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Made ac.scm more amenable to module/namespace manipulation from Arc, and added lib/ns.arc.
1 parent e4be1f5 commit e2208c2

3 files changed

Lines changed: 771 additions & 17 deletions

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‎ac.scm‎

Lines changed: 72 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -9,6 +9,8 @@
99
(require (lib "foreign.ss"))
1010
(unsafe!)
1111

12+
(define main-namespace (current-namespace))
13+
1214
(define (ac-global-name s)
1315
(string->symbol (string-append "_" (symbol->string s))))
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@@ -22,7 +24,13 @@
2224
(defarc arc-name scheme-name)))
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((defarc arc-name scheme-name)
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(define (scheme-name . args)
25-
(apply (namespace-variable-value (ac-global-name 'arc-name)) args)))
27+
28+
; The following 'parameterize has been added. See the note at
29+
; 'arc-exec, below.
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;
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(apply (parameterize ((current-namespace main-namespace))
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(namespace-variable-value (ac-global-name 'arc-name)))
33+
args)))
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((defarc name)
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(defarc name name))))
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@@ -424,8 +432,12 @@
424432
((eqv? a 't) (err "Can't rebind t"))
425433
((lex? a env) `(set! ,a zz))
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((ac-defined-var? a) `(,(ac-global-name a) zz))
427-
(#t `(namespace-set-variable-value! ',(ac-global-name a)
428-
zz)))
435+
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; The following has been changed from
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; 'namespace-set-variable-value! to 'set!. See
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; the note at 'arc-exec, below.
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;
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(#t `(set! ,(ac-global-name a) zz)))
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'zz))
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(err "First arg to set must be a symbol" a)))
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@@ -475,7 +487,12 @@
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((and (pair? fn) (eqv? (car fn) 'fn))
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`(,(ac fn env) ,@(ac-args (cadr fn) args env)))
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((and (ar-bflag 'direct-calls) (symbol? fn) (not (lex? fn env)) (bound? fn)
478-
(procedure? (namespace-variable-value (ac-global-name fn))))
490+
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; The following has been changed from using
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; 'namespace-variable-value to using 'arc-eval. See
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; the note at 'arc-exec, below.
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;
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(procedure? (arc-eval fn)))
479496
(ac-global-call fn args env))
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(#t
481498
`((ar-coerce ,(ac fn env) 'fn)
@@ -490,9 +507,12 @@
490507

491508
(define (ac-macro? fn)
492509
(if (symbol? fn)
493-
(let ((v (namespace-variable-value (ac-global-name fn)
494-
#t
495-
(lambda () #f))))
510+
511+
; The following has been changed from using
512+
; 'namespace-variable-value to using 'bound? and 'arc-eval. See
513+
; the note at 'arc-exec, below.
514+
;
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(let ((v (and (bound? fn) (arc-eval fn))))
496516
(if (and v
497517
(ar-tagged? v)
498518
(eq? (ar-type v) 'mac))
@@ -1128,8 +1148,39 @@
11281148
; top level read-eval-print
11291149
; tle kept as a way to get a break loop when a scheme err
11301150

1151+
; To make namespace and module handling more seamless (see
1152+
; lib/ns.arc), we use Racket's 'set! even for undefined variables,
1153+
; rather than using 'namespace-set-variable-value! for all Arc
1154+
; globals. This makes it possible to parameterize the value of
1155+
; 'current-namespace without getting odd behavior, and it makes it
1156+
; possible to assign to imported module variables and use
1157+
; assignment-aware syntax transformers (particularly those made with
1158+
; Racket's 'make-set!-transformer and 'make-rename-transformer).
1159+
;
1160+
; However, by default 'set! is disallowed when the variable is
1161+
; undefined, and we have to use the 'compile-allow-set!-undefined
1162+
; parameter to go against that default. Rather than sprinkling
1163+
; (parameterize ...) forms all over the code and trying to keep them
1164+
; in sync, we put them all in this function, and we use this function
1165+
; instead of 'eval when executing the output of 'ac.
1166+
;
1167+
; In the same spirit, several other uses of 'namespace-variable-value
1168+
; and 'namespace-set-variable-value! have been changed to more direct
1169+
; versions ((set! ...) forms and direct variable references) or less
1170+
; direct versions (uses of full 'arc-eval) depending on how their
1171+
; behavior should change when a module import or syntax obstructs the
1172+
; original meaning of the variable. Some have instead been kept
1173+
; around, but surrounded by (parameterize ...) forms so they're tied
1174+
; the main namespace. Another utility changed in this spirit is
1175+
; 'bound?, which should now be able to see variables which are bound
1176+
; as Racket syntax.
1177+
;
1178+
(define (arc-exec racket-expr)
1179+
(eval (parameterize ((compile-allow-set!-undefined #t))
1180+
(compile racket-expr))))
1181+
11311182
(define (arc-eval expr)
1132-
(eval (ac expr '())))
1183+
(arc-exec (ac expr '())))
11331184

11341185
(define (tle)
11351186
(display "Arc> ")
@@ -1167,8 +1218,13 @@
11671218
(when interactive?
11681219
(arc-write (ac-denil val))
11691220
(newline))
1170-
(namespace-set-variable-value! '_that val)
1171-
(namespace-set-variable-value! '_thatexpr expr)
1221+
1222+
; The following 'parameterize has been added. See the
1223+
; note at 'arc-exec, above.
1224+
;
1225+
(parameterize ((current-namespace main-namespace))
1226+
(namespace-set-variable-value! '_that val)
1227+
(namespace-set-variable-value! '_thatexpr expr))
11721228
(tl2 interactive?)))))))
11731229

11741230
(define (aload1 p)
@@ -1204,7 +1260,7 @@
12041260
(if (eof-object? x)
12051261
#t
12061262
(let ((scm (ac x '())))
1207-
(eval scm)
1263+
(arc-exec scm)
12081264
(pretty-print scm op)
12091265
(newline op)
12101266
(newline op)
@@ -1227,7 +1283,7 @@
12271283
(xdef macex1 (lambda (e) (ac-macex (ac-denil e) 'once)))
12281284

12291285
(xdef eval (lambda (e)
1230-
(eval (ac (ac-denil e) '()))))
1286+
(arc-eval (ac-denil e))))
12311287

12321288
; If an err occurs in an on-err expr, no val is returned and code
12331289
; after it doesn't get executed. Not quite what I had in mind.
@@ -1310,12 +1366,11 @@
13101366
(define (nth-set! lst n val)
13111367
(x-set-car! (list-tail lst n) val))
13121368

1313-
; rewrite to pass a (true) gensym instead of #f in case var bound to #f
1314-
13151369
(define (bound? arcname)
1316-
(namespace-variable-value (ac-global-name arcname)
1317-
#t
1318-
(lambda () #f)))
1370+
(with-handlers ((exn:fail:syntax? (lambda (e) #t))
1371+
(exn:fail:contract:variable? (lambda (e) #f)))
1372+
(namespace-variable-value (ac-global-name arcname))
1373+
#t))
13191374

13201375
(xdef bound (lambda (x) (tnil (bound? x))))
13211376

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