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docs: remove some prose-unworthy empty parentheses.

In our evolving style, prose should name a function "f" not "f()".

R=gri, rsc
CC=golang-dev
https://golang.org/cl/4550075
This commit is contained in:
Rob Pike 2011-05-25 06:44:09 +10:00
parent bdbe0decc6
commit 46f482a2fc
4 changed files with 57 additions and 55 deletions

View File

@ -935,13 +935,14 @@ example of its possibilities.
<h2 id="data">Data</h2>
<h3 id="allocation_new">Allocation with <code>new()</code></h3>
<h3 id="allocation_new">Allocation with <code>new</code></h3>
<p>
Go has two allocation primitives, <code>new()</code> and <code>make()</code>.
Go has two allocation primitives, the built-in functions
<code>new</code> and <code>make</code>.
They do different things and apply to different types, which can be confusing,
but the rules are simple.
Let's talk about <code>new()</code> first.
Let's talk about <code>new</code> first.
It's a built-in function essentially the same as its namesakes
in other languages: <code>new(T)</code> allocates zeroed storage for a new item of type
<code>T</code> and returns its address, a value of type <code>*T</code>.
@ -950,9 +951,9 @@ In Go terminology, it returns a pointer to a newly allocated zero value of type
</p>
<p>
Since the memory returned by <code>new()</code> is zeroed, it's helpful to arrange that the
Since the memory returned by <code>new</code> is zeroed, it's helpful to arrange that the
zeroed object can be used without further initialization. This means a user of
the data structure can create one with <code>new()</code> and get right to
the data structure can create one with <code>new</code> and get right to
work.
For example, the documentation for <code>bytes.Buffer</code> states that
"the zero value for <code>Buffer</code> is an empty buffer ready to use."
@ -1065,7 +1066,7 @@ s := []string {Enone: "no error", Eio: "Eio", Einval: "invalid argument"}
m := map[int]string{Enone: "no error", Eio: "Eio", Einval: "invalid argument"}
</pre>
<h3 id="allocation_make">Allocation with <code>make()</code></h3>
<h3 id="allocation_make">Allocation with <code>make</code></h3>
<p>
Back to allocation.
@ -1099,8 +1100,8 @@ In contrast, <code>new([]int)</code> returns a pointer to a newly allocated, zer
structure, that is, a pointer to a <code>nil</code> slice value.
<p>
These examples illustrate the difference between <code>new()</code> and
<code>make()</code>.
These examples illustrate the difference between <code>new</code> and
<code>make</code>.
</p>
<pre>
@ -1116,9 +1117,9 @@ v := make([]int, 100)
</pre>
<p>
Remember that <code>make()</code> applies only to maps, slices and channels
Remember that <code>make</code> applies only to maps, slices and channels
and does not return a pointer.
To obtain an explicit pointer allocate with <code>new()</code>.
To obtain an explicit pointer allocate with <code>new</code>.
</p>
<h3 id="arrays">Arrays</h3>
@ -1473,7 +1474,7 @@ map[string] int
</pre>
<p>
If you want to control the default format for a custom type, all that's required is to define
a method <code>String() string</code> on the type.
a method with the signature <code>String() string</code> on the type.
For our simple type <code>T</code>, that might look like this.
</p>
<pre>
@ -1495,7 +1496,7 @@ that's more efficient and idiomatic for struct types.
See the section below on <a href="#pointers_vs_values">pointers vs. value receivers</a> for more information.)
</p>
<p>
Our <code>String()</code> method is able to call <code>Sprintf</code> because the
Our <code>String</code> method is able to call <code>Sprintf</code> because the
print routines are fully reentrant and can be used recursively.
We can even go one step further and pass a print routine's arguments directly to another such routine.
The signature of <code>Printf</code> uses the type <code>...interface{}</code>
@ -1683,19 +1684,20 @@ var (
<h3 id="init">The init function</h3>
<p>
Finally, each source file can define its own <code>init()</code> function to
set up whatever state is required. The only restriction is that, although
Finally, each source file can define its own niladic <code>init</code> function to
set up whatever state is required. (Actually each file can have multiple
<code>init</code> functions.) The only restriction is that, although
goroutines can be launched during initialization, they will not begin
execution until it completes; initialization always runs as a single thread
of execution.
And finally means finally: <code>init()</code> is called after all the
And finally means finally: <code>init</code> is called after all the
variable declarations in the package have evaluated their initializers,
and those are evaluated only after all the imported packages have been
initialized.
</p>
<p>
Besides initializations that cannot be expressed as declarations,
a common use of <code>init()</code> functions is to verify or repair
a common use of <code>init</code> functions is to verify or repair
correctness of the program state before real execution begins.
</p>
@ -1899,7 +1901,7 @@ on every instance of a common method.
In such cases, the constructor should return an interface value
rather than the implementing type.
As an example, in the hash libraries
both <code>crc32.NewIEEE()</code> and <code>adler32.New()</code>
both <code>crc32.NewIEEE</code> and <code>adler32.New</code>
return the interface type <code>hash.Hash32</code>.
Substituting the CRC-32 algorithm for Adler-32 in a Go program
requires only changing the constructor call;

