From aebffcc1c786e8cea15fff6f324bf71fc37cbb37 Mon Sep 17 00:00:00 2001
From: Mart Lubbers
Date: Fri, 24 Apr 2015 09:10:46 +0200
Subject: updated practicum files

---
 files/practicum/StdStateMonad.icl | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
 create mode 100644 files/practicum/StdStateMonad.icl

(limited to 'files/practicum/StdStateMonad.icl')

diff --git a/files/practicum/StdStateMonad.icl b/files/practicum/StdStateMonad.icl
new file mode 100644
index 0000000..527ac5c
--- /dev/null
+++ b/files/practicum/StdStateMonad.icl
@@ -0,0 +1,16 @@
+implementation module StdStateMonad
+
+import StdMonad
+
+:: ST s a = ST (s -> (a, s))
+
+instance return (ST s) where return x     = ST (\w = (x, w))
+instance >>=    (ST s) where >>= (ST f) g = ST (\w = let (a, w1) = f w 
+                                                      in unST (g a) w1
+                                               )
+
+mkST :: (s -> (a,s)) -> ST s a
+mkST f = ST f
+
+unST :: (ST s a) -> s -> (a, s)
+unST (ST f) = f
-- 
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