Merge pull request #94 from JuliaMath/os/fix-BigFloat-pow

fix BigFloat pow

Author: oscardssmith

src/NaNMath.jl

@@ -68,6 +68,12 @@ Base.@assume_effects :total pow(x::Float32, y::Float32) = ccall((:powf,libm), Fl
 # e.g. `pow(::Float32, ::Int)` ends up calling `pow(::Float32, ::Float32)`
 pow(x::Real, y::Real) = pow(promote(x, y)...)
 pow(x::T, y::T) where {T<:Real} = pow(float(x), float(y))
+function pow(x::T, y::T) where {T<:AbstractFloat}
+    if x < 0 && !isinteger(y)
+        return T(NaN)
+    end
+    return x ^ y
+end
 pow(x, y) = ^(x, y)
 
 # The following combinations are safe, so we can fall back to ^

test/runtests.jl

@@ -3,8 +3,10 @@ using Test
 
 @test isnan(NaNMath.log(-10))
 @test isnan(NaNMath.log1p(-100))
-@test isnan(NaNMath.pow(-1.5,2.3))
-@test isnan(NaNMath.pow(-1.5f0,2.3f0))
+for T in (Float16, Float32, Float64, BigFloat)
+    @test isnan(NaNMath.pow(T(-1.5),T(2.3)))
+    @test NaNMath.pow(T(-1.5),T(5)) ≈ T(-1.5) ^ T(5)
+end
 @test isnan(NaNMath.pow(-1.5,2.3f0))
 @test isnan(NaNMath.pow(-1.5f0,2.3))
 @test NaNMath.pow(-1.5f0,2) isa Float32