handle negative integer powers (#23)

Author: RalphAS

src/Quadmath.jl

@@ -324,6 +324,15 @@ round(x::Float128, r::RoundingMode{:ToZero}) = round(x)
 ## two argument
 (^)(x::Float128, y::Float128) =
     Float128(@ccall(libquadmath.powq(x::Cfloat128, y::Cfloat128)::Cfloat128))
+
+# circumvent a failure in Base
+function (^)(x::Float128, p::Integer)
+    if p >= 0
+        Base.power_by_squaring(x,p)
+    else
+        Base.power_by_squaring(inv(x),-p)
+    end
+end
 copysign(x::Float128, y::Float128) =
     Float128(@ccall(libquadmath.copysignq(x::Cfloat128, y::Cfloat128)::Cfloat128))
 hypot(x::Float128, y::Float128) =

test/runtests.jl

@@ -95,6 +95,11 @@ end
     @test fma(x,x,Float128(-1.0)) ≈ Float128(1)
 end
 
+@testset "misc. math" begin
+    x = sqrt(Float128(2.0))
+    @test abs(x^(-2) - Float128(0.5)) < 1.0e-32
+end
+
 @testset "string conversion" begin
     s = string(Float128(3.0))
     p = r"3\.0+e\+0+"