commit 11fbff19acfdd65a206465af5fc68708dfc7b0c2
parent cedb9553137045409f3484b031f0d18cd7667839
Author: Georges Dupéron <georges.duperon@gmail.com>
Date: Mon, 19 Sep 2016 20:40:15 +0200
Make ~global-or and ~global-and always return booleans, so that the order of terms is not important.
Diffstat:
2 files changed, 13 insertions(+), 64 deletions(-)
diff --git a/private/global.rkt b/private/global.rkt
@@ -36,17 +36,19 @@
(~bind [clause-value (box-immutable v)]))]))
(define (aggregate-global-or . bs)
- (ormap unbox ;; remove the layer of protection
- (filter identity ;; remove failed bindings
- (flatten bs)))) ;; don't care about ellipsis nesting
+ (true? ;; force the result to be a boolean, the order of terms is unimportant
+ (ormap unbox ;; remove the layer of protection
+ (filter identity ;; remove failed bindings
+ (flatten bs))))) ;; don't care about ellipsis nesting
(define-eh-mixin-expander ~global-or
(make-~global #'aggregate-global-or #'#t))
(define (aggregate-global-and . bs)
- (andmap unbox ;; remove the layer of protection
- (cons (box-immutable 'none) ;; default value when no bindings matched
- (filter identity ;; remove failed bindings
- (flatten bs))))) ;; don't care about ellipsis nesting
+ (true? ;; force the result to be a boolean, the order of terms is unimportant
+ (andmap unbox ;; remove the layer of protection
+ (cons (box-immutable 'none) ;; default value when no bindings matched
+ (filter identity ;; remove failed bindings
+ (flatten bs)))))) ;; don't care about ellipsis nesting
(define-eh-mixin-expander ~global-and
(make-~global #'aggregate-global-and))
diff --git a/scribblings/extensible-parser-specifications.scrbl b/scribblings/extensible-parser-specifications.scrbl
@@ -251,31 +251,8 @@ the notion of order irrelevant.
If the @racket[valueᵢ] is omitted, @racket[#t] is used as a default.
- Since the aggregation function is @racket[or], the order in which values are
- aggregated means that within each @racket[valueᵢ] group, the first
- non-@racket[#f] value with a successful match of the corresponding
- @racket[_syntax-pattern]s is used. The first @racket[valueᵢ] for which that
- result is not @racket[#f], and with at least one successful match is then used.
-
- For example, the following code produces @racket['ya]:
-
- @racketblock[
- (syntax-parse #'(1 ya (2 #f 3) 4 yb (5 #f 6) yc 7)
- [(~no-order {~and x:id {~global-or [g (syntax-e #'x)]}}
- {~global-or [g (syntax-e #'y)] y:number}
- ({~global-or [g (syntax-e #'z)] (~and z (~or :number #f))}
- …)
- {~global-or [g (syntax-e #'w)] w:str})
- (attribute g)])]
-
- This is because the following call to @racket[or] is executed:
-
- @racketblock[
- (or 'ya 'yb 'yc (code:comment "matches for x")
- 1 4 7 (code:comment "matches for y")
- 2 #f 3 4 #f 6 (code:comment "matches for z")
- (code:comment "no matches for w"))]
-}
+ The result is always transformed into a boolean, so @racket[_attribute-name] is
+ always bound to either @racket[#t] or @racket[#f].}
@defform[(~global-and attribute-name+value #,ntax-pattern ...)
#:grammar
@@ -284,39 +261,9 @@ the notion of order irrelevant.
perform a global @racket[and] over all the values corresponding to successful
matches of a global pattern using the same @racket[#,tribute-name]. See above
for a description of how global operations work.
-
- Since the aggregation function is @racket[or], the order in which values are
- aggregated means that within each @racket[valueᵢ] group, the last value with a
- successful match of the corresponding @racket[_syntax-pattern]s is used. The
- last @racket[valueᵢ] with at least one successful match is then used. If any
- value within any @racket[valueᵢ] group is @racket[#f], then the
- @racket[_attribute-name] is bound to @racket[#f].
-
- @examples[
- #:eval (make-evaluator)
- #:once
- #:label "For example, the following code produces 6:"
- (syntax-parse #'(1 ya (2 3) 4 yb (5 6) yc 7)
- [(~no-order {~and x:id {~global-and [g (syntax-e #'x)]}}
- {~global-and [g (syntax-e #'y)] y:number}
- ({~global-and [g (syntax-e #'z)] (~and z :number)}
- …)
- {~global-and [g (syntax-e #'w)] w:str})
- (attribute g)])]
-
- This is because the following call to @racket[or] is executed:
- @racketblock[
- (and 'ya 'yb 'yc (code:comment "matches for x")
- 1 4 7 (code:comment "matches for y")
- 2 3 4 6 (code:comment "matches for z")
- (code:comment "no matches for w"))]
-
- This @tech{eh-mixin expander} is intended to be used to aggregate boolean
- values, so the order in which matches are taken into account should not be
- significant. To perform checks on the order in which matches appear within a
- @racket[~no-order] or @racket[~seq-no-order], see @racket[~order-point],
- @racket[order-point<] and @racket[order-point>].}
+ The result is always transformed into a boolean, so @racket[_attribute-name] is
+ always bound to either @racket[#t] or @racket[#f].}
@defform[(~global-counter attribute-name+value #,ntax-pattern ...)
#:grammar
