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Diffstat (limited to '')
-rw-r--r-- | examples/state-minimal.scm | 54 |
1 files changed, 0 insertions, 54 deletions
diff --git a/examples/state-minimal.scm b/examples/state-minimal.scm deleted file mode 100644 index 8a88ac6..0000000 --- a/examples/state-minimal.scm +++ /dev/null @@ -1,54 +0,0 @@ -(use-modules (ice-9 curried-definitions) - (ice-9 match)) - -;;; This is a minimal implementation of the state monad. -;;; It is incompatible with the rest of my monad system, -;;; since everything either has type <pair> or <procedure>. -;;; But it should work as a nice base for the actual -;;; implementation. - -;;; This implementation works, as far as I can tell, exactly -;;; like the Haskell version (of MonadState). But obviously -;;; without all the nice syntax. - -;;; Anything that takes an st-list and returns an st-list is -;;; considered a State value. -;;; An st-list is a list where the car is the last returned -;;; value, and the cadr is the "state". - -;; newtype State = st-list -> st-list - -;; State -(define ((get) st-list) - "Sets the return value to the state value" - (match st-list - ((v st) - (list st st)))) - -;; v -> State -(define ((put v) st-list) - "Sets the state value to v, sets the return value to ()" - (list '() v)) - -;; State -> (v -> State) -> State -(define ((bind st-proc proc) st-list) - (let ((new-st-list (st-proc st-list))) - (match new-st-list - ((v _) - ((proc v) new-st-list))))) - -;; State -> State -> State -(define ((then st-proc-1 st-proc-b) st-list-a) - (let ((st-list-b (st-proc-1 st-list-a))) - (st-proc-b st-list-b))) - -;; v -> State -(define ((return v) st-list) - "Sets the return value to v" - (cons v (cdr st-list))) - -;; State -> v -> (r v) -(define (run-state st-proc init) - "Exec state with init as starting state value" - (st-proc (list init init))) - |