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Diffstat (limited to 'Test/hofs/Twice.dfy')
-rw-r--r-- | Test/hofs/Twice.dfy | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/Test/hofs/Twice.dfy b/Test/hofs/Twice.dfy new file mode 100644 index 00000000..add7e83c --- /dev/null +++ b/Test/hofs/Twice.dfy @@ -0,0 +1,38 @@ +// RUN: %dafny /print:"%t.print" "%s" > "%t" +// RUN: %diff "%s.expect" "%t" + +function method Twice(f : A -> A): A -> A +{ + x requires f.requires(x) && f.requires(f(x)) + reads f.reads(x) reads if f.requires(x) then f.reads(f(x)) else {} + => f(f(x)) +} + +method Simple() { + assert Twice(x => x + 1)(0) == 2; + assert Twice(Twice(x => x + 1))(0) == 4; + + // why does these fail? need requires/reads for literals? + // assert Twice(Twice)(x => x + 1)(0) == 4; + // assert Twice(Twice)(Twice)(x => x + 1)(0) == 16; +} + +method WithReads() { + var a : array<int> := new int[1]; + a[0] := 1; + var f := x reads a => x + a[0]; + assert Twice(f)(0) == 2; + a[0] := 2; + assert Twice(f)(0) == 4; + assert Twice(f)(0) == 2; // should fail + assert false; // should fail +} + + +function method Twice_bad(f : A -> A): A -> A +{ + x requires f.requires(x) && f.requires(f(x)) + reads f.reads(x) + f.reads(f(x)) + => f(f(x)) +} + |