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<TITLE>Example Function: Split a Line into Words</TITLE>
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<H2>12.3 Example Function: Split a Line into Words</H2>
<A NAME="idx240"><!></A>
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<P>In this section we illustrate the use of some of the <B><I><A HREF="../stdlibref/basic-string.html">string</A></I></B> functions by defining a function to split a line of text into individual words. We have already made use of this function in the concordance example program in <A HREF="9-3.html#933">Section&nbsp;9.3.3</A>.</P>
<BLOCKQUOTE><HR><B>
NOTE -- The split function is in the concordance program in file concord.cpp.
</B><HR></BLOCKQUOTE>
<P>There are three arguments to this function. The first two are <B><I><A HREF="../stdlibref/basic-string.html">string</A></I></B>s, describing the line of text and the separators to be used to differentiate words, respectively. The third argument is a <B><I><A HREF="../stdlibref/list.html">list</A></I></B> of <B><I>string</I></B>s, used to return the individual words in the line.</P>

<UL><PRE>
void split (const std::string&amp; text, const std::string&amp; separators,
            std::list&lt;std::string,
                      std::allocator&lt;std::string&gt; &gt;&amp; words) {

    size_t n     = text.length ();
    size_t start = text.find_first_not_of (separators);

    while (start &lt; n) {
        size_t stop = text.find_first_of (separators, start);
        if (stop &gt; n) stop = n;
        words.push_back (text.substr (start, stop-start));
        start = text.find_first_not_of (separators, stop+1);
    }
}
</PRE></UL>
<P>The program begins by finding <SAMP>start</SAMP>, the index of the first character that is <I>not</I> a separator. The loop then looks for <SAMP>stop</SAMP>, the index of the next character that <I>is</I> a separator, or uses the end of the string if no such value is found. These two indexes delimit a word, which is copied out of the text using a substring operation and inserted into the <B><I><A HREF="../stdlibref/list.html">list</A></I></B> of words. A search is then made to discover the start of the next word, and the loop continues. When the index value exceeds the limits of the <B><I><A HREF="../stdlibref/basic-string.html">string</A></I></B>, execution stops.</P>


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