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<TD class=v2 vAlign=top><A class=v1
href="http://proquest.safaribooksonline.com/JVXSL.asp?x=1&mode=section&sortKey=title&sortOrder=asc&view=&xmlid=0-59600-214-9&open=false&catid=&s=1&b=1&f=1&t=1&c=1&u=1&srchText=">Ruby
in a Nutshell</A><BR>By Yukihiro Matsumoto<BR></TD></TR>
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<TD class=v2> </TD></TR>
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<TD class=t1 vAlign=bottom>Chapter 2. Language
Basics</TD></TR></TBODY></TABLE>
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<TD vAlign=top><A name=ruby-CHP-2-SECT-3></A>
<H3 class=docSection1Title>2.3 Lexical Conventions</H3><A
name=IXT-2-126876></A>
<P class=docText>Ruby programs are composed of elements
already familiar to most programmers: lines, whitespace,
comments, identifiers, reserved words, literals, etc.
Particularly for those programmers coming from other scripting
languages such as Perl, Python or tcl, you'll find Ruby's
conventions familiar, or at least straightforward enough not
to cause much trouble. </P><A name=ruby-CHP-2-SECT-3.1></A>
<H4 class=docSection2Title>2.3.1 Whitespace</H4><A
name=IXT-2-126877></A>
<P class=docText>We'll leave the thorny questions like "How
much whitespace makes code more readable and how much is
distracting?" for another day. If you haven't already caught
onto this theme, the Ruby interpreter will do pretty much what
you expect with respect to whitespace in your code. </P>
<P class=docText><A name=IXT-2-126878></A><A
name=IXT-2-126879></A><A name=IXT-2-126880></A><A
name=IXT-2-126881></A>Whitespace characters such as spaces and
tabs are generally ignored in Ruby code, except when they
appear in strings. Sometimes, however, they are used to
interpret ambiguous statements. Interpretations of this sort
produce warnings when the <TT>-w</TT> option is enabled. </P>
<DL class=docList>
<DT><SPAN class=docPubcolor><SPAN class=docPubcolor><SPAN
class=docMonofont>a</SPAN></SPAN> <SPAN
class=docPubcolor><SPAN class=docMonofont>+</SPAN></SPAN>
<SPAN class=docPubcolor><SPAN
class=docMonofont>b</SPAN></SPAN></SPAN>
<DD>
<P class=docList>Interpreted as <TT>a+b</TT> (<TT>a</TT> is
a local variable) </P>
<DT><SPAN class=docPubcolor><SPAN class=docPubcolor><SPAN
class=docMonofont>a +b</SPAN></SPAN></SPAN>
<DD>
<P class=docList>Interpreted as <TT>a(+b)</TT> (<TT>a</TT>,
in this case, is a method call) </P></DD></DL><A
name=ruby-CHP-2-SECT-3.2></A>
<H4 class=docSection2Title>2.3.2 Line Endings</H4>
<P class=docText><A name=IXT-2-126882></A><A
name=IXT-2-126883></A><A name=IXT-2-126884></A><A
name=IXT-2-126885></A><A name=IXT-2-126886></A><A
name=IXT-2-126887></A>Ruby interprets semicolons and newline
characters as the ending of a statement. However, if Ruby
encounters operators, such as <TT>+</TT>, <TT>-</TT>, or
backslash at the end of a line, they indicate the continuation
of a statement. </P><A name=ruby-CHP-2-SECT-3.3></A>
<H4 class=docSection2Title>2.3.3 Comments</H4><A
name=IXT-2-126888></A>
<P class=docText><A name=IXT-2-126889></A>Comments are lines
of annotation within Ruby code that are ignored at runtime.
Comments extend from <TT>#</TT> to the end of the line. </P><PRE># This is a comment.</PRE>
<P class=docText><A name=IXT-2-126890></A><A
name=IXT-2-126891></A><A name=IXT-2-126892></A><A
name=IXT-2-126893></A>Ruby code can contain embedded documents
too. Embedded documents extend from a line beginning with
<TT>=begin</TT> to the next line beginning with <TT>=end</TT>.
<TT>=begin</TT> and <TT>=end</TT> must come at the beginning
of a line. </P><PRE>=begin
This is an embedded document.
=end</PRE><A name=ruby-CHP-2-SECT-3.4></A>
<H4 class=docSection2Title>2.3.4 Identifiers</H4><A
name=IXT-2-126894></A>
<P class=docText><A name=IXT-2-126895></A><A
name=IXT-2-126896></A><A name=IXT-2-126897></A><A
name=IXT-2-126898></A><A name=IXT-2-126899></A><A
name=IXT-2-126900></A><A name=IXT-2-126901></A>Identifiers are
names of variables, constants, and methods. Ruby distinguishes
between identifiers consisting of uppercase characters and
those of lowercase characters. Identifier names may consist of
alphanumeric characters and the underscore character <TT>( _
)</TT>. You can distinguish a variable's type by the initial
character of its identifier. </P><A
name=ruby-CHP-2-SECT-3.5></A>
<H4 class=docSection2Title>2.3.5 Reserved Words</H4><A
name=IXT-2-126902></A>
<P class=docText>The following list shows the reserved words
in Ruby:</P><A name=ch02-12-fm2xml></A>
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