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Re: integer overflow handling for most-negative-fixnum
From: |
Stefan Monnier |
Subject: |
Re: integer overflow handling for most-negative-fixnum |
Date: |
Sat, 21 Jul 2018 16:42:03 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) |
>> When the user wrote #x3fffffffffffffff to mean "the positive number
>> written as 3fffffffffffffff in hexadecimal"
> There's no such positive number, at least not as fixnum.
That's no excuse to turn around and return a negative number instead.
If I try to read too large a decimal number, Emacs signals an
`overflow-error` instead of returning a negative number, so it makes
sense to do the same for hexadecimal numbers.
>> You can only read it as "-1" based on an assumption of fixed-width
>> two's-complement representation but the bitwidth of Emacs numbers is
>> something that can change between Emacs versions and
>> compilation options.
> I'm talking about an Emacs with 64-bit EMACS_INT.
Right, but the reader is designed to `read` files which are usually not
specific to a given build (historically, there have been some
build-dependence on the result of `read`, but we've generally
considered them as bugs or misfeatures).
Stefan
- Re: integer overflow handling for most-negative-fixnum, (continued)
- Re: integer overflow handling for most-negative-fixnum, Helmut Eller, 2018/07/21
- Re: integer overflow handling for most-negative-fixnum, Helmut Eller, 2018/07/21
- Re: integer overflow handling for most-negative-fixnum, Paul Eggert, 2018/07/23
- Re: integer overflow handling for most-negative-fixnum, Eli Zaretskii, 2018/07/21
- Re: integer overflow handling for most-negative-fixnum, Paul Eggert, 2018/07/21
- Re: integer overflow handling for most-negative-fixnum, Eli Zaretskii, 2018/07/21
- Re: integer overflow handling for most-negative-fixnum, Stefan Monnier, 2018/07/21
- Re: integer overflow handling for most-negative-fixnum, Eli Zaretskii, 2018/07/21
- Re: integer overflow handling for most-negative-fixnum,
Stefan Monnier <=
- Re: integer overflow handling for most-negative-fixnum, Helmut Eller, 2018/07/21
- Re: integer overflow handling for most-negative-fixnum, Paul Eggert, 2018/07/21
- Re: integer overflow handling for most-negative-fixnum, Andy Moreton, 2018/07/23
- Re: integer overflow handling for most-negative-fixnum, Paul Eggert, 2018/07/23
- Re: integer overflow handling for most-negative-fixnum, Andy Moreton, 2018/07/23
- Re: integer overflow handling for most-negative-fixnum, Andreas Schwab, 2018/07/24
- Re: integer overflow handling for most-negative-fixnum, Andy Moreton, 2018/07/24
Re: integer overflow handling for most-negative-fixnum, Paul Eggert, 2018/07/21