<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <HTML> <HEAD> <META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9"> <TITLE> A Guide to the S-Lang Language: Identifiers</TITLE> <LINK HREF="slang-6.html" REL=next> <LINK HREF="slang-4.html" REL=previous> <LINK HREF="slang.html#toc5" REL=contents> </HEAD> <BODY> <A HREF="slang-6.html">Next</A> <A HREF="slang-4.html">Previous</A> <A HREF="slang.html#toc5">Contents</A> <HR> <H2><A NAME="s5">5. Identifiers</A></H2> <P> <P>The names given to variables, functions, and data types are called <EM>identifiers</EM>. There are some restrictions upon the actual characters that make up an identifier. An identifier name must start with a letter (<CODE>[A-Za-z]</CODE>), an underscore character, or a dollar sign. The rest of the characters in the name can be any combination of letters, digits, dollar signs, or underscore characters. However, all identifiers whose name begins with two underscore characters are reserved for internal use by the interpreter and declarations of objects with such names should be avoided. <P>Examples of valid identifiers include: <BLOCKQUOTE><CODE> <PRE> mary _3 _this_is_ok a7e1 $44 _44$_Three </PRE> </CODE></BLOCKQUOTE> However, the following are not legal: <BLOCKQUOTE><CODE> <PRE> 7abc 2e0 #xx </PRE> </CODE></BLOCKQUOTE> In fact, <CODE>2e0</CODE> actually specifies the real number <CODE>2.0</CODE>. <P>Although the maximum length of identifiers is unspecified by the language, the length should be kept below <CODE>64</CODE> characters. <P>The following identifiers are reserved by the language for use as keywords: <BLOCKQUOTE><CODE> <PRE> !if _for do mod sign xor ERROR_BLOCK abs do_while mul2 sqr public EXIT_BLOCK and else not static private USER_BLOCK0 andelse exch or struct USER_BLOCK1 break for orelse switch USER_BLOCK2 case foreach pop typedef USER_BLOCK3 chs forever return using USER_BLOCK4 continue if shl variable __tmp define loop shr while </PRE> </CODE></BLOCKQUOTE> <P> <HR> <A HREF="slang-6.html">Next</A> <A HREF="slang-4.html">Previous</A> <A HREF="slang.html#toc5">Contents</A> </BODY> </HTML>