From 4db1e51ab71e05bce1119c2c354b67c63fe6ae57 Mon Sep 17 00:00:00 2001
From: Correl Roush <correl@gmail.com>
Date: Tue, 13 May 2014 19:31:15 -0400
Subject: [PATCH] fixup state transformer monad

---
 src/state-transformer.lfe                  | 10 ++++++----
 test/unit/unit-state-transformer-tests.lfe | 15 +++++++++++----
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/src/state-transformer.lfe b/src/state-transformer.lfe
index 7f83927..2f1659b 100644
--- a/src/state-transformer.lfe
+++ b/src/state-transformer.lfe
@@ -16,10 +16,10 @@
    (lambda (_) (call inner-monad 'fail reason))))
 
 (defun >>=
-  ((x f (tuple 'maybe-transformer inner-monad))
+  ((x f (tuple 'state-transformer inner-monad))
    (lambda (s)
      (call inner-monad '>>=
-       (funcall x f)
+       (funcall x s)
        (match-lambda (((tuple x1 s1)) (funcall (funcall f x1) s1)))))))
 
 (defun get (_)
@@ -39,13 +39,15 @@
   ((m s (tuple 'state-transformer inner-monad))
    (call inner-monad '>>=
      (funcall m s)
-     (match-lambda (((tuple x s1)) x)))))
+     (match-lambda (((tuple x s1))
+                    (call inner-monad 'return x))))))
 
 (defun exec
   ((m s (tuple 'state-transformer inner-monad))
    (call inner-monad '>>=
      (funcall m s)
-     (match-lambda (((tuple x s1)) s1)))))
+     (match-lambda (((tuple x s1))
+                    (call inner-monad 'return s1))))))
 
 (defun run
   ((m s (tuple 'state-transformer inner-monad))
diff --git a/test/unit/unit-state-transformer-tests.lfe b/test/unit/unit-state-transformer-tests.lfe
index 859c3c9..abf65be 100644
--- a/test/unit/unit-state-transformer-tests.lfe
+++ b/test/unit/unit-state-transformer-tests.lfe
@@ -8,9 +8,6 @@
 (include-lib "deps/lfeunit/include/lfeunit-macros.lfe")
 (include-lib "include/monads.lfe")
 
-(deftestskip foo
-  (is 'false))
-
 (deftest eval
   (is-equal 5
             (let* ((m (: state-transformer new 'identity-monad))
@@ -23,7 +20,7 @@
                    (mval (call m 'return 5)))
               (call m 'exec mval 'foo))))
 
-(deftest exec-double
+(deftest exec-modify
   (is-equal 10
             (let ((m (: state-transformer new 'identity-monad)))
               (call m 'exec
@@ -31,6 +28,16 @@
                       (call m 'modify (lambda (x) (* x 2))))
                 5))))
 
+(deftest exec-modify-multiple
+  (is-equal 30
+            (let ((m (: state-transformer new 'identity-monad)))
+              (call m 'exec
+                (do-m m
+                      (call m 'modify (lambda (x) (+ x 5)))
+                      (call m 'modify (lambda (x) (* x 2)))
+                      (call m 'return 123))
+                10))))
+
 (deftest exec-fail
   (is-throw #(error value)
             (let ((m (: state-transformer new 'identity-monad)))