method 2, runtime replace
+</pre>
+<h4>type cast</h4>
+<ul>
+<li>convert float to []byte by <a href="../pkg/encoding/binary/#Write">binary</a ></li>
+</ul>
+<h4>array declaration, reference <a href="#Syntax">Syntax</a></h4>
+For multiple dimension use following trick for speedup,·
+ref <a href="http://blog.golang.org/2011/06/profiling-go-programs.html">
+profiling</a>
+<pre>
+const rows,cols=4,7
+
+m := [rows][cols]byte{}
+// TODO: reduce rows*cols to 1 + rows allocation when byte is large type.
+
+for y,i:=0,0; y&lt;rows; y++ {
+for x:=0; x&lt;cols; x,i = x+1, i+1 {
+m[y][x]= '0' + byte(i)
+}
+}
+// display it
+for y:=0; y&lt;rows; y++ {
+for x:=0; x&lt;cols; x++ {
+fmt.Printf("%c",m[y][x])
+}
+fmt.Print("\n")
+}
+</pre>
+
+
+<h3 id="reserved_keyword_mapping">Reserved Keyword Mapping</h3>
+<table class="codetable" frame="border" summary="Reserved Keyword Mapping">
+<colgroup align="left" width="10%"></colgroup>
+<colgroup align="left" width="90%"></colgroup>
+<tr>
+<th align="left">C/C++</th>
+<th align="left">Go</th>
+</tr>
+<tr>
+<td colspan="2"><hr></td>
+</tr>
+<!--C reserved words -->
+<tr><td>auto</td> <td>X</td></tr>
+<tr><td>break</td> <td>break [Label] to outer loop</td></tr>
+<tr><td>case</td> <td>case can accept multiple values</td></tr>
+<tr><td>char</td> <td>int8/uint8/byte</td></tr>
+<tr><td>const</td> <td>only for define constant variable in global/function</td> </tr>
+<tr><td>continue</td> <td>continue [Label] to outer loop</td></tr>
+<tr><td>default</td> <td>default</td></tr>
+<tr><td valign="top">do</td> <td><a href="go_spec.html#For_statements">for</a>
+<pre>
+for bFirst:=true ; bFirst || expr ; bFirst = false {
+...
+}
+</pre></td></tr>
+<tr><td>double</td> <td>float64</td></tr>
+<tr><td>else</td> <td>else</td></tr>
+<tr><td valign="top">enum</td> <td>
+<pre>
+// use const and/or itoa instead
+type mymask uint8
+const (
+m1 = mymask(1&lt;&lt;iota)
+m2
+m4
+m5 = mymask(5)
+)
+</pre>
+<tr><td>extern</td> <td>all global declaration which name lead with uppercase
+</td></tr>
+<tr><td>float</td> <td>float32</td></tr>
+<tr><td>for</td> <td><a href="go_spec.html#For_statements">for</a></td></tr>
+<tr><td>goto</td> <td>goto</td></tr>
+<tr><td>if</td> <td>if</td></tr>
+<tr><td>int</td> <td><a href="../pkg/builtin#int">int</a> is not alias of int32, use int8,uint16,...
+</td></tr>
+<tr><td>long</td> <td>int32 for 4 bytes, int64 for 8 bytes</td></tr>
+<tr><td>register</td> <td>X</td></tr>
+<tr><td>return</td> <td>could return multiple values</td></tr>
+<tr><td>short</td> <td>int16</td></tr>
+<tr><td>signed</td> <td>uint,uint8,uint16,uint32,uint64</td></tr>
+<tr><td>sizeof</td> <td>unsafe.Sizeof</td></tr>
+<tr><td valign="top">static</td> <td><pre>
+// use closure method to implement static variable
+func f() func() int {
+i := 100
+return func() int { i++ ; return i }
+}
+func main() {
+next := f()
+println(next(), next(), next())
+}
+</pre></td></tr>
+<tr><td>struct</td> <td><a href="go_spec.html#Struct_types">struct</a></td></tr>
+<tr><td valign="top">switch</td> <td><a href="go_spec.html#Switch_statements">sw itch</a>
+accept not only integers.
