diff options
| -rw-r--r-- | doc/ref/api-control.texi | 9 | ||||
| -rw-r--r-- | module/ice-9/boot-9.scm | 14 |
2 files changed, 18 insertions, 5 deletions
diff --git a/doc/ref/api-control.texi b/doc/ref/api-control.texi index ca7ad4af6..6eac8726f 100644 --- a/doc/ref/api-control.texi +++ b/doc/ref/api-control.texi @@ -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{} diff --git a/module/ice-9/boot-9.scm b/module/ice-9/boot-9.scm index 1630461e1..94538fe58 100644 --- a/module/ice-9/boot-9.scm +++ b/module/ice-9/boot-9.scm @@ -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. ;;; |