Data commit

Task/Conditional-structures/Isabelle/conditional-structures.isabelle

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+theory Scratch
+  imports Main
+begin
+
+text‹if-then-else›
+lemma "(if True then 42 else 0) = 42" by simp
+
+text‹case statement with pattern matching, which evaluates to the True-case›
+lemma "case [42] of
+         Nil  ⇒ False
+       | [x]  ⇒ True
+       | x#xs ⇒ False" by simp
+
+text‹Loops are implemented via recursive functions›
+fun recurse :: "nat ⇒ nat" where
+  "recurse 0 = 0"
+| "recurse (Suc n) = recurse n"
+
+text‹The function always returns zero.›
+lemma "recurse n = 0" by(induction n) simp+
+
+end