diff options
| -rw-r--r-- | lisplib.c | 2 | ||||
| -rw-r--r-- | share/txr/stdlib/yield.tl | 28 | ||||
| -rw-r--r-- | txr.1 | 22 |
3 files changed, 51 insertions, 1 deletions
@@ -299,7 +299,7 @@ static val yield_set_entries(val dlt, val fun) val name[] = { lit("obtain"), lit("obtain-block"), lit("yield-from"), lit("yield"), lit("obtain*"), lit("obtain*-block"), - lit("suspend"), + lit("suspend"), lit("hlet"), lit("hlet*"), nil }; set_dlt_entries(dlt, name, fun); diff --git a/share/txr/stdlib/yield.tl b/share/txr/stdlib/yield.tl index 3ab74745..f8b5783d 100644 --- a/share/txr/stdlib/yield.tl +++ b/share/txr/stdlib/yield.tl @@ -88,3 +88,31 @@ ^(sys:capture-cont ',name (lambda (,sym) (sys:abscond-from ,name (progn ,*body))) ',form)) + +(defun hlet-expand (op raw-vis body) + (let* ((vis (mapcar [iffi atom list] raw-vis)) + (nvars (len vis)) + (syms [mapcar car vis]) + (inits [mapcar cadr vis]) + (letop (if (eq op 'hlet*) 'let* 'let)) + (gens (mapcar (ret (gensym)) vis)) + (vec (gensym)) + (macs (mapcar (ret ^(,@1 (vecref ,vec ,@2))) + syms (range 0))) + (inits (mapcar (ret ^(set (vecref ,vec ,@1) ,@2)) + (range 0) inits))) + (if (eq op 'hlet*) + ^(let* ((,vec (vector ,nvars))) + (symacrolet ,macs + ,*inits + ,*body)) + ^(let* ((,vec (vector ,nvars))) + ,*inits + (symacrolet ,macs + ,*body))))) + +(defmacro hlet (var-inits . body) + (hlet-expand 'hlet var-inits body)) + +(defmacro hlet* (var-inits . body) + (hlet-expand 'hlet* var-inits body)) @@ -38563,6 +38563,28 @@ non-deterministically: -> (2 4) .cble +.coNP Macros @ hlet and @ hlet* +.synb +.mets (hlet >> ({ sym | >> ( sym << init-form )}*) << body-form *) +.mets (hlet* >> ({ sym | >> ( sym << init-form )}*) << body-form *) +.syne +.desc +The +.code hlet +and +.code hlet* +macros behave exactly like +.code let +and +.codn let* , +respectively except that they guarantee that the variable bindings are +allocated in storage which isn't captured by delimited continuations. + +The +.code h +in the names stands for "heap", serving as a mnemonic based on the +implementation concept of these bindings being "heap allocated". + .SS* Regular Expression Library \*(TX provides a "pure" regular expression implementation based on automata |