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go spec: "delete" built-in function

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https://golang.org/cl/5272045
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Robert Griesemer 2011-10-17 12:53:10 -07:00
parent b0c674b65d
commit 3e0c0a8add
1 changed files with 25 additions and 18 deletions
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43
doc/go_spec.html
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@ -1159,9 +1159,10 @@ map [string] interface {}
The number of map elements is called its length. The number of map elements is called its length.
For a map <code>m</code>, it can be discovered using the For a map <code>m</code>, it can be discovered using the
built-in function <a href="#Length_and_capacity"><code>len(m)</code></a> built-in function <a href="#Length_and_capacity"><code>len(m)</code></a>
and may change during execution. Elements may be added and removed and may change during execution. Elements may be added during execution
during execution using special forms of <a href="#Assignments">assignment</a>; using <a href="#Assignments">assignments</a> and retrieved with
and they may be accessed with <a href="#Indexes">index</a> expressions. <a href="#Indexes">index</a> expressions; they may be removed with the
<a href="#Deletion_of_map_elements"><code>delete</code></a> built-in function.
</p> </p>
<p> <p>
A new, empty map value is made using the built-in A new, empty map value is made using the built-in
@ -2431,21 +2432,6 @@ where the result of the index expression is a pair of values with types
<code>a[x]</code> as in the single-result form. <code>a[x]</code> as in the single-result form.
</p> </p>
<p>
Similarly, if an assignment to a map element has the special form
</p>
<pre>
a[x] = v, ok
</pre>
<p>
and boolean <code>ok</code> has the value <code>false</code>,
the entry for key <code>x</code> is deleted from the map; if
<code>ok</code> is <code>true</code>, the construct acts like
a regular assignment to an element of the map.
</p>
<p> <p>
Assigning to an element of a <code>nil</code> map causes a Assigning to an element of a <code>nil</code> map causes a
<a href="#Run_time_panics">run-time panic</a>. <a href="#Run_time_panics">run-time panic</a>.
@ -4738,6 +4724,27 @@ n2 := copy(s, s[2:]) // n2 == 4, s == []int{2, 3, 4, 5, 4, 5}
n3 := copy(b, "Hello, World!") // n3 == 5, b == []byte("Hello") n3 := copy(b, "Hello, World!") // n3 == 5, b == []byte("Hello")
</pre> </pre>
<h3 id="Deletion_of_map_elements">Deletion of map elements</h3>
<p>
The built-in function <code>delete</code> removes the element with key
<code>k</code> from a <a href="#Map_types">map</a> <code>m</code>. The
type of <code>k</code> must be <a href="#Assignability">assignable</a>
to the key type of <code>m</code>.
</p>
<pre class="grammar">
delete(m, k) // remove element m[k] from map m
</pre>
<p>
If the element <code>m[k]</code> does not exist, <code>delete</code> is
a no-op. Calling <code>delete</code> with a nil map causes a
<a href="#Run_time_panics">run-time panic</a>.
</p>
<h3 id="Complex_numbers">Assembling and disassembling complex numbers</h3> <h3 id="Complex_numbers">Assembling and disassembling complex numbers</h3>
<p> <p>