+<pre>
+switch i { // i=1/2/3 will only produce one line output
+case 1: case 2: println("It is", i)
+case 3: println("It's three")
+}
+// is equal to
+switch i {
+case 1, 2: println("It is", i)
+case 3: println("It's three")
+}
+// the code with same logic as C/C++ code, show two line output for i==1
+switch i {
+case 1: case 2: println("It is", i); fallthrough
+case 3: println("It's three")
+}
+</pre>
+</td></tr>
+<tr><td>typedef</td> <td><a href="go_spec.html#Types">type</a></td></tr>
+<tr><td>union</td> <td>X</td></tr>
+<tr><td>unsigned</td> <td>uint8,uint16,uint32,uint64</td></tr>
+<tr><td>void</td> <td>X</td></tr>
+<tr><td>volatile</td> <td>X</td></tr>
+<tr><td>while</td> <td><a href="go_spec.html#For_statements">for</a></td></tr>
+
+<!--C++ reserved words -->
+<td colspan="2"><hr></td>
+<tr><td>asm</td> <td>try to import C by <a href="../cmd/cgo">cgo</a></td></tr>
+<tr><td>dynamic_cast</td> <td>X</td></tr>
+<tr><td>namespace</td> <td>X</td></tr>
+<tr><td>reinterpret_cast</td> <td>X</td></tr>
+<tr><td>try</td> <td><a href="go_spec.html#Handling_panics">panic</a>
+</td></tr>
+<tr><td>bool</td> <td>bool</td></tr>
+<tr><td>explicit</td> <td>X</td></tr>
+<tr><td>new</td> <td><a href="go_spec.html#Allocation">new/make</a></td></tr>
+<tr><td>static_cast</td> <td>X</td></tr>
+<tr><td>typeid</td> <td>X</td></tr>
+<tr><td>catch</td> <td><a href="go_spec.html#Handling_panics">panic</a>
+<tr><td>false</td> <td>false</td></tr>
+<tr><td>operator</td> <td>X</td></tr>
+<tr><td>template</td> <td>X</td></tr>
+<tr><td>typename</td> <td>X</td></tr>
+<tr><td>class</td> <td><a href="#Interfaces">type + interface</a></td></tr>
+<tr><td>friend</td> <td>X</td></tr>
+<tr><td>private</td> <td>name's first char prefix with lowercase</td></tr>
+<tr><td>this</td> <td>X</td></tr>
+<tr><td>using</td> <td>X</td></tr>
+<tr><td>const_cast</td> <td>X</td></tr>
+<tr><td>inline</td> <td>X</td></tr>
+<tr><td>public</td> <td>name's first char prefix with uppercase</td></tr>
+<tr><td>throw</td> <td>X</td></tr>
+<tr><td>virtual</td> <td>X</td></tr>
+<tr><td>delete</td>
+<td>automatic garbage collection, delete(m,k) for del map item</td></tr>
+<tr><td>mutable</td> <td>X</td></tr>
+<tr><td>protected</td> <td>X</td></tr>
+<tr><td>true</td> <td>true</td></tr>
+<tr><td>wchar_t</td> <td>rune</td></tr>
+
+<!--some predefined identifiers -->
+<td colspan="2"><hr></td>
+<tr><td>cin</td> <td>os.Stdin</td></tr>
+<tr><td>cout</td> <td>os.Stdout</td></tr>
+<tr><td>endl</td> <td>use Println(), xxxln(), or "\n"</td></tr>
+<tr><td>include</td> <td><a href="go_spec.html#Import_declarations">import</a>,
+see also "go help importpath"</td></tr>
+<tr><td>INT_MIN</td> <td>X</td></tr>
+<tr><td>INT_MAX</td> <td>X</td></tr>
+<tr><td>iomanip</td> <td><a href="../pkg/fmt">fmt</a></td></tr>
+<tr><td>iostream</td> <td>
+<a href="../pkg/bufio">bufio</a>,
+<a href="../pkg/fmt">fmt</a>,
+<a href="../pkg/io">io</a>,
+<a href="../pkg/io/ioutil">io/ioutil</a>
+</td></tr>
+<tr><td>main</td> <td><a href="go_spec.html#Packages">package</a>,
+To return error code to OS, use os.Exit() instead of return from main()
+</td></tr>
+<tr><td>MAX_RAND</td> <td>X</td></tr>
+<tr><td>NULL</td> <td>nil</td></tr>
+<tr><td>string</td> <td>
+<a href="go_spec.html#String_types">string</a>,·
+see also <a href="../pkg/strconv">strconv</a>
+</td></tr>
+<tr>
+<td colspan="2"><hr></td>
+</tr>
+</table>
+
+
+<h3 id="other_mapping">Other Mapping</h3>
+
+<table class="codetable" frame="border" summary="Other Mapping">
+<colgroup align="left" width="10%"></colgroup>
+<colgroup align="left" width="90%"></colgroup>
+<tr>
+<th align="left">C/C++</th>
+<th align="left">Go</th>
+</tr>
+<!-- common programing behavior -->
+<tr><td colspan="2"><hr></td></tr>
+<tr><td>argc</td> <td>len(os.Args)</td></tr>
+<tr><td>argv</td> <td>os.Args</td></tr>
+
+<!-- common functions -->
+<tr><td colspan="2"><hr></td></tr>
+<tr><td>atof</td> <td>strconv.parseFloat</td></tr>
+<tr><td>atoi</td> <td>strconv.ParseFloat</td></tr>
+<tr><td>getopt</td> <td><a href="../pkg/flag">flag</a></td></tr>
+<tr><td>itoa</td> <td>strconv.Itoa/FormatInt/FormatUint</td></tr>
+<tr><td valign="top">printf</td> <td>fmt.Print/Printf/Println.
