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Return type can now be omitted on adaptable function objects

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[SVN r11401]
This commit is contained in:
Peter Dimov
2001-10-18 15:05:57 +00:00
parent b9bb33048f
commit c61d480cb6
3 changed files with 230 additions and 54 deletions
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bind.html
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@@ -17,7 +17,7 @@
<td align="center">
<table border="0">
<tr><td nowrap><h1>bind.hpp</h1></td></tr>
<tr><td align="right" nowrap><small>&nbsp;1.01.0001 (2001-09-02)</small></td></tr>
<tr><td align="right" nowrap><small>&nbsp;1.02.0001 (2001-10-18)</small></td></tr>
</table>
</td>
</tr>
@@ -108,6 +108,14 @@ bind(g, _3, _3, _3)(x, y, z); // g(z, z, z)
bind(g, _1, _1, _1)(x, y, z); // g(x, x, x)
</pre>
<p>
Note that, in the last example, the function object produced by
<tt>bind(g, _1, _1, _1)</tt> does not contain references to any arguments
beyond the first, but it can still be used with more than one argument.
Any extra arguments are silently ignored, just like the first and the second
argument are ignored in the third example.
</p>
<p>
The arguments that <b>bind</b> takes are copied and held internally by
the returned function object. For example, in the following code:
@@ -135,10 +143,10 @@ bind(f, ref(i), _1);
<h3>Using bind with function objects</h3>
<p>
Any function object can be passed as a first argument to <b>bind</b>, but the
syntax is a bit different. The return type of the generated function object's
<b>bind</b> is not limited to functions; it accepts arbitrary function objects.
In the general case, the return type of the generated function object's
<b>operator()</b> has to be specified explicitly (without a <b>typeof</b>
operator the return type cannot be inferred in the general case):
operator the return type cannot be inferred):
</p>
<pre>
@@ -156,11 +164,18 @@ bind&lt;int&gt;(f, _1, _1)(x); // f(x, x), i.e. zero
</pre>
<p>
[Note: when, hopefully,
<a href="http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/cwg_active.html#226">
function template default arguments</a> become part of C++,
<b>bind</b> will no longer require the explicit specification of the return type
when the function object defines <b>result_type</b>.]
When the function object exposes a nested type named <b>result_type</b>,
the explicit return type can be omitted:
</p>
<pre>
int x = 8;
bind(std::less&lt;int&gt;, _1, 9)(x); // x < 9
</pre>
<p>
[Note: the ability to omit the return type is not available on all compilers.]
</p>
<h3>Using bind with member function pointers</h3>
@@ -392,12 +407,16 @@ namespace boost
template&lt;class R, class F&gt; <i>implementation-defined-1</i> <a href="#bind_1">bind</a>(F f);
template&lt;class F&gt; <i>implementation-defined-1-1</i> <a href="#bind_1_1">bind</a>(F f);
template&lt;class R&gt; <i>implementation-defined-2</i> <a href="#bind_2">bind</a>(R (*f) ());
// one argument
template&lt;class R, class F, class A1&gt; <i>implementation-defined-3</i> <a href="#bind_3">bind</a>(F f, A1 a1);
template&lt;class F, class A1&gt; <i>implementation-defined-3-1</i> <a href="#bind_3_1">bind</a>(F f, A1 a1);
template&lt;class R, class B1, class A1&gt; <i>implementation-defined-4</i> <a href="#bind_4">bind</a>(R (*f) (B1), A1 a1);
template&lt;class R, class T, class A1&gt; <i>implementation-defined-5</i> <a href="#bind_5">bind</a>(R (T::*f) (), A1 a1);
@@ -408,6 +427,8 @@ template&lt;class R, class T, class A1&gt; <i>implementation-defined-6</i> <a hr
template&lt;class R, class F, class A1, class A2&gt; <i>implementation-defined-7</i> <a href="#bind_7">bind</a>(F f, A1 a1, A2 a2);
template&lt;class F, class A1, class A2&gt; <i>implementation-defined-7-1</i> <a href="#bind_7_1">bind</a>(F f, A1 a1, A2 a2);
template&lt;class R, class B1, class B2, class A1, class A2&gt; <i>implementation-defined-8</i> <a href="#bind_8">bind</a>(R (*f) (B1, B2), A1 a1, A2 a2);
template&lt;class R, class T, class B1, class A1, class A2&gt; <i>implementation-defined-9</i> <a href="#bind_9">bind</a>(R (T::*f) (B1), A1 a1, A2 a2);
@@ -474,6 +495,12 @@ implicitly converted to <b>R</b>.
<b>Throws:</b> Nothing unless the copy constructor of <b>F</b> throws an exception.
</p>
<h4><a name="bind_1_1">template&lt;class F&gt; <i>implementation-defined-1-1</i> bind(F f)</a></h4>
<p>
<b>Effects:</b> equivalent to <tt>bind&lt;typename F::result_type, F&gt;(f);</tt>
</p>
<h4><a name="bind_2">template&lt;class R&gt; <i>implementation-defined-2</i> bind(R (*f) ())</a></h4>
<p>
@@ -496,6 +523,12 @@ implicitly converted to <b>R</b>.
<b>Throws:</b> Nothing unless the copy constructors of <b>F</b> and <b>A1</b> throw an exception.
</p>
<h4><a name="bind_3_1">template&lt;class F, class A1&gt; <i>implementation-defined-3-1</i> bind(F f, A1 a1)</a></h4>
<p>
<b>Effects:</b> equivalent to <tt>bind&lt;typename F::result_type, F, A1&gt;(f, a1);</tt>
</p>
<h4><a name="bind_4">template&lt;class R, class B1, class A1&gt; <i>implementation-defined-4</i> bind(R (*f) (B1), A1 a1)</a></h4>
<p>
@@ -531,6 +564,12 @@ implicitly converted to <b>R</b>.
<b>Throws:</b> Nothing unless the copy constructors of <b>F</b>, <b>A1</b> and <b>A2</b> throw an exception.
</p>
<h4><a name="bind_7_1">template&lt;class F, class A1, class A2&gt; <i>implementation-defined-7-1</i> bind(F f, A1 a1, A2 a2)</a></h4>
<p>
<b>Effects:</b> equivalent to <tt>bind&lt;typename F::result_type, F, A1, A2&gt;(f, a1, a2);</tt>
</p>
<h4><a name="bind_8">template&lt;class R, class B1, class B2, class A1, class A2&gt; <i>implementation-defined-8</i> bind(R (*f) (B1, B2), A1 a1, A2 a2)</a></h4>
<p>
@@ -693,6 +732,11 @@ was Darin Adler.
The precise semantics of <b>bind</b> were refined in discussions with Jaakko J&auml;rvi.
</p>
<p>
Dave Abrahams fixed a MSVC-specific conflict between <b>bind</b> and the
<a href="../utility\iterator_adaptors.htm">iterator adaptors library</a>.
</p>
<p><br><br><br><small>Copyright &copy; 2001 by Peter Dimov and Multi Media
Ltd. Permission to copy, use, modify, sell and distribute this document is
granted provided this copyright notice appears in all copies. This document