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Improve char to int parsing, and add tryparse method #59603

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Improve char to int parsing, and add tryparse method #59603

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bb0b8b8
Optimise parse(<:Integer, ::AbstractChar)
jakobnissen Sep 19, 2025
4618853
Add tryparse(::T<:Integer, ::AbstractChar)
jakobnissen Sep 21, 2025
4a9de72
Format to align with rest of file
jakobnissen Sep 22, 2025
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33 changes: 25 additions & 8 deletions base/parse.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -38,14 +38,31 @@ julia> parse(Complex{Float64}, "3.2e-1 + 4.5im")
parse(T::Type, str; base = Int)
parse(::Type{Union{}}, slurp...; kwargs...) = error("cannot parse a value as Union{}")

function parse(::Type{T}, c::AbstractChar; base::Integer = 10) where T<:Integer
a::Int = (base <= 36 ? 10 : 36)
2 <= base <= 62 || throw(ArgumentError("invalid base: base must be 2 ≤ base ≤ 62, got $base"))
d = '0' <= c <= '9' ? c-'0' :
'A' <= c <= 'Z' ? c-'A'+10 :
'a' <= c <= 'z' ? c-'a'+a : throw(ArgumentError("invalid digit: $(repr(c))"))
d < base || throw(ArgumentError("invalid base $base digit $(repr(c))"))
convert(T, d)
@noinline function _invalid_base(base)
throw(ArgumentError("invalid base: base must be 2 ≤ base ≤ 62, got $base"))
end

@noinline _invalid_digit(base, char) = throw(ArgumentError("invalid base $base digit $(repr(char))"))
Comment on lines +41 to +45
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These are weirdly inconsistent?

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One is longer than the other, and therefore the line needs to be broken up.


function parse_char(::Type{T}, c::AbstractChar, base::Integer, throw::Bool) where {T <: Integer}
a::UInt8 = (base <= 36 ? 10 : 36)
(2 <= base <= 62) || (throw ? _invalid_base(base) : return nothing)
base = base % UInt8
codepoint = c > 'z' ? 0xff : UInt8(c)
d = UInt8('0') ≤ codepoint ≤ UInt8('9') ? codepoint - UInt8('0') :
UInt8('A') ≤ codepoint ≤ UInt8('Z') ? codepoint - UInt8('A') + UInt8(10) :
UInt8('a') ≤ codepoint ≤ UInt8('z') ? codepoint - UInt8('a') + a :
0xff
d < base || (throw ? _invalid_digit(base, c) : return nothing)
convert(T, d)::T
end

function parse(::Type{T}, c::AbstractChar; base::Integer=10) where {T <: Integer}
@inline parse_char(T, c, base, true)
end

function tryparse(::Type{T}, c::AbstractChar; base::Integer=10) where {T <: Integer}
@inline parse_char(T, c, base, false)
end

function parseint_iterate(s::AbstractString, startpos::Int, endpos::Int)
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7 changes: 7 additions & 0 deletions test/parse.jl
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Expand Up @@ -29,6 +29,13 @@
@test parse(Int, 'a', base=16) == 10
@test_throws ArgumentError parse(Int, 'a')
@test_throws ArgumentError parse(Int,typemax(Char))

@test tryparse(Int, '8') === 8
@test tryparse(Int, 'a') === nothing
@test tryparse(Int, 'a'; base=11) === 10
@test tryparse(Int32, 'a'; base=11) === Int32(10)
@test tryparse(UInt8, 'f'; base=16) === 0x0f
@test tryparse(UInt8, 'f'; base=15) === nothing
end

# Issue 29451
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