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fix negative integer powers #95

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merged 1 commit into from
May 9, 2019
Merged

fix negative integer powers #95

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7 changes: 7 additions & 0 deletions src/DecFP.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -494,6 +494,13 @@ function Base.sqrt(z::Complex{T}) where {T<:DecimalFloatingPoint}
Complex(ξ,η)
end

# see issue #92 — the fallback power_by_squaring fails for p < 0, and this is more accurate:
Base.:^(x::DecimalFloatingPoint, p::Integer) = x^oftype(x, p)
@inline Base.literal_pow(::typeof(^), x::DecimalFloatingPoint, ::Val{0}) = one(x)
@inline Base.literal_pow(::typeof(^), x::DecimalFloatingPoint, ::Val{1}) = x
@inline Base.literal_pow(::typeof(^), x::DecimalFloatingPoint, ::Val{2}) = x*x
@inline Base.literal_pow(::typeof(^), x::DecimalFloatingPoint, ::Val{3}) = x*x*x

# used for next/prevfloat:
const pinf128 = _parse(Dec128, "+Inf")
const minf128 = _parse(Dec128, "-Inf")
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10 changes: 10 additions & 0 deletions test/runtests.jl
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Expand Up @@ -147,6 +147,16 @@ for T in (Dec32, Dec64, Dec128)
@test xd == Tf(x) == T(Tf(x)) == Tf(xd)
end

# issue #92
p = -2
@test T(2)^-2 == parse(T, "0.25") == T(2)^p

# exercise literal_pow
@test T(2)^0 === T(1)
@test T(2)^1 === T(2)
@test T(2)^2 === T(4)
@test T(2)^3 === T(8)

@test trunc(T(2.7)) === floor(T(2.7)) === round(T(2.7), RoundDown) === round(T(2.7), RoundToZero) === T(2)
@test ceil(T(2.3)) === round(T(2.3), RoundUp) === round(T(2.3), RoundFromZero) === T(3)
@test round(T(1.5)) === round(T(2.5)) === round(T(1.5), RoundNearest) === round(T(2.5), RoundNearest) === T(2)
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