+Go's Print is powerful, it could print any type with String() member.
+For xxxf() function, we can use "go tool vet *.go" to validate % flags
+</td></tr>
+<tr><td>scanf</td> <td>fmt.Scan/Scanf/Scanln</td></tr>
+<tr><td>sscanf</td> <td>fmt.Sscan/Sscanf/Sscanln</td></tr>
+<tr><td>sprintf</td> <td>fmt.Sprint/Sprintf/Sprintln</td></tr>
+
+<!-- C++ STL -->
+<tr><td colspan="2"><hr></td></tr>
+<tr><td>bitset</td> <td>X</td></tr>
+<tr><td>deque</td> <td><a href="../pkg/container/list">container/list</a></td></ tr>
+<tr><td>hashmap</td> <td><a href="go_spec.html#Map_types">map</a></td></tr>
+<tr><td>list</td> <td><a href="../pkg/container/list">container/list</a></td></t r>
+<tr><td valign="top">map</td> <td><a href="go_spec.html#Map_types">map</a>
+like C++'s hashmap, it is unordered.
+<pre>
+var m = map[string]int{ "Mon":1, "Tue":2 }
+for k,v := range m { fmt.Println("k=",k,"v=",v"} // display
+// NOTE: iterate order is dynamic, don't treat it is consistent
+m["Wed"] = 2 // insert
+m["Wed"] = 3 // update
+delete(m,"Wed") // delete
+var m2 = make(map[string]string, 1e4) // pre-allocate initial size
+</pre>
+</tr>
+<tr><td>multiset</td> <td>X</td></tr>
+<tr><td>multimap</td> <td>X</td></tr>
+<tr><td valign="top">queue</td> <td>
+In general case, use <a href="go_spec.html#Slices">slice</a> instead.
+Or, use <a href="../pkg/container/list">container/list</a>
+if don't like the slice memory allocation.
+Code come from <a href="http://code.google.com/p/go-wiki/wiki/SliceTricks">
+SliceTricks</a><pre>
+var q = []string
+q = append(q, "Jan") // push
+q = append(q, "Feb") // push
+v, q = q[len(q)-1], q[:len(q)-1] // pop, use trick of assign multiple value
+</pre></td></tr>
+<tr><td>priority_queue</td> <td>X</td></tr>
+<tr><td>set</td> <td>X</td></tr>
+<tr><td>stack</td> <td><a href="../pkg/container/list">container/list</a></td></ tr>
+<tr><td valign="top">vector</td> <td>
+use <a href="go_spec.html#Slices">slice</a> instead.
+code come from <a href="http://code.google.com/p/go-wiki/wiki/SliceTricks">
+SliceTricks</a><pre>
+var v = []int
+v = append(v, 3) // append an element
+var v2 = []int{5,6}
+for i,v := range(v) { fmt.Println("index=", i, "value=", v)} // display
+v = append(v, v2...) // append another vector
+v = append(a[:1], append([]int{4}, a[1:]...)...) // insert 4 before v[1]
+v[3]=99 // update
+v = append(a[:1], a[2:]...) // delete element v[1]
+</pre></td></tr>
+
+<tr> <td colspan="2"><hr></td> </tr>
+</table>