blob: f907cea4303bf2f47533c281d7a032b39c91657d [file] [log] [blame]
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
import "package:expect/expect.dart";
// Dart test for deeply nested generic types.
/** A natural number aka Peano number. */
abstract class N {
N add1();
N sub1();
}
/** Zero element. */
class Z implements N {
Z();
N add1() {
return new S<Z>(this);
}
N sub1() {
throw "Error: sub1(0)";
}
}
/** Successor element. */
class S<K> implements N {
N before;
S(this.before);
N add1() {
return new S<S<K>>(this);
}
N sub1() {
// It would be super cool if this could be "new K()".
return before;
}
}
N NFromInt(int x) {
if (x == 0)
return new Z();
else
return NFromInt(x - 1).add1();
}
int IntFromN(N x) {
if (x is Z) return 0;
if (x is S) return IntFromN(x.sub1()) + 1;
throw "Error";
}
bool IsEven(N x) {
if (x is Z) return true;
if (x is S<Z>) return false;
if (x is S<S>) return IsEven(x.sub1().sub1());
throw "Error in IsEven";
}
main() {
Expect.isTrue(NFromInt(0) is Z);
Expect.isTrue(NFromInt(1) is S<Z>);
Expect.isTrue(NFromInt(2) is S<S<Z>>);
Expect.isTrue(NFromInt(3) is S<S<S<Z>>>);
Expect.isTrue(NFromInt(10) is S<S<S<S<S<S<S<S<S<S<Z>>>>>>>>>>);
// Negative tests.
Expect.isTrue(NFromInt(0) is! S);
Expect.isTrue(NFromInt(1) is! Z);
Expect.isTrue(NFromInt(1) is! S<S>);
Expect.isTrue(NFromInt(2) is! Z);
Expect.isTrue(NFromInt(2) is! S<Z>);
Expect.isTrue(NFromInt(2) is! S<S<S>>);
// Greater-than tests
Expect.isTrue(NFromInt(4) is S<S>); // 4 >= 2
Expect.isTrue(NFromInt(4) is S<S<S>>); // 4 >= 3
Expect.isTrue(NFromInt(4) is S<S<S<S>>>); // 4 >= 4
Expect.isTrue(NFromInt(4) is! S<S<S<S<S>>>>); // 4 < 5
Expect.isTrue(IsEven(NFromInt(0)));
Expect.isFalse(IsEven(NFromInt(1)));
Expect.isTrue(IsEven(NFromInt(2)));
Expect.isFalse(IsEven(NFromInt(3)));
Expect.isTrue(IsEven(NFromInt(4)));
Expect.equals(0, IntFromN(NFromInt(0)));
Expect.equals(1, IntFromN(NFromInt(1)));
Expect.equals(2, IntFromN(NFromInt(2)));
Expect.equals(50, IntFromN(NFromInt(50)));
}