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| author | Hugo Hörnquist <hugo@lysator.liu.se> | 2018-11-16 00:08:53 +0100 |
|---|---|---|
| committer | Hugo Hörnquist <hugo@lysator.liu.se> | 2018-11-16 00:08:53 +0100 |
| commit | f482ecdb4ec3cd0ecf4698a2917e971aab31f2ac (patch) | |
| tree | 8448549ee60f4d6d148c859dc091fc93a791025d | |
| parent | Made do notation support pattern matching. (diff) | |
| download | scheme-monad-f482ecdb4ec3cd0ecf4698a2917e971aab31f2ac.tar.gz scheme-monad-f482ecdb4ec3cd0ecf4698a2917e971aab31f2ac.tar.xz | |
Add modify to (control monad state).
| -rw-r--r-- | control/monad/state.scm | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/control/monad/state.scm b/control/monad/state.scm index 72a3041..603e387 100644 --- a/control/monad/state.scm +++ b/control/monad/state.scm @@ -2,8 +2,8 @@ #:use-module (oop goops) #:use-module (ice-9 match) #:use-module (control monad) - #:export (return-state run-state get put) #:re-export (>>= >>)) + #:export (return-state run-state get put modify)) ;; Alternative implementation of get. @@ -66,6 +66,11 @@ "Sets st to v." (list '() v)) +(define-stateful ((modify proc) st-list) + (match st-list + ((r s) + (list '() (proc s))))) + (define-method (run-state (st <state>) init) "Exec state with init as starting state value and st." ((proc st) (list init init))) |