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Comparison with Rational #114

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May 5, 2020
Merged

Comparison with Rational #114

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75 changes: 75 additions & 0 deletions src/DecFP.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -516,6 +516,81 @@ Base.:^(x::DecimalFloatingPoint, p::Integer) = x^oftype(x, p)
@inline Base.literal_pow(::typeof(^), x::DecimalFloatingPoint, ::Val{2}) = x*x
@inline Base.literal_pow(::typeof(^), x::DecimalFloatingPoint, ::Val{3}) = x*x*x

# decompose is needed for hash() and comparison with Rational
function Base.decompose(x::DecimalFloatingPoint)::Tuple{BigInt, Int, BigInt}
isnan(x) && return 0, 0, 0
isinf(x) && return ifelse(signbit(x), -1, 1), 0, 0
iszero(x) && return 0, 0, ifelse(signbit(x), -1, 1)
s, e = sigexp(x)
if e >= 0
if e <= 27
return s * BigInt(Int64(5)^e), e, ifelse(signbit(x), -1, 1)
else
return s * BigInt(5)^e, e, ifelse(signbit(x), -1, 1)
end
else
e2 = -e
q, r = divrem(s, oftype(s, 5))
while e2 > 0 && r == 0
s = q
q, r = divrem(s, oftype(s, 5))
e2 -= 1
end
if e2 <= 27
return copysign(s, x), e, Int64(5)^e2
else
return copysign(s, x), e, BigInt(5)^e2
end
end
end

function sigexp(x::Dec32)
n = reinterpret(UInt32, x)
if n & 0x60000000 == 0x60000000
s = ((n & 0x001fffff) | 0x00800000) % Int32
e = ((n & 0x1fe00000) >> 21) % Int
else
s = (n & 0x007fffff) % Int32
e = ((n & 0x7f800000) >> 23) % Int
end
e -= 101
return s, e
end

function sigexp(x::Dec64)
n = reinterpret(UInt64, x)
if n & 0x6000000000000000 == 0x6000000000000000
s = ((n & 0x0007ffffffffffff) | 0x0020000000000000) % Int64
e = ((n & 0x1ff8000000000000) >> 51) % Int
else
s = (n & 0x001fffffffffffff) % Int64
e = ((n & 0x7fe0000000000000) >> 53) % Int
end
e -= 398
return s, e
end

function sigexp(x::Dec128)
n = reinterpret(UInt128, x)
if n & 0x60000000000000000000000000000000 == 0x60000000000000000000000000000000
s = ((n & 0x00007fffffffffffffffffffffffffff) | 0x00020000000000000000000000000000) % Int128
e = ((n & 0x1fff8000000000000000000000000000) >> 111) % Int
else
s = (n & 0x0001ffffffffffffffffffffffffffff) % Int128
e = ((n & 0x7ffe0000000000000000000000000000) >> 113) % Int
end
e -= 6176
return s, e
end

function Base.:(==)(x::DecimalFloatingPoint, q::Rational)
if isfinite(x)
((q.den == 1) | (q.den % 2 == 0) | (q.den % 5 == 0)) & (x*q.den == q.num)
else
x == q.num/q.den
end
end

# used for next/prevfloat:
const pinf128 = _parse(Dec128, "+Inf")
const minf128 = _parse(Dec128, "-Inf")
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15 changes: 15 additions & 0 deletions test/runtests.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -191,6 +191,21 @@ for T in (Dec32, Dec64, Dec128)
@test T(2)^2 === T(4)
@test T(2)^3 === T(8)

@test T("0.1") == 1//10
@test 1//10 == T("0.1")
@test T("-0.1") == -1//10
@test T("0.2") == 1//5
@test T("0.5") == 1//2
@test T(1) == 1//1
@test T(0) == 0//1
@test T(Inf) == 1//0
@test T(-Inf) == -1//0
@test T(1) / T(3) != 1//3
@test T(1) / T(3) < 1//3
@test T(1) / T(3) <= 1//3
@test T(2) / T(3) > 2//3
@test T(2) / T(3) >= 2//3

for x = -5.0:0.25:5.0, y = -5.0:0.25:5.0
@test isequal(rem(T(x), T(y)), rem(x, y))
@test isequal(rem(T(x), T(y), RoundNearest), rem(x, y, RoundNearest))
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