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cl:functions:random [2019/09/14 05:00] |
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| + | ====== Function RANDOM ====== | ||
| + | |||
| + | ====Syntax==== | ||
| + | * **random** //limit ''&optional'' random-state// → //random-number// | ||
| + | |||
| + | ====Arguments and Values==== | ||
| + | * //limit// - a positive //[[CL:Glossary:integer]]//, or a positive //[[CL:Glossary:float]]//. | ||
| + | * //random-state// - a //[[CL:Glossary:random state]]//. The default is the //[[CL:Glossary:current random state]]//. | ||
| + | * //random-number// - a non-negative //[[CL:Glossary:number]]// less than //limit// and of the same //[[CL:Glossary:type]]// as //limit//. | ||
| + | |||
| + | ====Description==== | ||
| + | Returns a pseudo-random number that is a non-negative //[[CL:Glossary:number]]// less than //limit// and of the same //[[CL:Glossary:type]]// as //limit//. | ||
| + | |||
| + | The //random-state//, which is modified by this function, encodes the internal state maintained by the random number generator. | ||
| + | |||
| + | An approximately uniform choice distribution is used. If //limit// is an //[[CL:Glossary:integer]]//, each of the possible results occurs with (approximate) probability ''1<nowiki>/</nowiki>//limit//''. | ||
| + | |||
| + | ====Examples==== | ||
| + | |||
| + | <blockquote> | ||
| + | ([[CL:Functions:math-not-greater|<=]] 0 (random 1000) 1000) <r>//[[CL:Glossary:true]]// </r> | ||
| + | ([[CL:Special Operators:let]] ((state1 ([[CL:Functions:make-random-state]])) | ||
| + | (state2 ([[CL:Functions:make-random-state]]))) | ||
| + | ([[CL:Functions:math-equal|=]] (random 1000 state1) (random 1000 state2))) <r>//[[CL:Glossary:true]]//</r> | ||
| + | </blockquote> | ||
| + | |||
| + | ====Side Effects==== | ||
| + | The //random-state// is modified. | ||
| + | |||
| + | ====Affected By==== | ||
| + | None. | ||
| + | |||
| + | ====Exceptional Situations==== | ||
| + | Should signal an error of type type-error if //limit// is not a positive //[[CL:Glossary:integer]]// or a positive //[[CL:Glossary:real]]//. | ||
| + | |||
| + | ====See Also==== | ||
| + | * **[[CL:Functions:make-random-state|Function MAKE-RANDOM-STATE]]** | ||
| + | * **[[CL:Variables:star-random-state-star|Variable *RANDOM-STATE*]]** | ||
| + | |||
| + | ====Notes==== | ||
| + | See //Common Lisp the Language// for information about generating random numbers. | ||
| + | |||
