Re: [Chicken-hackers] [PATCH] Improve Chicken's handling of numerical syntax

[John Cowan]

Peter Bex scripsit:

> While hacking on it I found some code for OpenBSD and Windows to
> handle "nan" and "inf" syntaxes.  If I understand correctly these
> systems do not handle these in their libc's strtod() function.

Indeed, some older versions of glibc don't do well with them either.

> I believe this may actually cause compatibility problems between
> Chickens running on different OSes; some Chickens accept "+NaN" as
> valid input, while those running on Windows or OpenBSD (probably?)
> don't.  Depending on libc, Chicken might even serialize these values
> in an incompatible way such that others don't accept it.

That's just what happens: in this case, portability is more important
than backward compatibility, I think.

> To do this, there's an ugly bit of code in the attached patch which
> adds a check in convert_string_to_number() for the strings "+nan.0"
> "-nan.0", "+inf.0" and "-inf.0", case insensitively.  This conforms
> to R6RS, and most likely will end up as official R7RS syntax as well
> (there's still a proposal up in the air to make infinity represented
> by "1/0").

That proposal was voted down.  In addition, "-0.0" should be
special-cased.  Similarly, on all platforms number-to-string conversion
should bypass the C library and generate "+nan.0", "+inf.0", "-inf.0",
and "-0.0" for the appropriate values.

> Let's get the basic number parsing correct first!

Amen.

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