70 lines
2.4 KiB
HTML
70 lines
2.4 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN">
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<!Originally converted to HTML using LaTeX2HTML 95 (Thu Jan 19 1995) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds >
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<HEAD>
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<TITLE> Strings</TITLE>
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</HEAD>
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<BODY>
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<meta name="description" value=" Strings">
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<meta name="keywords" value="lp">
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<meta name="resource-type" value="document">
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<meta name="distribution" value="global">
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<P>
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<BR> <HR>
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<A HREF="node56.html"><IMG ALIGN=BOTTOM ALT="next" SRC="next_motif.gif"></A>
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<A HREF="node53.html"><IMG ALIGN=BOTTOM ALT="up" SRC="up_motif.gif"></A>
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<A HREF="node54.html"><IMG ALIGN=BOTTOM ALT="previous" SRC="previous_motif.gif"></A> <BR>
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<A HREF="lp.html"><B>Contents</B></A>
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<B> Next:</B>
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<A HREF="node56.html"> Defstruct</A>
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<B>Up:</B>
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<A HREF="node53.html"> ArraysVectors, and </A>
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<B> Previous:</B>
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<A HREF="node54.html"> Arrays and Vectors</A>
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<BR> <HR> <P>
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<H2> Strings</H2>
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<P>
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A string in Lisp is represented by characters surrounded by double quotes: <tt> "</tt>. Strings are very useful for manipulating chunks of text. They are also used by Common Lisp to manage input and output.
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<P>
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Technically strings are arrays, but it is probably best (at first) to ignore this fact and treat them as a separate data type. Typing a string directly to the interpreter simply causes the interpreter to return the string:
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<P>
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<BLOCKQUOTE>
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<PRE>> "This is a string"
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"This is a string"
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</PRE>
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</BLOCKQUOTE>
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Notice that the string may contain spaces, and that the distinction between upper and lowercase letters is preserved. A string is completely opaque to the interpreter and may contain punctuation marks and even new lines:
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<P>
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<BLOCKQUOTE>
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<PRE>> "This is a larger piece of text.
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It contains a few, otherwise unmanageable
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punctuation marks. It can even have blank lines:
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^Like these!"
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"This is a larger piece of text.
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It contains a few, otherwise unmanageable
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punctuation marks. It can even have blank lines:
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^Like these!"
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</PRE>
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</BLOCKQUOTE>
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Strings can also be included as elements of lists. For example:
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<P>
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<BLOCKQUOTE>
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<PRE>> (cons "this" '(here))
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("this" HERE)
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</PRE>
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</BLOCKQUOTE>
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Strings are very useful for giving nicely formatted responses to user commands. This will be explored in the next chapter.
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<P>
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<BR> <HR>
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<P>
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<ADDRESS>
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<I>© Colin Allen & Maneesh Dhagat <BR>
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March 2007 </I>
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</ADDRESS>
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</BODY>
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