<!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <meta name="generator" content="hevea 2.00"> <link rel="stylesheet" type="text/css" href="manual.css"> <title>Constants</title> </head> <body> <a href="types.html"><img src="previous_motif.gif" alt="Previous"></a> <a href="language.html"><img src="contents_motif.gif" alt="Up"></a> <a href="patterns.html"><img src="next_motif.gif" alt="Next"></a> <hr> <h2 class="section" id="sec102">6.5  Constants</h2> <table class="display dcenter"><tr class="c026"><td class="dcell"><table class="c002 cellpading0"><tr><td class="c025"> <a class="syntax" id="constant"><span class="c014">constant</span></a></td><td class="c022">::=</td><td class="c024"> <a class="syntax" href="lex.html#integer-literal"><span class="c014">integer-literal</span></a>  </td></tr> <tr><td class="c025"> </td><td class="c022">∣</td><td class="c024"> <a class="syntax" href="lex.html#float-literal"><span class="c014">float-literal</span></a>  </td></tr> <tr><td class="c025"> </td><td class="c022">∣</td><td class="c024"> <a class="syntax" href="lex.html#char-literal"><span class="c014">char-literal</span></a>  </td></tr> <tr><td class="c025"> </td><td class="c022">∣</td><td class="c024"> <a class="syntax" href="lex.html#string-literal"><span class="c014">string-literal</span></a>  </td></tr> <tr><td class="c025"> </td><td class="c022">∣</td><td class="c024"> <a class="syntax" href="names.html#constr"><span class="c014">constr</span></a>  </td></tr> <tr><td class="c025"> </td><td class="c022">∣</td><td class="c024"> <span class="c008">false</span>  </td></tr> <tr><td class="c025"> </td><td class="c022">∣</td><td class="c024"> <span class="c008">true</span>  </td></tr> <tr><td class="c025"> </td><td class="c022">∣</td><td class="c024"> <span class="c008">()</span>  </td></tr> <tr><td class="c025"> </td><td class="c022">∣</td><td class="c024"> <span class="c008">begin</span> <span class="c008">end</span>  </td></tr> <tr><td class="c025"> </td><td class="c022">∣</td><td class="c024"> <span class="c008">[]</span>  </td></tr> <tr><td class="c025"> </td><td class="c022">∣</td><td class="c024"> <span class="c008">[||]</span>  </td></tr> <tr><td class="c025"> </td><td class="c022">∣</td><td class="c024"> <span class="c008">`</span><a class="syntax" href="names.html#tag-name"><span class="c014">tag-name</span></a> </td></tr> </table></td></tr> </table><p>The syntactic class of constants comprises literals from the four base types (integers, floating-point numbers, characters, character strings), and constant constructors from both normal and polymorphic variants, as well as the special constants <span class="c008">false</span>, <span class="c008">true</span>, <span class="c008">()</span>, <span class="c008">[]</span>, and <span class="c008">[||]</span>, which behave like constant constructors, and <span class="c005"><span class="c007">begin</span> <span class="c007">end</span></span>, which is equivalent to <span class="c008">()</span>. </p> <hr> <a href="types.html"><img src="previous_motif.gif" alt="Previous"></a> <a href="language.html"><img src="contents_motif.gif" alt="Up"></a> <a href="patterns.html"><img src="next_motif.gif" alt="Next"></a> </body> </html>
