From b282f1a92137e2104b96186d05ff6e543eafdf2a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20H=C3=B6rnquist?= <hugo@hornquist.se>
Date: Tue, 13 Nov 2018 00:18:31 +0100
Subject: run-state, >>=, and >> now correctly defined for <state>.

---
 control/monad/state.scm | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/control/monad/state.scm b/control/monad/state.scm
index a8e7775..3ebdcc6 100644
--- a/control/monad/state.scm
+++ b/control/monad/state.scm
@@ -29,16 +29,18 @@
   (make <state> #:proc proc))
 
 (define-method (>>= (st <state>) f)
-  (lambda (st-list)
-    (let ((new-st-list ((proc st) st-list)))
-      (match new-st-list
-        ((v _)
-         ((proc (f v)) new-st-list))))))
+  (make-state
+   (lambda (st-list)
+     (let ((new-st-list ((proc st) st-list)))
+       (match new-st-list
+         ((v _)
+          ((proc (f v)) new-st-list)))))))
 
 (define-method (>> (a <state>) (b <state>))
-  (lambda (st-list-a)
-    (let ((st-list-b ((proc a) st-list-a)))
-      ((proc b) st-list-b))))
+  (make-state
+   (lambda (st-list-a)
+     (let ((st-list-b ((proc a) st-list-a)))
+       ((proc b) st-list-b)))))
 
 (define-syntax define-stateful
   (syntax-rules ()
@@ -61,7 +63,7 @@
   "Sets st to v."
   (list '() v))
 
-(define-method (run-state st-proc init)
+(define-method (run-state (st <state>) init)
   "Exec state with init as starting state value and st."
-  (st-proc (list init init)))
+  ((proc st) (list init init)))
 
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