Add documentation to dart:math pow function.

Add documentation to dart:math pow function.

Also add test, and modify implementation to match on the single case where it didn't.

BUG= http://dartdog.com/1952
R=floitsch@google.com

Committed: https://code.google.com/p/dart/source/detail?r=26347

[floitsch, 2013-08-19 14:47:31]

LGTM.
Please fix the CL title ("documentation").

Maybe consider splitting some of the +/-0 cases into two (especially if you have
"if the left argument is -0, ...").

https://codereview.chromium.org/22943005/diff/1/sdk/lib/math/math.dart
File sdk/lib/math/math.dart (right):

https://codereview.chromium.org/22943005/diff/1/sdk/lib/math/math.dart#newcod...
sdk/lib/math/math.dart:151: * - `pow(±0, y)` is infinite if y is negative. If
the first argument
there are two items +-0, y.
The next list-item seems more plausible too.

https://codereview.chromium.org/22943005/diff/1/sdk/lib/math/math.dart#newcod...
sdk/lib/math/math.dart:157: * - `pow(±0, −∞)` is positive infinity.
put the special cases first. Otherwise the generic "y" would already trigger.

[Lasse Reichstein Nielsen, 2013-08-19 15:51:31]

Seems the IEEE 754 spec itself is incomplete on pow, so I'll see if I fill in
the blanks (q.v., http://grouper.ieee.org/groups/754/email/msg03969.html) and
find a way to make a shorter summary.

[floitsch, 2013-08-20 10:56:23]

still LGTM.

https://codereview.chromium.org/22943005/diff/9001/runtime/lib/math_patch.dart
File runtime/lib/math_patch.dart (right):

https://codereview.chromium.org/22943005/diff/9001/runtime/lib/math_patch.dar...
runtime/lib/math_patch.dart:23: if (exponent is! num) {
remove the check.

https://codereview.chromium.org/22943005/diff/9001/sdk/lib/math/math.dart
File sdk/lib/math/math.dart (right):

https://codereview.chromium.org/22943005/diff/9001/sdk/lib/math/math.dart#new...
sdk/lib/math/math.dart:153: * - if `x` is Infinity and `y` is negative, the
result is 0.0.
strictly negative
although it is not necessary since the y==0 already handled that case.

https://codereview.chromium.org/22943005/diff/9001/sdk/lib/math/math.dart#new...
sdk/lib/math/math.dart:154: * - if `x` is Infinity and `y` is positive, the
result is Infinity.
strictly positive

https://codereview.chromium.org/22943005/diff/9001/tests/lib/math/double_pow_...
File tests/lib/math/double_pow_test.dart (right):

https://codereview.chromium.org/22943005/diff/9001/tests/lib/math/double_pow_...
tests/lib/math/double_pow_test.dart:56: main() {
add documentation edge-cases one by one (as written in the documentation).

[Lasse Reichstein Nielsen, 2013-08-20 12:18:11]

https://codereview.chromium.org/22943005/diff/9001/runtime/lib/math_patch.dart
File runtime/lib/math_patch.dart (right):

https://codereview.chromium.org/22943005/diff/9001/runtime/lib/math_patch.dar...
runtime/lib/math_patch.dart:23: if (exponent is! num) {
On 2013/08/20 10:56:23, floitsch wrote:
> remove the check.

Done.

https://codereview.chromium.org/22943005/diff/9001/sdk/lib/math/math.dart
File sdk/lib/math/math.dart (right):

https://codereview.chromium.org/22943005/diff/9001/sdk/lib/math/math.dart#new...
sdk/lib/math/math.dart:153: * - if `x` is Infinity and `y` is negative, the
result is 0.0.
On 2013/08/20 10:56:23, floitsch wrote:
> strictly negative
> although it is not necessary since the y==0 already handled that case.

Done.

https://codereview.chromium.org/22943005/diff/9001/sdk/lib/math/math.dart#new...
sdk/lib/math/math.dart:154: * - if `x` is Infinity and `y` is positive, the
result is Infinity.
On 2013/08/20 10:56:23, floitsch wrote:
> strictly positive

Done.

https://codereview.chromium.org/22943005/diff/9001/tests/lib/math/double_pow_...
File tests/lib/math/double_pow_test.dart (right):

https://codereview.chromium.org/22943005/diff/9001/tests/lib/math/double_pow_...
tests/lib/math/double_pow_test.dart:56: main() {
On 2013/08/20 10:56:23, floitsch wrote:
> add documentation edge-cases one by one (as written in the documentation).

Done.

[Lasse Reichstein Nielsen, 2013-08-20 12:23:15]

Committed patchset #4 manually as r26347 (presubmit successful).