View File

@ -1,5 +1,5 @@
<!-- title The Go Programming Language Specification -->
<!-- subtitle Version of May 23, 2011 -->
<!-- subtitle Version of May 24, 2011 -->
<!--
TODO
@ -821,7 +821,7 @@ make([]T, length, capacity)
</pre>
<p>
The <code>make()</code> call allocates a new, hidden array to which the returned
A call to <code>make</code> allocates a new, hidden array to which the returned
slice value refers. That is, executing
</p>
@ -4931,7 +4931,7 @@ func main() {
<h3 id="The_zero_value">The zero value</h3>
<p>
When memory is allocated to store a value, either through a declaration
or <code>make()</code> or <code>new()</code> call,
or a call of <code>make</code> or <code>new</code>,
and no explicit initialization is provided, the memory is
given a default initialization. Each element of such a value is
set to the <i>zero value</i> for its type: <code>false</code> for booleans,
@ -4989,7 +4989,7 @@ func init()
<p>
defined in its source.
A package may contain multiple
<code>init()</code> functions, even
<code>init</code> functions, even
within a single source file; they execute
in unspecified order.
</p>
@ -5019,8 +5019,8 @@ program is complete. Therefore, all initialization code is run in a single
goroutine.
</p>
<p>
An <code>init()</code> function cannot be referred to from anywhere
in a program. In particular, <code>init()</code> cannot be called explicitly,
An <code>init</code> function cannot be referred to from anywhere
in a program. In particular, <code>init</code> cannot be called explicitly,
nor can a pointer to <code>init</code> be assigned to a function variable.
</p>
<p>

