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Fix rounding when converting Rational to BigFloat #59063

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Merged
merged 7 commits into from
Jul 27, 2025
Merged

Fix rounding when converting Rational to BigFloat #59063

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81676ec
Fix rounding when converting Rational to BigFloat
OlivierHnt Jul 22, 2025
0d914c4
Update mpfr.jl
OlivierHnt Jul 22, 2025
299fc8e
Minor cleanup
OlivierHnt Jul 22, 2025
3be9e73
Minor cleanup
OlivierHnt Jul 22, 2025
e6e98df
Add tests
OlivierHnt Jul 24, 2025
d98ad98
Fix typo
OlivierHnt Jul 25, 2025
d2148ea
Merge branch 'master' into patch-1
IanButterworth Jul 27, 2025
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12 changes: 9 additions & 3 deletions base/mpfr.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -391,13 +391,19 @@ BigFloat(x::Union{UInt8,UInt16,UInt32}, r::MPFRRoundingMode=rounding_raw(BigFloa
BigFloat(x::Union{Float16,Float32}, r::MPFRRoundingMode=rounding_raw(BigFloat); precision::Integer=_precision_with_base_2(BigFloat)) =
BigFloat(Float64(x), r; precision=precision)

function BigFloat(x::Rational, r::MPFRRoundingMode=rounding_raw(BigFloat); precision::Integer=_precision_with_base_2(BigFloat))
function BigFloat(x::Rational, r::Base.MPFR.MPFRRoundingMode=Base.MPFR.MPFRRoundNearest; precision::Integer=_precision_with_base_2(BigFloat))
r_den = _opposite_round(r)
setprecision(BigFloat, precision) do
setrounding_raw(BigFloat, r) do
BigFloat(numerator(x))::BigFloat / BigFloat(denominator(x))::BigFloat
Base.MPFR.setrounding_raw(BigFloat, r) do
BigFloat(numerator(x))::BigFloat / BigFloat(denominator(x), r_den)::BigFloat
end
end
end
function _opposite_round(r::Base.MPFR.MPFRRoundingMode)
r == MPFR.MPFRRoundUp && return MPFR.MPFRRoundDown
r == MPFR.MPFRRoundDown && return MPFR.MPFRRoundUp
return r
end

function tryparse(::Type{BigFloat}, s::AbstractString; base::Integer=0, precision::Integer=_precision_with_base_2(BigFloat), rounding::MPFRRoundingMode=rounding_raw(BigFloat))
!isempty(s) && isspace(s[end]) && return tryparse(BigFloat, rstrip(s), base = base)
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