📄 subtractive_rng.html

📁 指导程序员合理、高效的进行标准模板库编程。
💻 HTML
字号:
<HTML>
<HEAD>
   <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
   <META NAME="Author" CONTENT="Zafir Anjum">
   <TITLE>MFC Programmer's SourceBook : STL Programmer's Guide</TITLE>
    <META name="description" 
     content="A freely available implementation 
     of the C++ Standard Template Library, including 
     hypertext documentation.">
	<META name="keywords" 
	content="generic programming, STL, standard template library">
</HEAD>

<SCRIPT LANGUAGE="JavaScript"><!--
var adcategory = "cpp";
// -->
</SCRIPT>
<body background="../../fancyhome/back.gif" bgcolor="#FFFFFF" >
<SCRIPT LANGUAGE="JavaScript"><!--
var nfrm = location.href.indexOf("_nfrm_");
var validframes = (top.frames.length > 0 && top.frames['ad'] && top.frames['logo'] );
var random = Math.random();

if( !validframes && nfrm == -1 )
{
	var dclkPage = "www.codeguru.com/";
	if( self.adcategory )
		dclkPage += adcategory;
	else
		dclkPage += "mfc";
	document.write('<nolayer><center>');
	document.write('<iframe src="http://ad.doubleclick.net/adi/' + dclkPage + ';ord='
	 + random + '" width=470 height=62 marginwidth=0 marginheight=0 hspace=0 vspace=0 '
	 + 'frameborder=0 scrolling=no bordercolor="#000000">');
	document.write('<a href="http://ad.doubleclick.net/jump/' + dclkPage + ';ord='
	 + random + '">');
	document.write('<img src="http://ad.doubleclick.net/ad/' + dclkPage + ';ord='
	 + random + '" height=60 width=468>' + '</a>');
	document.write('</iframe>');
	document.write('</center></nolayer>');
	document.write('<layer  src="http://ad.doubleclick.net/adl/' + dclkPage + 
	 ';ord=' + random + '"></layer>');
	document.write('<ilayer visibility=hide width=468 height=83></ilayer>');
}


//		top.location = "/show.cgi?" + adcategory + "=" + location.pathname;


// -->
</SCRIPT>
<noscript>
<p align="center">
<a href="http://ad.doubleclick.net/jump/www.codeguru.com/cpp;ord=Nupbz9FCY34AAHkzk98">
<img src="http://ad.doubleclick.net/ad/www.codeguru.com/cpp;ord=Nupbz9FCY34AAHkzk98"></a>
</p>
</noscript>





<BR Clear>
<H1>subtractive_rng</H1>

<Table CellPadding=0 CellSpacing=0 width=100%>
<TR>
<TD Align=left><Img src = "functors.gif" Alt=""   WIDTH = "194"  HEIGHT = "38" ></TD>
<TD Align=right><Img src = "type.gif" Alt=""   WIDTH = "194"  HEIGHT = "39" ></TD>
</TR>
<TR>
<TD Align=left VAlign=top><b>Category</b>: functors</TD>
<TD Align=right VAlign=top><b>Component type</b>: type</TD>
</TR>
</Table>

