| // Copyright (c) 2016, 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"; |
| |
| bool testAssociativity(Function f) { |
| // Example from https://en.wikipedia.org/wiki/Floating_point |
| // Test that (a + b) + c == a + (b + c). |
| double a = f(1234.567); // Chop literals. |
| double b = f(45.67834); |
| double c = f(0.0004); |
| double x = (a + b) + c; // Chop result of multiplication or division only. |
| double y = a + (b + c); |
| print("x: $x"); |
| print("y: $y"); |
| return x == y; |
| } |
| |
| bool testDistributivity(Function f) { |
| // Example from https://en.wikipedia.org/wiki/Floating_point |
| // Test that (a + b)*c == a*c + b*c. |
| double a = f(1234.567); // Chop literals. |
| double b = f(1.234567); |
| double c = f(3.333333); |
| double x = f((a + b)*c); // Chop result of multiplication. |
| double y = f(a*c) + f(b*c); |
| print("x: $x"); |
| print("y: $y"); |
| return x == y; |
| } |
| |
| // Simulate precision checking with assert. |
| assertP(double d) { |
| assert(d == d.p); |
| } |
| |
| bool assertionsEnabled() { |
| try { |
| assert(false); |
| return false; |
| } on AssertionError catch (e) { |
| return true; |
| } |
| return false; |
| } |
| |
| main() { |
| // The getter p keeps only 20 (by default) bits after the decimal point. |
| Expect.equals(0.0, 0.0.p); // 0.0 has no 1-bit after the decimal point. |
| Expect.equals(1.5, 1.5.p); // 1.5 has a single 1-bit after the decimal point. |
| Expect.notEquals(1.1, 1.1.p); // 1.1 has many 1-bits after the decimal point. |
| Expect.notEquals(1/3, (1/3).p); // 0.33333333... ditto. |
| |
| Expect.equals(1.1 + 1/3, 1/3 + 1.1); // Test addition commutativity. |
| Expect.equals(1.1.p + (1/3).p, (1/3).p + 1.1.p); |
| Expect.equals(1.1 * 1/3, 1/3 * 1.1); // Test multiplication commutativity. |
| Expect.equals(1.1.p * (1/3).p, (1/3).p * 1.1.p); |
| |
| print("Without chopping fractional bits:"); |
| Expect.isFalse(testAssociativity((x) => x)); |
| Expect.isFalse(testDistributivity((x) => x)); |
| print("With chopping fractional bits:"); |
| Expect.isTrue(testAssociativity((x) => x.p)); |
| Expect.isTrue(testDistributivity((x) => x.p)); |
| |
| // Check that p works with NaN and Infinity. |
| Expect.isTrue(double.NAN.p.isNaN); |
| Expect.isTrue(double.INFINITY.p.isInfinite); |
| Expect.isFalse(double.INFINITY.p.isNegative); |
| Expect.isTrue(double.NEGATIVE_INFINITY.p.isInfinite); |
| Expect.isTrue(double.NEGATIVE_INFINITY.p.isNegative); |
| |
| // Check use of assert to verify precision. |
| if (assertionsEnabled()) { |
| assertP(1.5); |
| assertP(1.1.p); |
| Expect.throws(() => assertP(1.1), (e) => e is AssertionError); |
| assertP(1.23456789.p); |
| Expect.throws(() => assertP(1.23456789), (e) => e is AssertionError); |
| } |
| } |