Add num.sign getter.

tests/corelib/num_sign_test.dart

+// Copyright (c) 2013, 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.
+// Test num.clamp.
+
+import "package:expect/expect.dart";
+
+// Pedestrian implementation of sign, following its specification directly.
+num sign(num value) {
+  if (value is int) {
+    if (value < 0) return -1;
+    if (value > 0) return 1;
+    return 0;
+  }
+  if (value.isNaN) return value;
+  if (value == 0.0) return value;
+  if (value > 0.0) return 1.0;
+  return -1.0;
+}
+
+var numbers = [
+  // Integers
+  0,
+  1,
+  2,
+  0x7f,                     // ~7 bits
+  0x80,
+  0xff,                     // ~8 bits
+  0x100,
+  0xffff,                   // ~16 bits
+  0x10000,
+  0x3fffffff,               // ~30 bits (max positive 32-bit tagged smi)
+  0x40000000,
+  0x40000001,
+  0x7fffffff,               // ~31 bits
+  0x80000000,
+  0x80000001,
+  0xfffffffff,              // ~32 bits
+  0x100000000,
+  0x100000001,
+  0x10000000000000,         // ~53 bits
+  0x10000000000001,
+  0x1fffffffffffff,
+  0x20000000000000,
+  0x20000000000001,         // first integer not representable as double.
+  0x20000000000002,
+  0x7fffffffffffffff,       // ~63 bits
+  0x8000000000000000,
+  0x8000000000000001,
+  0xffffffffffffffff,       // ~64 bits
+  0x10000000000000000,
+  0x10000000000000001,
+  // Integers around the max-double range (2^1024, ~1025 bits).
+  0xfffffffffffff800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000,
+  0xfffffffffffffc00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000,
+  0x10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000,
+  // Doubles.
+  0.0,
+  5e-324,                   // min positive
+  2.225073858507201e-308,   // max denormal
+  2.2250738585072014e-308,  // min normal
+  0.49999999999999994,      // ~0.5
+  0.5,
+  0.5000000000000001,
+  0.9999999999999999,       // ~1.0
+  1.0,
+  1.0000000000000002,
+  4294967295.0,             // ~32 bits
+  4294967296.0,
+  4503599627370495.5,       // max fractional
+  4503599627370497.0,
+  9007199254740991.0,
+  9007199254740992.0,       // max exact (+1 is not a double)
+  1.7976931348623157e+308,  // max finite double
+  1.0 / 0.0,                // Infinity
+  0.0 / 0.0,                // NaN
+];
+
+main() {
+  for (num number in numbers) {
+    test(number);
+    test(-number);
+  }
+}
+
+void test(number) {
+  num expectSign = sign(number);
+  num actualSign = number.sign;
+  if (expectSign.isNaN) {
+    Expect.isTrue(actualSign.isNaN, "$number: $actualSign != NaN");
+  } else {
+    if (number is int) {
+      Expect.isTrue(actualSign is int, "$number.sign is int");
+    } else {
+      Expect.isTrue(actualSign is double, "$number.sign is double");
+    }
+    Expect.equals(expectSign, actualSign, "$number");
+    Expect.equals(number.isNegative, actualSign.isNegative, "$number:negative");
+    var renumber = actualSign * number.abs();
+    Expect.equals(number, renumber, "$number (sign*abs)");
+    if (number is int) {
+      Expect.isTrue(renumber is int, "$number (sign*abs) is int");
+    } else {
+      Expect.isTrue(renumber is double, "$number (sign*abs) is double");
+    }
+  }
+}