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cl:types:boolean [2017/05/01 21:00] (current)
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 +====== Type BOOLEAN ======
 +
 +====Supertypes====
 +**boolean**,​ **[[CL:​Types:​symbol]]**,​ **[[CL:​Types:​t]]**
 +
 +====Description====
 +The type **boolean** contains the //​[[CL:​Glossary:​symbols]]//​ **[[CL:​Constant Variables:​t]]** and **[[CL:​Constant Variables:​nil]]**,​ which represent true and false, respectively.
 +
 +====See Also====
 +  * **[[CL:​Constant Variables:​t|Constant Variable T]]**
 +  * **[[CL:​Constant Variables:​nil|Constant Variable NIL]]**
 +  * **[[CL:​Special Operators:​if|Special Operator IF]]**
 +  * **[[CL:​Functions:​not|Function NOT]]**
 +  * **[[CL:​Functions:​complement|Function COMPLEMENT]]**
 +
 +====Notes====
 +Conditional operations, such as **[[CL:​Special Operators:​if]]**,​ permit the use of //​[[CL:​Glossary:​generalized booleans]]//,​ not just //​[[CL:​Glossary:​booleans]]//;​ any //​[[CL:​Glossary:​non-nil]]//​ value, not just **[[CL:​Constant Variables:​t]]**,​ counts as true for a //​[[CL:​Glossary:​generalized boolean]]//​. However, as a matter of convention, the //​[[CL:​Glossary:​symbol]]//​ **[[CL:​Constant Variables:​t]]** is considered the canonical value to use even for a //​[[CL:​Glossary:​generalized boolean]]// when no better choice presents itself.
 +