From 319643faf6baea1c44f68800cba1947799935d05 Mon Sep 17 00:00:00 2001
From: Edoardo La Greca
Date: Wed, 9 Jul 2025 22:35:50 +0200
Subject: add second exercise of lecture 5

---
 lec05/Calc.hs | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'lec05/Calc.hs')

diff --git a/lec05/Calc.hs b/lec05/Calc.hs
index 8051d76..cd6f408 100644
--- a/lec05/Calc.hs
+++ b/lec05/Calc.hs
@@ -1,6 +1,7 @@
 module Calc where
 
 import ExprT
+import Parser
 
 -- Exercise 1
 
@@ -8,3 +9,10 @@ eval :: ExprT -> Integer
 eval (Lit n) = n
 eval (Add l r) = eval l + eval r
 eval (Mul l r) = eval l * eval r
+
+-- Exercise 2
+
+evalStr :: String -> Maybe Integer
+evalStr s = case parseExp Lit Add Mul s of
+                 Nothing -> Nothing
+                 Just t -> Just (eval t)
-- 
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