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cl:functions:clear-input [2019/06/15 02:00] |
cl:functions:clear-input [2019/09/16 13:00] (current) |
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| + | ====== Function CLEAR-INPUT ====== | ||
| + | |||
| + | ====Syntax==== | ||
| + | * **clear-input** ''&optional'' //input-stream// → **[[CL:Constant Variables:nil]]** | ||
| + | |||
| + | ====Arguments and Values==== | ||
| + | * //input-stream// - an //[[CL:Glossary:input]]// //[[CL:Glossary:stream designator]]//. The default is //[[CL:Glossary:standard input]]//. | ||
| + | |||
| + | ====Description==== | ||
| + | Clears any available input from //input-stream//. | ||
| + | |||
| + | If **clear-input** does not make sense for //input-stream//, then **clear-input** does nothing. | ||
| + | |||
| + | ====Examples==== | ||
| + | The exact I/O behavior of this example might vary from //[[CL:Glossary:implementation]]// to //[[CL:Glossary:implementation]]// depending on the kind of //[[CL:Glossary:interactive]]// buffering that occurs. (The call to **[[CL:Functions:sleep]]** here is intended to help even out the differences in //[[CL:Glossary:implementation|implementations]]// which do not do line-at-a-time buffering.) | ||
| + | |||
| + | <blockquote> | ||
| + | ([[CL:Macros:defun]] read-sleepily (&optional (clear-p [[CL:Constant Variables:nil]]) (zzz 0)) | ||
| + | ([[CL:Functions:list]] ([[CL:Special Operators:progn]] ([[CL:Functions:print]] '>) | ||
| + | ([[CL:Functions:read]])) ;; Note that input typed within the first | ||
| + | ;; ZZZ seconds will be discarded. | ||
| + | ([[CL:Special Operators:progn]] ([[CL:Functions:print]] '>) | ||
| + | ([[CL:Macros:when]] zzz ([[CL:Functions:sleep]] zzz)) | ||
| + | ([[CL:Functions:print]] '>>) | ||
| + | ([[CL:Macros:when]] clear-p (clear-input)) | ||
| + | ([[CL:Functions:read]])))) | ||
| + | |||
| + | (read-sleepily) | ||
| + | <o>> __10__ | ||
| + | > | ||
| + | >> __20__ </o> | ||
| + | → (10 20) | ||
| + | |||
| + | (read-sleepily t) | ||
| + | <o>> __10__ | ||
| + | > | ||
| + | >> __20__ </o> | ||
| + | → (10 20) | ||
| + | |||
| + | (read-sleepily t 10) | ||
| + | <o>> __10__ | ||
| + | > __20__ ; Some implementations won't echo typeahead here. | ||
| + | >> __30__ </o> | ||
| + | → (10 30) | ||
| + | </blockquote> | ||
| + | |||
| + | ====Side Effects==== | ||
| + | The //input-stream// is modified. | ||
| + | |||
| + | ====Affected By==== | ||
| + | **[[CL:Variables:star-standard-input-star|*standard-input*]]** | ||
| + | |||
| + | ====Exceptional Situations==== | ||
| + | Should signal an error of type type-error if //input-stream// is not a //[[CL:Glossary:stream designator]]//. | ||
| + | |||
| + | ====See Also==== | ||
| + | * **[[CL:Functions:clear-output|Function CLEAR-OUTPUT]]** | ||
| + | |||
| + | ====Notes==== | ||
| + | None. | ||
| + | |||
