Wrong InexactError in Bool expression

[eschnett]

This expression from JSON.jl (line 11) yields InexactError since today:

Bool[isprint(c) && !iscntrl(c) && !(c in ['\\','"']) for c in '\x00':'\x7F']

The problem seems to be the lower bound '\x00' of the character range.

[eschnett]

I see this line in "range.jl":

    UnitRange(start, stop) = new(start, ifelse(stop >= start, stop, start-1))

This unconditionally evaluates start-1, which yields InexactError for start = \x00.

[eschnett]

"range.jl" is in base...

[eschnett]

Yes, changing the ifelse to ?: corrects the problem.

[tkelman]

Might also be the fault of

julia/base/char.jl

Line 33 in 74b5c9a

-(x::Char , y::Integer) = char(int(x)-int(y))

, since I can do uint(0):uint(5) but not char(0):char(5)

[eschnett]

I don't think this line is at fault.

In this case, this line tries to convert a negative integer to a character, which is not defined. However, its inputs are '\x00' and 1 -- so there's nothing this functions could really do. (Presumably, it could define a wrap-around for characters, so that char(-1) is mapped to char(UIntMax), but that doesn't seem useful.)

[eschnett]

See #8524

[tkelman]

uint(0)-1 == 0xffffffffffffffff, so if char is a type of uint (though the signedness of char can be a platform-dependent thing, IIUC) then perhaps it should have the same behavior?