math: special cases for Ceil, Exp, Floor, Log, Log10

Added special case tests to all_test.go. Added tests to Floor,
in-lined tests in Exp and Log.

R=rsc
CC=golang-dev
http://codereview.appspot.com/184081

Committer: Russ Cox <rsc@golang.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/pkg/math/floor.go b/src/pkg/math/floor.go
index 2acf1e042..c5e496d8f 100644
--- a/src/pkg/math/floor.go
+++ b/src/pkg/math/floor.go
@@ -6,7 +6,15 @@ package math
 
 
 // Floor returns the greatest integer value less than or equal to x.
+//
+// Special cases are:
+//	Floor(+Inf) = +Inf
+//	Floor(-Inf) = -Inf
+//	Floor(NaN) = NaN
 func Floor(x float64) float64 {
+	if x != x || x > MaxFloat64 || x < -MaxFloat64 { // IsNaN(x) || IsInf(x, 0)
+		return x
+	}
 	if x < 0 {
 		d, fract := Modf(-x)
 		if fract != 0.0 {
@@ -19,4 +27,9 @@ func Floor(x float64) float64 {
 }
 
 // Ceil returns the least integer value greater than or equal to x.
+//
+// Special cases are:
+//	Ceil(+Inf) = +Inf
+//	Ceil(-Inf) = -Inf
+//	Ceil(NaN) = NaN
 func Ceil(x float64) float64 { return -Floor(-x) }