Add documentation to dart:math pow function.

sdk/lib/math/math.dart

Index: sdk/lib/math/math.dart
diff --git a/sdk/lib/math/math.dart b/sdk/lib/math/math.dart
index 0c1f67fa0d00a86c6a811cd4db927aa595d6697a..93ec4164426ef8c668b0cf057b9539afe07efa05 100644
--- a/sdk/lib/math/math.dart
+++ b/sdk/lib/math/math.dart
@@ -137,7 +137,35 @@ external double atan2(num a, num b);
  * Returns [x] to the power of [exponent].
  *
  * If [x] is an [int] and [exponent] is a non-negative [int], the result is
- * an [int], otherwise the result it is a [double].
+ * an [int], otherwise both arguments are converted to doubles first, and the
+ * result is a [double].
+ *
+ * For integers, the power is always equal to the mathematical result of `x` to
+ * the power `exponent`, only limited by the available memory.
+ *
+ * For doubles, `pow(x, y)` handles edge cases as follows:
+ *
+ * - if `y` is zero (0.0 or -0.0), the result is always 1.0.
+ * - if `x` is 1.0, the result is always 1.0.
+ * - otherwise, if either `x` or `y` is NaN then the result is NaN.
+ * - if `x` is negative (but not -0.0) and `y` is a finite non-integer, the
+ *   result is NaN.
+ * - if `x` is Infinity and `y` is negative, the result is 0.0.
+ * - if `x` is Infinity and `y` is positive, the result is Infinity.
+ * - if `x` is 0.0 and `y` is negative, the result is Infinity.
+ * - if `x` is 0.0 and `y` is positive, the result is 0.0.
+ * - if `x` is -Infinity or -0.0 and `y` is an odd integer, then the result is
+ *   `-pow(-x ,y)`.
+ * - if `x` is -Infinity or -0.0 and `y` is not an odd integer, then the result
+ *   is the same as `pow(-x , y)`.
+ * - if `y` is Infinity and the absolute value of `x` is less than 1, the
+ *   result is 0.0.
+ * - if `y` is Infinity and `x` is -1, the result is 1.0.
+ * - if `y` is Infinity and the absolute value of `x` is greater than 1,
+ *   the result is Infinity.
+ * - if `y` is -Infinity, the result is `1/pow(x, Infinity)`.
+ *
+ * This corresponds to the `pow` function defined in the IEEE Standard 754-2008.
  *
  * Notice that an [int] result cannot overflow, but a [double] result might
  * be [double.INFINITY].