https://issues.dlang.org/show_bug.cgi?id=20069
Issue ID: 20069
Summary: std.format digit grouping separator (aka thousands
separator) needs to be revisited
Product: D
Version: D2
Hardware: x86_64
OS: Linux
Status: NEW
Severity: enhancement
Priority: P1
Component: phobos
Assignee: [email protected]
Reporter: [email protected]
Currently the default separator used by std.format is always ','.
With the C locale (default) the number 123456.789 is thus formatted as
"123,456.789,000".
If another locale is activated, the output does not match the locale and
sometimes even becomes a mess:
writefln("%,f", 123456.789)
de_DE.UTF-8: "1,234,56,,789,000"
fr_FR.UTF-8: "1,234,56,,789,000"
fr_CH.UTF-8: "123,456.789,000"
en_IN.UTF-8: "123,456.789,000"
nl_NL.UTF-8: "1,234,56,,789,000"
hak_TW: "123,456.789,000"
ps_AF: "12,345,6٫,789,000"
unm_US: "123,456.789,000"
The printf as defined by POSIX formats the same case as follows (I'd regard
this as the generally correct formatting):
printf("%'f", 123456.789)
C: "123456.789000"
de_DE.UTF-8: "123.456,789000"
fr_FR.UTF-8: "123 456,789000"
fr_CH.UTF-8: "123'456.789000"
en_IN.UTF-8: "1,23,456.789000" (non-uniform group size!)
nl_NL.UTF-8: "123456,789000"
hak_TW: "12,3456.789000"
ps_AF: "123٬456٫789000"
unm_US: "12 34 56.789000"
Grouping after the decimal separator should probably be made optional as it
kind of is nonstandard behavior (scanf doesn't appear to handle such grouping,
for example) yet useful for human interfacing nonetheless.
Grouping should, unless overridden, behave according to the active locale, for
the C locale, which is active by default, this means no grouping at all. This
is useful because a formatted number such as 100000 is otherwise ambiguous for
comma-decimal-users by default ("100,000").
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