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<HTML><HEAD><TITLE>Recipe 2.5. Operating on a Series of Integers (Perl Cookbook)</TITLE><METANAME="DC.title"CONTENT="Perl Cookbook"><METANAME="DC.creator"CONTENT="Tom Christiansen & Nathan Torkington"><METANAME="DC.publisher"CONTENT="O'Reilly & Associates, Inc."><METANAME="DC.date"CONTENT="1999-07-02T01:30:07Z"><METANAME="DC.type"CONTENT="Text.Monograph"><METANAME="DC.format"CONTENT="text/html"SCHEME="MIME"><METANAME="DC.source"CONTENT="1-56592-243-3"SCHEME="ISBN"><METANAME="DC.language"CONTENT="en-US"><METANAME="generator"CONTENT="Jade 1.1/O'Reilly DocBook 3.0 to HTML 4.0"><LINKREV="made"HREF="mailto:online-books@oreilly.com"TITLE="Online Books Comments"><LINKREL="up"HREF="ch02_01.htm"TITLE="2. Numbers"><LINKREL="prev"HREF="ch02_05.htm"TITLE="2.4. Converting Between Binary and Decimal"><LINKREL="next"HREF="ch02_07.htm"TITLE="2.6. Working with Roman Numerals"></HEAD><BODYBGCOLOR="#FFFFFF"><img alt="Book Home" border="0" src="gifs/smbanner.gif" usemap="#banner-map" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Perl Cookbook"><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><p><TABLEWIDTH="684"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch02_05.htm"TITLE="2.4. Converting Between Binary and Decimal"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 2.4. Converting Between Binary and Decimal"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1"><ACLASS="chapter"REL="up"HREF="ch02_01.htm"TITLE="2. Numbers"></A></FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch02_07.htm"TITLE="2.6. Working with Roman Numerals"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 2.6. Working with Roman Numerals"BORDER="0"></A></TD></TR></TABLE></DIV><DIVCLASS="sect1"><H2CLASS="sect1"><ACLASS="title"NAME="ch02-28282">2.5. Operating on a Series of Integers</A></H2><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch02-pgfId-371">Problem <ACLASS="indexterm"NAME="ch02-idx-1000008016-0"></A><ACLASS="indexterm"NAME="ch02-idx-1000008016-1"></A></A></H3><PCLASS="para">You want to perform an operation on all integers between X and Y, such as when you're working on a contiguous section of an array or in any situations where you want to process all numbers[<ACLASS="footnote"HREF="#ch02-pgfId-1000005950">2</A>] within a range.</P><BLOCKQUOTECLASS="footnote"><DIVCLASS="footnote"><PCLASS="para"><ACLASS="footnote"NAME="ch02-pgfId-1000005950">[2]</A> Okay, integers. It's hard to find all the reals. Just ask Cantor.</P></DIV></BLOCKQUOTE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch02-pgfId-1000005952">Solution</A></H3><PCLASS="para">Use a <CODECLASS="literal">for</CODE> loop, or <CODECLASS="literal">..</CODE> in conjunction with a <CODECLASS="literal">foreach</CODE> loop:</P><PRECLASS="programlisting">foreach ($X .. $Y) { # $_ is set to every integer from X to Y, inclusive}foreach $i ($X .. $Y) { # $i is set to every integer from X to Y, inclusive }for ($i = $X; $i <= $Y; $i++) { # $i is set to every integer from X to Y, inclusive}for ($i = $X; $i <= $Y; $i += 7) { # $i is set to every integer from X to Y, stepsize = 7}</PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch02-pgfId-413">Discussion</A></H3><PCLASS="para">The first two methods use the <CODECLASS="literal">$X .. $Y</CODE> construct, which creates a list of integers between <CODECLASS="literal">$X</CODE> and <CODECLASS="literal">$Y</CODE>. This uses a lot of memory when <CODECLASS="literal">$X</CODE> and <CODECLASS="literal">$Y</CODE> are far apart. (This is fixed in the 5.005 release.) When iterating over consecutive integers, the explicit <CODECLASS="literal">for</CODE> loop in the third method is more memory efficient.</P><PCLASS="para">The following code shows each technique. Here we only print the numbers we generate:</P><PRECLASS="programlisting">print "Infancy is: ";foreach (0 .. 2) { print "$_ ";}print "\n";print "Toddling is: ";foreach $i (3 .. 4) { print "$i ";}print "\n";print "Childhood is: ";for ($i = 5; $i <= 12; $i++) { print "$i ";}print "\n";<CODECLASS="userinput"><B><CODECLASS="replaceable"><I>Infancy is: 0 1 2 </I></CODE></B></CODE><CODECLASS="userinput"><B><CODECLASS="replaceable"><I>Toddling is: 3 4 </I></CODE></B></CODE><CODECLASS="userinput"><B><CODECLASS="replaceable"><I>Childhood is: 5 6 7 8 9 10 11 12 </I></CODE></B></CODE></PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch02-pgfId-1000007965">See Also</A></H3><PCLASS="para">The <CODECLASS="literal">for</CODE> and <CODECLASS="literal">foreach</CODE> operators in <EMCLASS="emphasis">perlsyn </EM>(1) and the <ACLASS="olink"HREF="../prog/ch02_06.htm#PERL2-CH-2-SECT-6.4.2">"For Loops"</A> and <ACLASS="olink"HREF="../prog/ch02_06.htm#PERL2-CH-2-SECT-6.4.3">"Foreach Loops"</A> sections of <ACLASS="olink"HREF="../prog/ch02_01.htm">Chapter 2</A> of <ACLASS="citetitle"HREF="../prog/index.htm"TITLE="Programming Perl"><CITECLASS="citetitle">Programming Perl</CITE></A><ACLASS="indexterm"NAME="ch02-idx-1000008019-0"></A></P></DIV></DIV><DIVCLASS="htmlnav"><P></P><HRALIGN="LEFT"WIDTH="684"TITLE="footer"><TABLEWIDTH="684"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch02_05.htm"TITLE="2.4. 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