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<HTML><TITLE>Basic Syntax and I/O: Double Quotes</TITLE><BODY BGCOLOR="#FFF0E0" VLINK="#0FBD0F" TEXT="#101000" LINK="#0F0FDD">
<A NAME="top"><H1>Double Quotes</H1></A>


<P> Double quotes in Tcl have a meaning that is both familiar and strange.  Often,
they are used to define strings, as in <TT>"Hello World"</TT> &#150; that is what is
familiar.  A cleaner way to write the same string is usually <TT>{Hello
World}</TT> -- that is what is strange.

<P> You saw the use of curly brackets in the previous section.  Double quotes are
much the same but different in that:

<UL>

<P> <P><LI> When an argument is surrounded by double quotes, substitutions <CITE>are</CITE>
performed &#150; use the curly brackets when you do not want substitution and use
double quotes when you do.  

<P> <P><LI> Curly brackets can be nested whereas double quotes cannot.

</UL>

<DL><DD> <CITE>Be aware that it is what surrounds your argument that determines
whether curly-bracket or double-quote processing will apply.</CITE>
<P> </DL>

<P>  <P><A NAME="2.6a">
<STRONG>Exercise 2.6a</STRONG> </A><DL><DD>
  What is output by the following?

<PRE>
set X Hello
puts {$X World}
puts "$X World"
puts { {Hello} {World} }
puts " {Hello} {World} "
</PRE> 
<P>
<A HREF="2.11.html#Sol2.6a" tppabs="http://www.mapfree.com/sbf/tcl/book/select/Html/2.11.html#Sol2.6a">Solution</A></DL>
 

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<I>Jun 17, 1998</I>
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