View File

@ -341,7 +341,7 @@ Using slices one can write this function (from <code>sum.go</code>):
15 }
</pre>
<p>
Note how the return type (<code>int</code>) is defined for <code>sum()</code> by stating it
Note how the return type (<code>int</code>) is defined for <code>sum</code> by stating it
after the parameter list.
<p>
To call the function, we slice the array. This intricate call (we'll show
@ -373,7 +373,7 @@ There are also maps, which you can initialize like this:
m := map[string]int{"one":1 , "two":2}
</pre>
<p>
The built-in function <code>len()</code>, which returns number of elements,
The built-in function <code>len</code>, which returns number of elements,
makes its first appearance in <code>sum</code>. It works on strings, arrays,
slices, maps, and channels.
<p>
@ -401,7 +401,7 @@ for more examples of its use.
Most types in Go are values. If you have an <code>int</code> or a <code>struct</code>
or an array, assignment
copies the contents of the object.
To allocate a new variable, use <code>new()</code>, which
To allocate a new variable, use the built-in function <code>new</code>, which
returns a pointer to the allocated storage.
<p>
<pre>
@ -418,7 +418,7 @@ or the more idiomatic
Some types&mdash;maps, slices, and channels (see below)&mdash;have reference semantics.
If you're holding a slice or a map and you modify its contents, other variables
referencing the same underlying data will see the modification. For these three
types you want to use the built-in function <code>make()</code>:
types you want to use the built-in function <code>make</code>:
<p>
<pre>
m := make(map[string]int)
@ -432,11 +432,11 @@ If you just declare the map, as in
</pre>
<p>
it creates a <code>nil</code> reference that cannot hold anything. To use the map,
you must first initialize the reference using <code>make()</code> or by assignment from an
you must first initialize the reference using <code>make</code> or by assignment from an
existing map.
<p>
Note that <code>new(T)</code> returns type <code>*T</code> while <code>make(T)</code> returns type
<code>T</code>. If you (mistakenly) allocate a reference object with <code>new()</code>,
<code>T</code>. If you (mistakenly) allocate a reference object with <code>new</code> rather than <code>make</code>,
you receive a pointer to a nil reference, equivalent to
declaring an uninitialized variable and taking its address.
<p>
@ -767,7 +767,7 @@ Building on the <code>file</code> package, here's a simple version of the Unix u
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
initialization statement. The <code>switch</code> on line 18 uses one to create variables
<code>nr</code> and <code>er</code> to hold the return values from <code>f.Read()</code>. (The <code>if</code> on line 25
<code>nr</code> and <code>er</code> to hold the return values from the call to <code>f.Read</code>. (The <code>if</code> on line 25
has the same idea.) The <code>switch</code> statement is general: it evaluates the cases
from top to bottom looking for the first case that matches the value; the
case expressions don't need to be constants or even integers, as long as
@ -779,14 +779,14 @@ in a <code>for</code> statement, a missing value means <code>true</code>. In fa
is a form of <code>if-else</code> chain. While we're here, it should be mentioned that in
<code>switch</code> statements each <code>case</code> has an implicit <code>break</code>.
<p>
Line 25 calls <code>Write()</code> by slicing the incoming buffer, which is itself a slice.
Line 25 calls <code>Write</code> by slicing the incoming buffer, which is itself a slice.
Slices provide the standard Go way to handle I/O buffers.
<p>
Now let's make a variant of <code>cat</code> that optionally does <code>rot13</code> on its input.
It's easy to do by just processing the bytes, but instead we will exploit
Go's notion of an <i>interface</i>.
<p>
The <code>cat()</code> subroutine uses only two methods of <code>f</code>: <code>Read()</code> and <code>String()</code>,
The <code>cat</code> subroutine uses only two methods of <code>f</code>: <code>Read</code> and <code>String</code>,
so let's start by defining an interface that has exactly those two methods.
Here is code from <code>progs/cat_rot13.go</code>:
<p>
@ -838,7 +838,7 @@ To use the new feature, we define a flag:
14 var rot13Flag = flag.Bool(&quot;rot13&quot;, false, &quot;rot13 the input&quot;)
</pre>
<p>
and use it from within a mostly unchanged <code>cat()</code> function:
and use it from within a mostly unchanged <code>cat</code> function:
<p>
<pre> <!-- progs/cat_rot13.go /func.cat/ /^}/ -->
52 func cat(r reader) {
@ -866,7 +866,7 @@ and use it from within a mostly unchanged <code>cat()</code> function:
74 }
</pre>
<p>
(We could also do the wrapping in <code>main</code> and leave <code>cat()</code> mostly alone, except
(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.)
Lines 56 through 58 set it all up: If the <code>rot13</code> flag is true, wrap the <code>reader</code>
we received into a <code>rotate13</code> and proceed. Note that the interface variables
@ -1055,7 +1055,7 @@ to that of the <code>Printf</code> call above.
</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
just give it a <code>String</code> method that returns a string. The print
routines will examine the value to inquire whether it implements
the method and if so, use it rather than some other formatting.
Here's a simple example.
@ -1076,14 +1076,14 @@ Here's a simple example.
21 }
</pre>
<p>
Since <code>*testType</code> has a <code>String()</code> method, the
Since <code>*testType</code> has a <code>String</code> method, the
default formatter for that type will use it and produce the output
<p>
<pre>
77 Sunset Strip
</pre>
<p>
Observe that the <code>String()</code> method calls <code>Sprint</code> (the obvious Go
Observe that the <code>String</code> method calls <code>Sprint</code> (the obvious Go
variant that returns a string) to do its formatting; special formatters
can use the <code>fmt</code> library recursively.
<p>
@ -1096,7 +1096,7 @@ and such, but that's getting a little off the main thread so we'll leave it
as an exploration exercise.
<p>
You might ask, though, how <code>Printf</code> can tell whether a type implements
the <code>String()</code> method. Actually what it does is ask if the value can
the <code>String</code> method. Actually what it does is ask if the value can
be converted to an interface variable that implements the method.
Schematically, given a value <code>v</code>, it does this:
<p>
@ -1141,7 +1141,7 @@ interface type defined in the <code>io</code> library:
<p>
(This interface is another conventional name, this time for <code>Write</code>; there are also
<code>io.Reader</code>, <code>io.ReadWriter</code>, and so on.)
Thus you can call <code>Fprintf</code> on any type that implements a standard <code>Write()</code>
Thus you can call <code>Fprintf</code> on any type that implements a standard <code>Write</code>
method, not just files but also network channels, buffers, whatever
you want.
<p>

