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// Note: To prove termination of calls, methods need
// a termination measure, but Dafny does not yet support
// termination measures for methods (but it will in
// the foreseeable future).
// Spec# and Boogie and Chalice: The program will be
// the same, except that these languages do not check
// for any kind of termination.
class Benchmark1 {
method Add(x: int, y: int) returns (r: int)
ensures r == x+y;
{
r := x;
if (y < 0) {
var n := y;
while (n != 0)
invariant r == x+y-n && 0 <= -n;
decreases -n;
{
r := r - 1;
n := n + 1;
}
} else {
var n := y;
while (n != 0)
invariant r == x+y-n && 0 <= n;
decreases n;
{
r := r + 1;
n := n - 1;
}
}
}
method Mul(x: int, y: int) returns (r: int)
ensures r == x*y;
decreases x < 0, x;
{
if (x == 0) {
r := 0;
} else if (x < 0) {
call r := Mul(-x, y);
r := -r;
} else {
call r := Mul(x-1, y);
call r := Add(r, y);
}
}
}
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