gallery: simple verification exercises

examples/swap.mlw

+
+module Swap
+
+  use import int.Int
+  use import ref.Ref
+
+  let swap (a b: ref int) : unit
+    writes  { a, b }
+    ensures { !a = old !b /\ !b = old !a }
+  =
+    a := !a + !b;
+    b := !a - !b;
+    a := !a - !b
+
+end

examples/swap/why3session.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE why3session PUBLIC "-//Why3//proof session v5//EN"
+"http://why3.lri.fr/why3session.dtd">
+<why3session shape_version="4">
+<prover id="0" name="Alt-Ergo" version="0.99.1" timelimit="6" memlimit="1000"/>
+<file name="../swap.mlw" expanded="true">
+<theory name="Swap" sum="5488140ff7d3e24ad9f42a3b571a28a3" expanded="true">
+ <goal name="WP_parameter swap" expl="VC for swap" expanded="true">
+ <proof prover="0"><result status="valid" time="0.01" steps="3"/></proof>
+ </goal>
+</theory>
+</file>
+</why3session>