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<HTML><HEAD><TITLE>Recipe 2.6. Working with Roman Numerals (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="1999-07-02T01:30:08Z"><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_06.htm"TITLE="2.5. Operating on a Series of Integers"><LINKREL="next"HREF="ch02_08.htm"TITLE="2.7. Generating Random Numbers"></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_06.htm"TITLE="2.5. Operating on a Series of Integers"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 2.5. Operating on a Series of Integers"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_08.htm"TITLE="2.7. Generating Random Numbers"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 2.7. Generating Random Numbers"BORDER="0"></A></TD></TR></TABLE></DIV><DIVCLASS="sect1"><H2CLASS="sect1"><ACLASS="title"NAME="ch02-21463">2.6. Working with Roman Numerals</A></H2><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch02-pgfId-473">Problem <ACLASS="indexterm"NAME="ch02-idx-1000008023-0"></A><ACLASS="indexterm"NAME="ch02-idx-1000008023-1"></A><ACLASS="indexterm"NAME="ch02-idx-1000008023-2"></A></A></H3><PCLASS="para">You want to convert between regular numbers and Roman numerals. You need to do this with items in outlines, page numbers on a preface, and copyrights for movie credits.</P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch02-pgfId-479">Solution</A></H3><PCLASS="para">Use the <ACLASS="indexterm"NAME="ch02-idx-1000008029-0"></A>Roman module from CPAN:</P><PRECLASS="programlisting">use Roman;$roman = roman($arabic); # convert to roman numerals$arabic = arabic($roman) if isroman($roman); # convert from roman numerals</PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch02-pgfId-491">Discussion</A></H3><PCLASS="para">The Roman module provides both <CODECLASS="literal">Roman</CODE> and <CODECLASS="literal">roman</CODE><ACLASS="indexterm"NAME="ch02-idx-1000008030-0"></A> for converting Arabic ("normal") numbers to their Roman equivalents. <CODECLASS="literal">Roman</CODE> produces uppercase letters, whereas <CODECLASS="literal">roman</CODE> gives lowercase ones.</P><PCLASS="para">The module only deals with Roman numbers from 1 to 3999, inclusive. The Romans didn't represent negative numbers or zero, and 5000 (which 4000 is represented in terms of) uses a symbol outside the ASCII character set.</P><PRECLASS="programlisting">use Roman;$roman_fifteen = roman(15); # "xv"print "Roman for fifteen is $roman_fifteen\n";$arabic_fifteen = arabic($roman_fifteen);print "Converted back, $roman_fifteen is $arabic_fifteen\n";<CODECLASS="userinput"><B><CODECLASS="replaceable"><I>Roman for fifteen is xv</I></CODE></B></CODE><CODECLASS="userinput"><B><CODECLASS="replaceable"><I>Converted back, xv is 15</I></CODE></B></CODE></PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch02-pgfId-515">See Also</A></H3><PCLASS="para">The Encyclopaedia Brittanica article on "Mathematics, History Of "; the documentation with the Roman module; <ACLASS="xref"HREF="ch06_24.htm"TITLE="Regular Expression Grabbag">Recipe 6.23</A> <ACLASS="indexterm"NAME="ch02-idx-1000008025-0"></A><ACLASS="indexterm"NAME="ch02-idx-1000008025-1"></A><ACLASS="indexterm"NAME="ch02-idx-1000008025-2"></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_06.htm"TITLE="2.5. Operating on a Series of Integers"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 2.5. Operating on a Series of Integers"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><ACLASS="book"HREF="index.htm"TITLE="Perl Cookbook"><IMGSRC="../gifs/txthome.gif"ALT="Perl Cookbook"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch02_08.htm"TITLE="2.7. Generating Random Numbers"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 2.7. Generating Random Numbers"BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228">2.5. Operating on a Series of Integers</TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><ACLASS="index"HREF="index/index.htm"TITLE="Book Index"><IMGSRC="../gifs/index.gif"ALT="Book Index"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228">2.7. 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