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|
// RUN: %dafny /compile:0 /print:"%t.print" /dprint:"%t.dprint" "%s" > "%t"
// RUN: %diff "%s.expect" "%t"
// regular modifies sanity test:
method Testing1(a: array<int>)
requires a != null && a.Length > 0;
{
a[0] := 0; // ERROR
}
// array inside while loop, without explict modifies clause:
method Testing2(a: array<int>)
requires a != null && a.Length > 0;
{
var i := 0;
while(i < 10)
invariant 0 <= i <= 10;
{
a[0] := i; // ERROR
i := i + 1;
}
}
// array inside while loop, without explict modifies clause:
method Testing2A(a: array<int>)
requires a != null && a.Length > 0;
modifies a;
{
var i := 0;
while(i < 10)
invariant 0 <= i <= 10;
{
// now there is no problem.
a[0] := i;
i := i + 1;
}
}
// array inside while loop, with explict modifies clause:
method Testing3(a: array<int>)
requires a != null && a.Length > 0;
{
var i := 0;
while(i < 10)
invariant 0 <= i <= 10;
modifies {};
{
a[0] := i; // ERROR
i := i + 1;
}
}
// modifies restricts:
method Testing4(a: array<int>)
requires a != null && a.Length > 0;
modifies a;
{
var i := 0;
while(i < 10)
invariant 0 <= i <= 10;
modifies {};
{
a[0] := i; // ERROR
i := i + 1;
}
// should be ok.
a[0] := 1;
}
// modifies not a subset:
method Testing5(a: array<int>)
requires a != null && a.Length > 0;
modifies {};
{
var i := 0;
while(i < 10) // ERROR
invariant 0 <= i <= 10;
modifies a;
{
a[0] := i;
i := i + 1;
}
}
// modifies is a subset, but modifications occur outside:
method Testing6(a: array<int>, b: array<int>)
requires a != null && a.Length > 0;
requires b != null && b.Length > 0;
modifies a, b;
{
var i := 0;
while(i < 10)
invariant 0 <= i <= 10;
modifies a;
{
// cool.
a[0] := i;
// not cool.
b[0] := i; // ERROR
i := i + 1;
}
}
// heap outside modifies is actually preserved:
method Testing7(a: array<int>, b: array<int>)
requires a != null && a.Length > 0;
requires b != null && b.Length > 0;
requires a != b;
modifies a, b;
{
var i := 0;
b[0] := 4;
while(i < 10)
invariant 0 <= i <= 10;
modifies a;
{
// still good.
a[0] := i;
i := i + 1;
}
// this is new, and good:
assert b[0] == 4;
}
// modifies actually restrict frame when nested:
method Testing8(a: array<int>, b: array<int>, c: array<int>)
requires a != null && a.Length > 0;
requires b != null && b.Length > 0;
requires c != null && c.Length > 0;
requires a != b && b != c && c != a;
modifies a, b, c;
{
var i := 0;
b[0] := 4;
while(i < 10)
invariant 0 <= i <= 10;
modifies a, b;
{
var j := 0;
while(j < 10)
invariant 0 <= j <= 10;
modifies a;
{
// happy:
a[0] := j;
// not happy:
b[0] := i; // ERROR
j := j + 1;
}
i := i + 1;
}
c[0] := 1;
}
// heap outside modifies preserved when nested:
method Testing9(a: array<int>, b: array<int>, c: array<int>)
requires a != null && a.Length > 0;
requires b != null && b.Length > 0;
requires c != null && c.Length > 0;
requires a != b && b != c && c != a;
modifies a, b, c;
{
var i := 0;
b[0] := 4;
while(i < 10)
invariant 0 <= i <= 10;
modifies a, b;
{
var j := 0;
b[0] := i;
while(j < 10)
invariant 0 <= j <= 10;
modifies a;
{
a[0] := j;
j := j + 1;
}
assert b[0] == i;
i := i + 1;
}
c[0] := 1;
}
// allocation, fresh tests:
// allocated things not automatically in modifies of loops:
method Testing10(a: array<int>)
requires a != null && a.Length > 0;
modifies a;
{
var i := 0;
var arr := new int[1];
arr[0] := 1; // good, even though not in method modifies.
while(i < 10)
invariant 0 <= i <= 10;
modifies a;
{
arr[0] := 1; // ERROR
i := i + 1;
}
}
// unless no modifies given, in which case the context is used:
method Testing10a(a: array<int>)
requires a != null && a.Length > 0;
modifies a;
{
var i := 0;
var arr := new int[1];
arr[0] := 1; // still good.
while(i < 10)
invariant 0 <= i <= 10;
{
arr[0] := 1; // no modifies, so allowed to touch arr.
i := i + 1;
}
}
// loop inherits modifies clause of enclosing loop, not method.
method Testing10b(a: array<int>, b: array<int>)
requires a != null && a.Length > 0;
requires b != null && b.Length > 0;
requires a != b;
modifies a,b;
{
b[0] := 4;
var j := 0;
while (j < 10)
modifies a;
{
var i := 1;
while (i < 10)
// note: no explicit modifies clause
{
a[0] := 1;
i := i + 1;
}
assert b[0] == 4; // should be fine.
j := j + 1;
}
}
// arr still accessible after loop that can't touch it.
method Testing11()
{
var i := 0;
var arr := new int[1];
while(i < 10)
invariant 0 <= i <= 10;
modifies {};
{
arr := new int[1];
arr[0] := 1;
var j := 0;
while(j < 10)
invariant 0 <= j <= 10;
modifies {};
{
// can't touch arr in here.
j := j + 1;
}
arr[0] := 2;
i := i + 1;
}
}
// allocation inside a loop is still ok:
method Testing11a(a: array<int>)
requires a != null && a.Length > 0;
modifies a;
{
var i := 0;
while(i < 10)
invariant 0 <= i <= 10;
modifies a;
{
var arr := new int[1];
arr[0] := 1; // can modify arr, even though it
// is not in modifies because it is fresh.
var j := 0;
while(j < 10)
invariant 0 <= j <= 10;
modifies a;
{
arr[0] := 3; // ERROR: can't touch arr, as allocated before modifies captured.
j := j + 1;
}
i := i + 1;
}
}
class Elem
{
var i: int;
}
// capture of modifies clause at beginning of loop:
method Testing12(a: Elem, b: Elem, c: Elem)
requires a != null && b != null && c != null;
requires a != b && b != c && c != a; // all different.
modifies a, b, c;
{
var i := 0;
var S := {a, b, c};
// S "captured" here for purposes of modifies clause.
while(S != {})
modifies S;
decreases S;
{
var j :| j in S;
// these still good, even though S shrinks to not include them.
a.i := i;
b.i := i;
c.i := i;
S := S - {j};
i := i + 1;
}
}
|
