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| author | Paul Eggert <eggert@cs.ucla.edu> | 2018-07-26 00:34:10 -0700 |
|---|---|---|
| committer | Paul Eggert <eggert@cs.ucla.edu> | 2018-07-26 00:39:17 -0700 |
| commit | 4a56ca5bbfabbb9c581828cd91648346e6b03844 (patch) | |
| tree | 90b804ea4ec22a8b7be181f0b505b57c40a85c27 /etc | |
| parent | 19f5f7b19b0dcdae87476a3fd51c41f840b2b80f (diff) | |
| download | emacs-4a56ca5bbfabbb9c581828cd91648346e6b03844.tar.gz | |
%o and %x can now format signed integers
Optionally treat integers as signed numbers with %o
and %x format specifiers, instead of treating them as
a machine-dependent two’s complement representation.
This option is more machine-independent, allows formats
like "#x%x" to be useful for reading later, and is
better-insulated for future changes involving bignums.
Setting the new variable ‘binary-as-unsigned’ to nil
enables the new behavior (Bug#32252).
This is a simplified version of the change proposed in:
https://lists.gnu.org/r/emacs-devel/2018-07/msg00763.html
I simplified that proposal by omitting bitwidth modifiers, as
I could not find an any example uses in the Emacs source code
that needed them and doing them correctly would have been
quite a bit more work for apparently little benefit.
* doc/lispref/strings.texi (Formatting Strings):
Document that %x and %o format negative integers in a
platform-dependent way. Also, document how to format
numbers so that the same values can be read back in.
* etc/NEWS: Document the change.
* src/editfns.c (styled_format): Treat integers as signed
numbers even with %o and %x, if binary-as-unsigned is nil.
Support the + and space flags with %o and %x, since they’re
about signs.
(syms_of_editfns): New variable binary-as-unsigned.
* test/src/editfns-tests.el (read-large-integer):
Test that maximal integers can be read after printing
with all integer formats, if binary-as-unsigned is nil.
Diffstat (limited to 'etc')
| -rw-r--r-- | etc/NEWS | 9 |
1 files changed, 9 insertions, 0 deletions
@@ -812,6 +812,15 @@ between two strings. ** 'print-quoted' now defaults to t, so if you want to see (quote x) instead of 'x you will have to bind it to nil where applicable. ++++ +** Numbers formatted via %o or %x may now be formatted as signed integers. +This avoids problems in calls like (read (format "#x%x" -1)), and is +more compatible with bignums, a planned feature. To get this +behavior, set the experimental variable binary-as-unsigned to nil, +and if the new behavior breaks your code please email +32252@debbugs.gnu.org. Because %o and %x can now format signed +integers, they now support the + and space flags. + ** To avoid confusion caused by "smart quotes", the reader signals an error when reading Lisp symbols which begin with one of the following quotation characters: ‘’‛“”‟〞＂＇. A symbol beginning with such a |