diff options
| -rw-r--r-- | lisplib.c | 2 | ||||
| -rw-r--r-- | share/txr/stdlib/place.tl | 13 | ||||
| -rw-r--r-- | txr.1 | 31 |
3 files changed, 45 insertions, 1 deletions
@@ -69,7 +69,7 @@ static val place_set_entries(val dlt, val fun) lit("with-delete-expander"), lit("set"), lit("pset"), lit("zap"), lit("flip"), lit("inc"), lit("dec"), lit("push"), lit("pop"), lit("swap"), lit("shift"), lit("rotate"), - lit("pushnew"), lit("del"), + lit("pushnew"), lit("del"), lit("lset"), lit("defplace"), lit("define-place-macro"), lit("define-modify-macro"), lit("placelet"), lit("placelet*"), lit("define-acessor"), lit("with-slots"), diff --git a/share/txr/stdlib/place.tl b/share/txr/stdlib/place.tl index 7ef7f44d..5d17acb7 100644 --- a/share/txr/stdlib/place.tl +++ b/share/txr/stdlib/place.tl @@ -295,6 +295,19 @@ (with-delete-expander (deleter) place env ^(,deleter))) +(defmacro lset (. places-source) + (let ((places (butlast places-source)) + (source (last places-source)) + (orig (gensym)) + (iter (gensym))) + (unless places + (sys:eval-err "lset: require one or more places followed by expression")) + ^(let* ((,orig ,(car source)) + (,iter ,orig)) + ,*(butlast (mappend (ret ^((set ,@1 (car ,iter)) (set ,iter (cdr ,iter)))) + places)) + ,orig))) + (defmacro defplace (place-destructuring-args body-sym (getter-sym setter-sym update-body) : ((ssetter-sym clobber-body)) @@ -25452,6 +25452,37 @@ place denotes a value stored in a dynamic data set such as a hash table, then deletion of that place implies deletion of the entry which holds that value. If the entry is identified by a key, that key is also removed. +.coNP Macro @ lset +.synb +.mets (lset <> { place }+ << list-expr ) +.syne +.desc +The +.code lset +operator's parameter list consists of one or more places followed +by an expression +.metn list-expr . + +The macro evaluates +.codn list-expr , +which is expected to produce a proper list. + +Successive elements of the resulting list are then assigned to each +successive +.codn place . + +If there are fewer elements in the list than places, the +unmatched places receive the value +.codn nil . + +Excess elements in the list are ignored. + +A +.code lset +form produces the value of +.meta list-expr +as its result value. + .SS* User-Defined Places and Place Operators \*(TL provides a number of place-modifying operators such as .codn set , |