code review 5484076: pkg/math: undo manual inlining of IsInf and IsNaN

src/pkg/math/atan2.go

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 package math
 
 // Atan2 returns the arc tangent of y/x, using
 // the signs of the two to determine the quadrant
 // of the return value.
 //
@@ skipping 11 matching lines @@
 //      Atan2(+Inf, -Inf) = 3Pi/4
 //      Atan2(-Inf, -Inf) = -3Pi/4
 //      Atan2(y, +Inf) = 0
 //      Atan2(y>0, -Inf) = +Pi
 //      Atan2(y<0, -Inf) = -Pi
 //      Atan2(+Inf, x) = +Pi/2
 //      Atan2(-Inf, x) = -Pi/2
 func Atan2(y, x float64) float64
 
 func atan2(y, x float64) float64 {
-        // TODO(rsc): Remove manual inlining of IsNaN, IsInf
-        // when compiler does it for us
         // special cases
         switch {
-        case y != y || x != x: // IsNaN(y) || IsNaN(x):
+        case IsNaN(y) || IsNaN(x):
                 return NaN()
         case y == 0:
                 if x >= 0 && !Signbit(x) {
                         return Copysign(0, y)
                 }
                 return Copysign(Pi, y)
         case x == 0:
                 return Copysign(Pi/2, y)
-        case x < -MaxFloat64 || x > MaxFloat64: // IsInf(x, 0):
-                if x > MaxFloat64 { // IsInf(x, 1) {
+        case IsInf(x, 0):
+                if IsInf(x, 1) {
                         switch {
-                        case y < -MaxFloat64 || y > MaxFloat64: // IsInf(y, -1) || IsInf(y, 1):
+                        case IsInf(y, 0):
                                 return Copysign(Pi/4, y)
                         default:
                                 return Copysign(0, y)
                         }
                 }
                 switch {
-                case y < -MaxFloat64 || y > MaxFloat64: // IsInf(y, -1) || IsInf(y, 1):
+                case IsInf(y, 0):
                         return Copysign(3*Pi/4, y)
                 default:
                         return Copysign(Pi, y)
                 }
-        case y < -MaxFloat64 || y > MaxFloat64: //IsInf(y, 0):
+        case IsInf(y, 0):
                 return Copysign(Pi/2, y)
         }
 
         // Call atan and determine the quadrant.
         q := Atan(y / x)
         if x < 0 {
                 if q <= 0 {
                         return q + Pi
                 }
                 return q - Pi
         }
         return q
 }