Date: Sun, 27 Jul 2014 13:36:05 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: Non-stub gettext API functions committed, ready for testing On Sun, Jul 27, 2014 at 07:23:09PM +0200, Szabolcs Nagy wrote: > * Rich Felker <dalias@...c.org> [2014-07-27 12:49:21 -0400]: > > On Sun, Jul 27, 2014 at 04:14:18PM +0200, Szabolcs Nagy wrote: > > > it shows that a c arithmetic expression parser is needed to handle plurals > > > (and the expression has to be evaluated every time dcngettext is invoked) > > > > Not necessarily. You could cache results. Or (this is likely the more > > reasonable implementation) just hard-code the expression strings that > > are actually used for real languages and implement them in C when a > > match is found. > > > > hardcoding the strings will fail if .mo files are updated to > use different expressions > > with caching the expr has to be evaluated for every uncached n Yes. > > > Plural-Forms: nplurals=2; plural=n == 1 ? 0 : 1; > > > > > > The nplurals value must be a decimal number which specifies how many > > > different plural forms exist for this language. The string following > > > plural is an expression which is using the C language syntax. > > > Exceptions are that no negative numbers are allowed, numbers must be > > > decimal, and the only variable allowed is n. > > > > This is a very poor description. Does it allow casts? Compound > > literals? Floating point? Function calls? ...? > > > > the parser in gnu gettext: > http://git.savannah.gnu.org/cgit/gettext.git/tree/gettext-runtime/intl/plural.y > > so they implement > conditional (?:) > logic (&&, ||, !) > relational (==, !=, <, >, <=, >=) > and arithmetic (+, -, *, /, %) > operators with unsigned long args only And parentheses? >From what I can tell, that's not so bad. Anyone feel like writing an expression evaluator for it? I think recursive descent is fine as long as the length of the string being evaluated is capped at a sane length (or just keep a depth counter and abort the evaluation if it exceeds some reasonable limit). Rich
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