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Merged
merged 1 commit into from
Aug 24, 2020
Merged

Add checked_abs, wrapping_abs and saturating_abs #217

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26 changes: 21 additions & 5 deletions src/FixedPointNumbers.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,8 @@ import Base: ==, <, <=, -, +, *, /, ~, isapprox,
import Statistics # for _mean_promote
import Random: Random, AbstractRNG, SamplerType, rand!

import Base.Checked: checked_neg, checked_add, checked_sub, checked_mul, checked_div
import Base.Checked: checked_neg, checked_abs, checked_add, checked_sub, checked_mul,
checked_div

using Base: @pure

Expand All @@ -36,8 +37,8 @@ export
# Q and N typealiases are exported in separate source files
# Functions
scaledual,
wrapping_neg, wrapping_add, wrapping_sub, wrapping_mul,
saturating_neg, saturating_add, saturating_sub, saturating_mul
wrapping_neg, wrapping_abs, wrapping_add, wrapping_sub, wrapping_mul,
saturating_neg, saturating_abs, saturating_add, saturating_sub, saturating_mul

include("utilities.jl")

Expand Down Expand Up @@ -202,13 +203,17 @@ float(x::FixedPoint) = convert(floattype(x), x)

# wrapping arithmetic
wrapping_neg(x::X) where {X <: FixedPoint} = X(-x.i, 0)
wrapping_abs(x::X) where {X <: FixedPoint} = X(abs(x.i), 0)
wrapping_add(x::X, y::X) where {X <: FixedPoint} = X(x.i + y.i, 0)
wrapping_sub(x::X, y::X) where {X <: FixedPoint} = X(x.i - y.i, 0)

# saturating arithmetic
saturating_neg(x::X) where {X <: FixedPoint} = X(~min(x.i - true, x.i), 0)
saturating_neg(x::X) where {X <: FixedPoint{<:Unsigned}} = zero(X)

saturating_abs(x::X) where {X <: FixedPoint} =
X(ifelse(signbit(abs(x.i)), typemax(x.i), abs(x.i)), 0)

saturating_add(x::X, y::X) where {X <: FixedPoint} =
X(x.i + ifelse(x.i < 0, max(y.i, typemin(x.i) - x.i), min(y.i, typemax(x.i) - x.i)), 0)
saturating_add(x::X, y::X) where {X <: FixedPoint{<:Unsigned}} = X(x.i + min(~x.i, y.i), 0)
Expand All @@ -217,8 +222,13 @@ saturating_sub(x::X, y::X) where {X <: FixedPoint} =
X(x.i - ifelse(x.i < 0, min(y.i, x.i - typemin(x.i)), max(y.i, x.i - typemax(x.i))), 0)
saturating_sub(x::X, y::X) where {X <: FixedPoint{<:Unsigned}} = X(x.i - min(x.i, y.i), 0)


# checked arithmetic
checked_neg(x::X) where {X <: FixedPoint} = checked_sub(zero(X), x)
function checked_abs(x::X) where {X <: FixedPoint}
abs(x.i) >= 0 || throw_overflowerror_abs(x)
X(abs(x.i), 0)
end
function checked_add(x::X, y::X) where {X <: FixedPoint}
r, f = Base.Checked.add_with_overflow(x.i, y.i)
z = X(r, 0) # store first
Expand All @@ -235,7 +245,7 @@ end
# default arithmetic
const DEFAULT_ARITHMETIC = :wrapping

for (op, name) in ((:-, :neg), )
for (op, name) in ((:-, :neg), (:abs, :abs))
f = Symbol(DEFAULT_ARITHMETIC, :_, name)
@eval begin
$op(x::X) where {X <: FixedPoint} = $f(x)
Expand Down Expand Up @@ -298,7 +308,7 @@ for f in (:(==), :<, :<=, :div, :fld, :fld1)
$f(x::X, y::X) where {X <: FixedPoint} = $f(x.i, y.i)
end
end
for f in (:~, :abs)
for f in (:~, )
@eval begin
$f(x::X) where {X <: FixedPoint} = X($f(x.i), 0)
end
Expand Down Expand Up @@ -458,6 +468,12 @@ end
showtype(io, typeof(x))
throw(OverflowError(String(take!(io))))
end
@noinline function throw_overflowerror_abs(@nospecialize(x))
io = IOBuffer()
print(io, "abs(", x, ") overflowed for type ")
showtype(io, typeof(x))
throw(OverflowError(String(take!(io))))
end

function Random.rand(r::AbstractRNG, ::SamplerType{X}) where X <: FixedPoint
X(rand(r, rawtype(X)), 0)
Expand Down
20 changes: 20 additions & 0 deletions test/fixed.jl
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Expand Up @@ -302,6 +302,26 @@ end
end
end

@testset "abs" begin
for F in target(Fixed; ex = :thin)
@test wrapping_abs(typemax(F)) === typemax(F)
@test saturating_abs(typemax(F)) === typemax(F)
@test checked_abs(typemax(F)) === typemax(F)

@test wrapping_abs(typemin(F)) === typemin(F)
@test saturating_abs(typemin(F)) === typemax(F)
@test_throws OverflowError checked_abs(typemin(F))
end
for F in target(Fixed, :i8; ex = :thin)
xs = typemin(F):eps(F):typemax(F)
fabs(x) = abs(float(x))
@test all(x -> wrapping_abs(x) === (x > 0 ? x : wrapping_neg(x)), xs)
@test all(x -> saturating_abs(x) === clamp(fabs(x), F), xs)
@test all(x -> !(typemin(F) <= fabs(x) <= typemax(F)) ||
wrapping_abs(x) === checked_abs(x) === fabs(x) % F, xs)
end
end

@testset "add" begin
for F in target(Fixed; ex = :thin)
@test wrapping_add(typemin(F), typemin(F)) === zero(F)
Expand Down
20 changes: 20 additions & 0 deletions test/normed.jl
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Expand Up @@ -323,6 +323,26 @@ end
end
end

@testset "abs" begin
for N in target(Normed; ex = :thin)
@test wrapping_abs(typemax(N)) === typemax(N)
@test saturating_abs(typemax(N)) === typemax(N)
@test checked_abs(typemax(N)) === typemax(N)

@test wrapping_abs(typemin(N)) === typemin(N)
@test saturating_abs(typemin(N)) === typemin(N)
@test checked_abs(typemin(N)) === typemin(N)
end
for N in target(Normed, :i8; ex = :thin)
xs = typemin(N):eps(N):typemax(N)
fabs(x) = abs(float(x))
@test all(x -> wrapping_abs(x) === (x > 0 ? x : wrapping_neg(x)), xs)
@test all(x -> saturating_abs(x) === clamp(fabs(x), N), xs)
@test all(x -> !(typemin(N) <= fabs(x) <= typemax(N)) ||
wrapping_abs(x) === checked_abs(x) === fabs(x) % N, xs)
end
end

@testset "add" begin
for N in target(Normed; ex = :thin)
@test wrapping_add(typemin(N), typemin(N)) === zero(N)
Expand Down