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faster (make-prompt-tag); default-prompt-tag is a parameter

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* module/ice-9/boot-9.scm (default-prompt-tag): Once parameters have
  booted, redefine as a parameter.
  (make-prompt-tag): Change from a gensym to a list.  Thanks to Mark
  Weaver for the suggestion.

* doc/ref/api-control.texi (Prompt Primitives): Update docs.
This commit is contained in:
Andy Wingo 2012-03-07 19:01:56 +01:00
parent a62b5c3d54
commit 283ab48d3f
2 changed files with 18 additions and 5 deletions
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9
doc/ref/api-control.texi
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@ -494,14 +494,17 @@ those passed to @code{abort-to-prompt}.
@end deffn
@deffn {Scheme Procedure} make-prompt-tag [stem]
Make a new prompt tag. Currently prompt tags are generated symbols.
This may change in some future Guile version.
Make a new prompt tag. A prompt tag is simply a unique object.
Currently, a prompt tag is a fresh pair. This may change in some future
Guile version.
@end deffn
@deffn {Scheme Procedure} default-prompt-tag
Return the default prompt tag. Having a distinguished default prompt
tag allows some useful prompt and abort idioms, discussed in the next
section.
section. Note that @code{default-prompt-tag} is actually a parameter,
and so may be dynamically rebound using @code{parameterize}.
@xref{Parameters}.
@end deffn
@deffn {Scheme Procedure} abort-to-prompt tag val1 val2 @dots{}

14
module/ice-9/boot-9.scm
View file

@ -51,10 +51,12 @@
(define make-prompt-tag
(lambda* (#:optional (stem "prompt"))
(gensym stem)))
;; The only property that prompt tags need have is uniqueness in the
;; sense of eq?. A one-element list will serve nicely.
(list stem)))
(define default-prompt-tag
;; not sure if we should expose this to the user as a fluid
;; Redefined later to be a parameter.
(let ((%default-prompt-tag (make-prompt-tag)))
(lambda ()
%default-prompt-tag)))
@ -1326,6 +1328,14 @@ VALUE."
;;; Once parameters have booted, define the default prompt tag as being
;;; a parameter.
;;;
(set! default-prompt-tag (make-parameter (default-prompt-tag)))
;;; Current ports as parameters.
;;;