<h3>Description</h3>
<tt>Subtractive_rng</tt> is a <A href="RandomNumberGenerator.html">Random Number Generator</A> based on the
subtractive method <A href="#1">[1]</A>.  It is a <A href="UnaryFunction.html">Unary Function</A>: it takes
a single argument <tt>N</tt>, an <tt>unsigned int</tt>, and returns an 
<tt>unsigned int</tt> that is less than <tt>N</tt>.  Successive calls to
the same <tt>subtractive_rng</tt> object <A href="#2">[2]</A> yield a pseudo-random
sequence.
<h3>Example</h3>
<pre>
int main()
{
  subtractive_rng R;
  for (int i = 0; i &lt; 20; ++i)
    cout &lt;&lt; R(5) &lt;&lt; ' ';
  cout &lt;&lt; endl;
}
// The output is   3 2 3 2 4 3 1 1 2 2 0 3 4 4 4 4 2 1 0 0 
</pre>
<h3>Definition</h3>
Defined in <A href="function.h">function.h</A>
<h3>Template parameters</h3>
None.
<h3>Model of</h3>
<A href="RandomNumberGenerator.html">Random Number Generator</A>, <A href="AdaptableUnaryFunction.html" tppabs="http://www.sgi.com/Technology/STL/AdaptableUnaryFunction.shtml">Adaptable Unary Function</A>
<h3>Type requirements</h3>
None.
<h3>Public base classes</h3>
<tt><A href="unary_function.html">unary_function</A>&lt;unsigned int, unsigned int&gt;</tt>
<h3>Members</h3>
<Table border>
<TR>
<TH>
Parameter
</TH>
<TH>
Description
</TH>
<TH>
Default
</TH>
</TR>
<TR>
<TD VAlign=top>
<tt>argument_type</tt>
</TD>
<TD VAlign=top>
 <A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A>
</TD>
<TD VAlign=top>
The type of a <tt>subtractive_rng</tt>'s argument: <tt>unsigned int</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>result_type</tt>
</TD>
<TD VAlign=top>
 <A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A>
</TD>
<TD VAlign=top>
The type of the result: <tt>unsigned int</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>subtractive_rng(unsigned int seed)</tt>
</TD>
<TD VAlign=top>
<tt>subtractive_rng</tt>
</TD>
<TD VAlign=top>
See below.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>subtractive_rng()</tt>
</TD>
<TD VAlign=top>
<tt>subtractive_rng</tt>
</TD>
<TD VAlign=top>
See below.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>unsigned int operator()(unsigned int N)</tt>
</TD>
<TD VAlign=top>
 <A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A>
</TD>
<TD VAlign=top>
Function call.  Returns a pseudo-random number in the range
   <tt>[0, N)</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>void initialize(unsigned int seed)</tt>
</TD>
<TD VAlign=top>
<tt>subtractive_rng</tt>
</TD>
<TD VAlign=top>
See below.
</TD>
</tr>
</table>
<h3>New members</h3>
These members are not defined in the 
<A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A>
requirements, but are specific to 
<tt>subtractive_rng</tt>.
<Table border>
<TR>
<TH>
Member
</TH>
<TH>
Description
</TH>
</TR>
<TR>
<TD VAlign=top>
<tt>subtractive_rng(unsigned int seed)</tt>
</TD>
<TD VAlign=top>
The constructor.  Creates a <tt>subtractive_rng</tt> whose internal state
   is initialized using <tt>seed</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>subtractive_rng()</tt>
</TD>
<TD VAlign=top>
The default constructor.  Creates a <tt>subtractive_rng</tt> initialized
   using a default value.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>void initialize(unsigned int seed)</tt>
</TD>
<TD VAlign=top>
Re-initializes the internal state of the <tt>subtractive_rng</tt>, using
   the value <tt>seed</tt>.
</TD>
</tr>
</table>
<h3>Notes</h3>
<P><A name="1">[1]</A>
See section 3.6 of Knuth for an implementation of the subtractive
method in FORTRAN.  Section 3.2.2 of Knuth analyzes this class of
algorithms.
(D. E. Knuth, <i>The Art of Computer
Programming.  Volume 2: Seminumerical Algorithms</i>, second edition.  
Addison-Wesley, 1981.)
<P><A name="2">[2]</A>
Note that the sequence produced by a <tt>subtractive_rng</tt> is
completely deterministic, and that the sequences produced by two
different <tt>subtractive_rng</tt> objects are independent of each other.
That is: if <tt>R1</tt> is a <tt>subtractive_rng</tt>, then the values returned when
<tt>R1</tt> is called depend only on <tt>R1</tt>'s seed and on the number of times
that <tt>R1</tt> has been called.  Calls to other <tt>subtractive_rng</tt> objects
are irrelevant.  In implementation terms, this is because the class
<tt>subtractive_rng</tt> contains no <tt>static</tt> members.
<h3>See also</h3>
<A href="RandomNumberGenerator.html">Random Number Generator</A>

<HR SIZE="6"> <FONT SIZE="-2"> Copyright &copy; 1996 Silicon Graphics, Inc.
<HR>
<TABLE BORDER=0 WIDTH="100%" >
<TR>
<TD WIDTH="33%"><FONT SIZE=-1><A HREF="index.html" >
STL</A></FONT></TD>

<TD WIDTH="33%">
<CENTER><FONT SIZE=-2>&copy; Copyright 1997-1998 CodeGuru</FONT>&nbsp;</CENTER>
</TD>

<TD WIDTH="34%">
<DIV ALIGN=right><FONT SIZE=-1>Contact : <A HREF="mailto:webmaster@codeguru.com">webmaster@codeguru.com</A>&nbsp;</FONT></DIV>
</TD>
</TR>
</TABLE>
<SCRIPT LANGUAGE="JavaScript" ><!--
var adurl = "/cgi-bin/doubleclick.cgi?";

if( self.adcategory )
	adurl += adcategory;
else
	adurl += "mfc";

if( self.parent.norefreshad )
	parent.norefreshad = false;
else if( validframes )
	parent.frames['ad'].location = adurl;



if( !validframes && nfrm == -1)
{
	var dclkPage = "www.codeguru.com/";
	if( self.adcategory )
		dclkPage += adcategory;
	else 
		dclkPage += "mfc";
//	var random = Math.random();
	document.write('<nolayer><center>');
	document.write('<iframe src="http://ad.doubleclick.net/adi/' + dclkPage + ';ord='
	 + random + '" width=470 height=62 marginwidth=0 marginheight=0 hspace=0 vspace=0 '
	 + 'frameborder=0 scrolling=no bordercolor="#000000">');
	document.write('<a href="http://ad.doubleclick.net/jump/' + dclkPage + ';ord='
	 + random + '">');
	document.write('<img src="http://ad.doubleclick.net/ad/' + dclkPage + ';ord='
	 + random + '" height=60 width=468>' + '</a>');
	document.write('</iframe>');
	document.write('</center></nolayer>');
	document.write('<layer  src="http://ad.doubleclick.net/adl/' + dclkPage + 
	 ';ord=' + random + '"></layer>');
	document.write('<ilayer visibility=hide width=468 height=83></ilayer>');
}

// -->
</SCRIPT> 
<!-- SCRIPT LANGUAGE="JavaScript" SRC="/global/fscript.js">
//
</SCRIPT --> 

<noscript>
<p align="center">
<a href="http://ad.doubleclick.net/jump/www.codeguru.com/cpp;ord=Nupbz9FCY34AAHkzk98">
<img src="http://ad.doubleclick.net/ad/www.codeguru.com/cpp;ord=Nupbz9FCY34AAHkzk98"></a>
</p>
</noscript>





</BODY>
</HTML>
⌨️ 快捷键说明

复制代码 Ctrl + C
搜索代码 Ctrl + F
全屏模式 F11
切换主题 Ctrl + Shift + D
显示快捷键 ?
增大字号 Ctrl + =
减小字号 Ctrl + -