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Make sure range(start; step, length) uses TwicePrecision when possible #44313

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merged 5 commits into from
Feb 23, 2022
Merged

Make sure range(start; step, length) uses TwicePrecision when possible #44313

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d711637
twiceprecision: use IEEEFloat instead of Union
jipolanco Feb 23, 2022
1c5dd91
Add range_start_step_length definition
jipolanco Feb 23, 2022
0e1f7a8
Add test
jipolanco Feb 23, 2022
8cf3581
Fix `range(; step, stop, length)`
jipolanco Feb 23, 2022
dd6c2c6
Add more tests
jipolanco Feb 23, 2022
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12 changes: 10 additions & 2 deletions base/twiceprecision.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -408,7 +408,7 @@ function floatrange(a::AbstractFloat, st::AbstractFloat, len::Real, divisor::Abs
steprangelen_hp(T, (a,divisor), (st,divisor), nbitslen(T, len, 1), len, oneunit(len))
end

function (:)(start::T, step::T, stop::T) where T<:Union{Float16,Float32,Float64}
function (:)(start::T, step::T, stop::T) where T<:IEEEFloat
step == 0 && throw(ArgumentError("range step cannot be zero"))
# see if the inputs have exact rational approximations (and if so,
# perform all computations in terms of the rationals)
Expand Down Expand Up @@ -453,7 +453,10 @@ end
step(r::StepRangeLen{T,TwicePrecision{T},TwicePrecision{T}}) where {T<:AbstractFloat} = T(r.step)
step(r::StepRangeLen{T,TwicePrecision{T},TwicePrecision{T}}) where {T} = T(r.step)

function range_start_step_length(a::T, st::T, len::Integer) where T<:Union{Float16,Float32,Float64}
range_start_step_length(a, st::IEEEFloat, len::Integer) =
range_start_step_length(oftype(st, a), st, len)

function range_start_step_length(a::T, st::T, len::Integer) where T<:IEEEFloat
len = len + 0 # promote with Int
start_n, start_d = rat(a)
step_n, step_d = rat(st)
Expand All @@ -471,6 +474,11 @@ function range_start_step_length(a::T, st::T, len::Integer) where T<:Union{Float
steprangelen_hp(T, a, st, 0, len, 1)
end

function range_step_stop_length(step::IEEEFloat, stop, len::Integer)
r = range_start_step_length(stop, negate(step), len)
reverse(r)
end

# This assumes that r.step has already been split so that (0:len-1)*r.step.hi is exact
function unsafe_getindex(r::StepRangeLen{T,<:TwicePrecision,<:TwicePrecision}, i::Integer) where T
# Very similar to _getindex_hiprec, but optimized to avoid a 2nd call to add12
Expand Down
12 changes: 12 additions & 0 deletions test/ranges.jl
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Expand Up @@ -1612,6 +1612,18 @@ end
@test x isa StepRangeLen{Float64,Base.TwicePrecision{Float64},Base.TwicePrecision{Float64}}
end

@testset "Issue #44292" begin
let x = @inferred range(0, step=0.2, length=5)
@test x isa StepRangeLen{Float64,Base.TwicePrecision{Float64},Base.TwicePrecision{Float64}}
@test x == [0.0, 0.2, 0.4, 0.6, 0.8]
end

let x = @inferred range(stop=1, step=0.2, length=5)
@test x isa StepRangeLen{Float64,Base.TwicePrecision{Float64},Base.TwicePrecision{Float64}}
@test x == [0.2, 0.4, 0.6, 0.8, 1.0]
end
end

@testset "Views of ranges" begin
@test view(Base.OneTo(10), Base.OneTo(5)) === Base.OneTo(5)
@test view(1:10, 1:5) === 1:5
Expand Down