From d2b12fdf5681a71f1f6a295b0591e4d8213fb41d Mon Sep 17 00:00:00 2001
From: Camil Staps
Date: Tue, 10 May 2016 21:12:44 +0200
Subject: Straightforward While lexer, parser and interpreter

---
 paper/While/Simple.icl | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 paper/While/Simple.icl

(limited to 'paper/While/Simple.icl')

diff --git a/paper/While/Simple.icl b/paper/While/Simple.icl
new file mode 100644
index 0000000..9138f1f
--- /dev/null
+++ b/paper/While/Simple.icl
@@ -0,0 +1,22 @@
+implementation module Simple
+
+import StdString
+
+import WhileCommon
+import Common
+
+instance toString Stm
+where
+	toString (Ass v a) = v <+ " := " <+ a
+	toString (If b s1 s2) = "if " <+ b <+ " then " <+ s1 <+ " else " <+ s2
+	toString (While b s) = "while " <+ b <+ " do " <+ s
+	toString Skip = "skip"
+	toString (Compose s1 s2) = s1 <+ "; " <+ s2
+
+instance run Stm
+where
+	run (Ass v e) st = eval e st >>= \r -> pure (\w -> if (w==v) (pure r) (st w))
+	run (If b s1 s2) st = eval b st >>= \r -> run (if r s1 s2) st
+	run w=:(While b s) st = eval b st >>= \r -> if r (run s st >>= \st` -> run w st`) (pure st)
+	run Skip st = pure st
+	run (Compose s1 s2) st = run s1 st >>= \st` -> run s2 st`
-- 
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