(* Title: HOL/Boogie/Examples/Boogie_Max.thy
Author: Sascha Boehme, TU Muenchen
*)
header {* Boogie example: get the greatest element of a list *}
theory Boogie_Max
imports Boogie
begin
text {*
We prove correct the verification condition generated from the following
Boogie code:
\begin{verbatim}
procedure max(array : [int]int, length : int)
returns (max : int);
requires (0 < length);
ensures (forall i: int :: 0 <= i && i < length ==> array[i] <= max);
ensures (exists i: int :: 0 <= i && i < length ==> array[i] == max);
implementation max(array : [int]int, length : int) returns (max : int)
{
var p : int, k : int;
max := array[0];
k := 0;
p := 1;
while (p < length)
invariant (forall i: int :: 0 <= i && i < p ==> array[i] <= max);
invariant (array[k] == max);
{
if (array[p] > max) { max := array[p]; k := p; }
p := p + 1;
}
}
\end{verbatim}
*}
boogie_open "~~/src/HOL/Boogie/Examples/Boogie_Max"
declare [[smt_certificates="~~/src/HOL/Boogie/Examples/Boogie_Max.certs"]]
declare [[smt_record=false]]
boogie_vc max
using [[z3_proofs=true]]
by boogie
boogie_end
end