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cl:macros:push [2019/12/05 03:00] |
cl:macros:push [2020/07/14 02:00] (current) |
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| + | ====== Macro PUSH ====== | ||
| + | ====Syntax==== | ||
| + | * **push** //item place// → //new-place-value// | ||
| + | |||
| + | ====Arguments and Values==== | ||
| + | * //item//---an //[[CL:Glossary:object]]//. | ||
| + | * //place//---a //[[CL:Glossary:place]]//, the //[[CL:Glossary:value]]// of which may be any //[[CL:Glossary:object]]//. | ||
| + | * //new-place-value//---a //[[CL:Glossary:list]]// (the new //[[CL:Glossary:value]]// of //place//). | ||
| + | |||
| + | ====Description==== | ||
| + | **push** prepends //item// to the //[[CL:Glossary:list]]// that is stored in //place//, stores the resulting //[[CL:Glossary:list]]// in //place//, and returns the //[[CL:Glossary:list]]//. | ||
| + | |||
| + | For information about the //[[CL:Glossary:evaluation]]// of //[[CL:Glossary:subforms]]// of //place//, \seesection\GenRefSubFormEval. | ||
| + | |||
| + | ====Examples==== | ||
| + | <blockquote> | ||
| + | ([[CL:Macros:defparameter]] *list-in-list* '(nil)) <r>*LIST-IN-LIST*</r> | ||
| + | (push 1 ([[CL:Functions:car]] *list-in-list*)) <r>(1)</r> | ||
| + | *list-in-list* <r>((1))</r> | ||
| + | (push 1 ([[CL:Functions:car]] *list-in-list*)) <r>(1 1)</r> | ||
| + | *list-in-list* <r>((1 1))</r> | ||
| + | ([[CL:Macros:defparameter]] *x* '(a (b c) d)) <r>*X*</r> | ||
| + | (push 5 ([[CL:Functions:cadr]] *x*)) <r>(5 B C) </r> | ||
| + | *x* <r>(A (5 B C) D)</r> | ||
| + | </blockquote> | ||
| + | |||
| + | ====Side Effects==== | ||
| + | The contents of //place// are modified. | ||
| + | |||
| + | ====Affected By==== | ||
| + | None. | ||
| + | |||
| + | ====Exceptional Situations==== | ||
| + | None. | ||
| + | |||
| + | ====See Also==== | ||
| + | **[[CL:Macros:pop]]**, **[[CL:Macros:pushnew]]**, {\secref\GeneralizedReference} | ||
| + | |||
| + | ====Example Implementation==== | ||
| + | To be done. | ||
| + | |||
| + | The effect of ''(push //item// //place//)'' is equivalent to | ||
| + | |||
| + | <blockquote> | ||
| + | ([[CL:Macros:setf]] //place// ([[CL:Functions:cons]] //item// //place//)) | ||
| + | </blockquote> | ||
| + | |||
| + | except that the //[[CL:Glossary:subforms]]// of //place// are evaluated only once, and //item// is evaluated before //place//. | ||
| + | |||
| + | ====Notes==== | ||
| + | None. | ||
| + | |||
| + | \issue{PUSH-EVALUATION-ORDER:FIRST-ITEM} | ||
| + | \issue{DOTTED-LIST-ARGUMENTS:CLARIFY} | ||
