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|
// RUN: %dafny /dprint:- /env:0 "%s" > "%t"
// RUN: %diff "%s.expect" "%t"
predicate P(n: int)
{
n % 2 == 0
}
predicate R(r: real)
{
0.0 <= r
}
method M0()
{
if x :| P(x) {
var y := x + 3;
}
}
method M1()
{
if x: int :| P(x) {
}
}
method M2()
{
var x := true;
if x, y :| P(x) && R(y) { // this declares a new 'x'
var z := x + 12;
}
x := x && false;
}
method M3()
{
var x := true;
if x: int, y :| P(x) && R(y) {
var z := x + y.Trunc;
var w := real(x) + y;
}
}
method M4()
{
if x, y: real :| P(x) && R(y) {
}
}
method M5()
{
if x: int, y: real :| P(x) && R(y) {
}
}
method M6()
{
if x {:myattribute x, "hello"} :| P(x) {
}
if x, y {:myattribute y, "sveika"} :| P(x) && R(y) {
}
if x: int {:myattribute x, "chello"} :| P(x) {
}
if x {:myattribute x, "hola"} {:yourattribute x + x, "hej"} :| P(x) {
}
}
ghost method M7() returns (z: real, w: real)
ensures -2.0 <= z
ensures z == w // error: does not hold
{
var k;
if x :| P(x) {
k, z := 4, 18.0;
} else if * {
z := z + -z;
} else if y :| R(y) {
z := y;
} else if y :| P(y) {
k := y;
} else {
z :| R(z);
}
if P(k) {
z := 18.0;
}
}
ghost method M8(m: int, n: int)
requires forall y :: m <= y < n ==> P(y)
{
var t := -1;
var u;
if y :| m <= y < n && P(y) {
u := y;
if * {
t := n - y;
} else if * {
t := y - m;
} else if P(y) {
t := 8;
} else {
t := -100; // will never happen
}
}
if t < 0 && m < n {
assert P(m) && !P(m);
assert false;
}
assert t < 0 ==> n <= m;
}
method P0(m: int, n: int)
requires m < n
{
ghost var even, alsoEven := 4, 8;
if {
case x :| P(x) =>
even := x;
case x: int :| P(x) =>
even := x;
case x, y :| P(x) && R(y) =>
even, alsoEven := x, y.Trunc; // this assigns to 'alsoEven' a possibly odd number
case x: int, y :| P(x) && R(y) =>
even := x;
case m < n => // just to be different
case x, y: real :| P(x) && R(y) =>
even := x;
case x: int, y: real :| P(x) && R(y) =>
even := x;
}
assert P(even);
assert P(alsoEven); // error: may not hold
}
method P1(m: int, n: int)
{
if { // error: missing case
case x :| m <= x < n && P(x) =>
}
}
method P2(m: int, n: int)
requires forall y :: m <= y < n ==> P(y)
{
if { // error: missing case
case x :| m <= x < n && P(x) =>
}
}
method P3(m: int, n: int)
requires m < n && forall y :: m <= y < n ==> P(y)
{
assert P(m); // lemma that proves that the following 'if' covers all possibilities
if {
case x :| m <= x < n && P(x) =>
}
}
|
