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<h2 class="section" id="s:const"><a class="section-anchor" href="#s:const" aria-hidden="true"></a>7.5 Constants</h2>
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<a id="hevea_manual.kwd14"></a></p><div class="syntax"><table class="display dcenter"><tr class="c019"><td class="dcell"><table class="c001 cellpading0"><tr><td class="c018">
<a class="syntax" id="constant"><span class="c010">constant</span></a></td><td class="c015">::=</td><td class="c017">
<a class="syntax" href="lex.html#integer-literal"><span class="c010">integer-literal</span></a>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <a class="syntax" href="lex.html#int32-literal"><span class="c010">int32-literal</span></a>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <a class="syntax" href="lex.html#int64-literal"><span class="c010">int64-literal</span></a>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <a class="syntax" href="lex.html#nativeint-literal"><span class="c010">nativeint-literal</span></a>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <a class="syntax" href="lex.html#float-literal"><span class="c010">float-literal</span></a>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <a class="syntax" href="lex.html#char-literal"><span class="c010">char-literal</span></a>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <a class="syntax" href="lex.html#string-literal"><span class="c010">string-literal</span></a>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <a class="syntax" href="names.html#constr"><span class="c010">constr</span></a>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <span class="c004">false</span>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <span class="c004">true</span>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <span class="c004">()</span>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <span class="c004">begin</span> <span class="c004">end</span>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <span class="c004">[]</span>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <span class="c004">[||]</span>
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <span class="c004">`</span><a class="syntax" href="names.html#tag-name"><span class="c010">tag-name</span></a>
</td></tr>
</table></td></tr>
</table></div><p>
See also the following language extension:
<a href="extensionsyntax.html#ss%3Aextension-literals">extension literals</a>.</p><p>The syntactic class of constants comprises literals from the four
base types (integers, floating-point numbers, characters, character
strings), the integer variants, and constant constructors
from both normal and polymorphic variants, as well as the special
constants <span class="c004">false</span>, <span class="c004">true</span>, <span class="c004">()</span>,
<span class="c004">[]</span>, and <span class="c004">[||]</span>, which behave like constant constructors, and
<span class="c002"><span class="c003">begin</span> <span class="c003">end</span></span>, which is equivalent to <span class="c004">()</span>.
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