View File

@ -272,7 +272,7 @@ Using slices one can write this function (from "sum.go"):
--PROG progs/sum.go /sum/ /^}/
Note how the return type ("int") is defined for "sum()" by stating it
Note how the return type ("int") is defined for "sum" by stating it
after the parameter list.
To call the function, we slice the array. This intricate call (we'll show
@ -296,7 +296,7 @@ There are also maps, which you can initialize like this:
m := map[string]int{"one":1 , "two":2}
The built-in function "len()", which returns number of elements,
The built-in function "len", which returns number of elements,
makes its first appearance in "sum". It works on strings, arrays,
slices, maps, and channels.
@ -321,7 +321,7 @@ An Interlude about Allocation
Most types in Go are values. If you have an "int" or a "struct"
or an array, assignment
copies the contents of the object.
To allocate a new variable, use "new()", which
To allocate a new variable, use the built-in function "new", which
returns a pointer to the allocated storage.
type T struct { a, b int }
@ -334,7 +334,7 @@ or the more idiomatic
Some types&mdash;maps, slices, and channels (see below)&mdash;have reference semantics.
If you're holding a slice or a map and you modify its contents, other variables
referencing the same underlying data will see the modification. For these three
types you want to use the built-in function "make()":
types you want to use the built-in function "make":
m := make(map[string]int)
@ -344,11 +344,11 @@ If you just declare the map, as in
var m map[string]int
it creates a "nil" reference that cannot hold anything. To use the map,
you must first initialize the reference using "make()" or by assignment from an
you must first initialize the reference using "make" or by assignment from an
existing map.
Note that "new(T)" returns type "*T" while "make(T)" returns type
"T". If you (mistakenly) allocate a reference object with "new()",
"T". If you (mistakenly) allocate a reference object with "new" rather than "make",
you receive a pointer to a nil reference, equivalent to
declaring an uninitialized variable and taking its address.
@ -526,7 +526,7 @@ Building on the "file" package, here's a simple version of the Unix utility "cat
By now this should be easy to follow, but the "switch" statement introduces some
new features. Like a "for" loop, an "if" or "switch" can include an
initialization statement. The "switch" on line 18 uses one to create variables
"nr" and "er" to hold the return values from "f.Read()". (The "if" on line 25
"nr" and "er" to hold the return values from the call to "f.Read". (The "if" on line 25
has the same idea.) The "switch" statement is general: it evaluates the cases
from top to bottom looking for the first case that matches the value; the
case expressions don't need to be constants or even integers, as long as
@ -538,14 +538,14 @@ in a "for" statement, a missing value means "true". In fact, such a "switch"
is a form of "if-else" chain. While we're here, it should be mentioned that in
"switch" statements each "case" has an implicit "break".
Line 25 calls "Write()" by slicing the incoming buffer, which is itself a slice.
Line 25 calls "Write" by slicing the incoming buffer, which is itself a slice.
Slices provide the standard Go way to handle I/O buffers.
Now let's make a variant of "cat" that optionally does "rot13" on its input.
It's easy to do by just processing the bytes, but instead we will exploit
Go's notion of an <i>interface</i>.
The "cat()" subroutine uses only two methods of "f": "Read()" and "String()",
The "cat" subroutine uses only two methods of "f": "Read" and "String",
so let's start by defining an interface that has exactly those two methods.
Here is code from "progs/cat_rot13.go":
@ -569,11 +569,11 @@ To use the new feature, we define a flag:
--PROG progs/cat_rot13.go /rot13Flag/
and use it from within a mostly unchanged "cat()" function:
and use it from within a mostly unchanged "cat" function:
--PROG progs/cat_rot13.go /func.cat/ /^}/
(We could also do the wrapping in "main" and leave "cat()" mostly alone, except
(We could also do the wrapping in "main" and leave "cat" mostly alone, except
for changing the type of the argument; consider that an exercise.)
Lines 56 through 58 set it all up: If the "rot13" flag is true, wrap the "reader"
we received into a "rotate13" and proceed. Note that the interface variables
@ -701,19 +701,19 @@ to that of the "Printf" call above.
--PROG progs/print.go 'NR==21' 'NR==22'
If you have your own type you'd like "Printf" or "Print" to format,
just give it a "String()" method that returns a string. The print
just give it a "String" method that returns a string. The print
routines will examine the value to inquire whether it implements
the method and if so, use it rather than some other formatting.
Here's a simple example.
--PROG progs/print_string.go 'NR==9' END
Since "*testType" has a "String()" method, the
Since "*testType" has a "String" method, the
default formatter for that type will use it and produce the output
77 Sunset Strip
Observe that the "String()" method calls "Sprint" (the obvious Go
Observe that the "String" method calls "Sprint" (the obvious Go
variant that returns a string) to do its formatting; special formatters
can use the "fmt" library recursively.
@ -726,7 +726,7 @@ and such, but that's getting a little off the main thread so we'll leave it
as an exploration exercise.
You might ask, though, how "Printf" can tell whether a type implements
the "String()" method. Actually what it does is ask if the value can
the "String" method. Actually what it does is ask if the value can
be converted to an interface variable that implements the method.
Schematically, given a value "v", it does this:
@ -765,7 +765,7 @@ interface type defined in the "io" library:
(This interface is another conventional name, this time for "Write"; there are also
"io.Reader", "io.ReadWriter", and so on.)
Thus you can call "Fprintf" on any type that implements a standard "Write()"
Thus you can call "Fprintf" on any type that implements a standard "Write"
method, not just files but also network channels, buffers, whatever
you want.