[antlr-interest] How to handle single and plural (i.e. 'day' or 'days')

[Colin Yates]

Ah OK - many many thanks.

Col

On 26 October 2010 14:10, Martijn Reuvers <martijn.reuvers at gmail.com> wrote:

> Hello Colin,
>
> You are missing a space in between.
>
> This should work:
>
> grammar test;
>
> someRule        : DAY+
>        ;
>
> DAY     :
>        'day' 's'?
>        ;
>
> Note that DAY is a lexer token.
>
> Cheers!
> Martijn
>
>
>
> On Tue, Oct 26, 2010 at 1:34 PM, Colin Yates <colin.yates at gmail.com>
> wrote:
> > Hi,
> >
> > The user can type in '1 day' or '7 days'.  I have the following rule
> which
> > matches:
> >
> > durationPeriod: ('day' | 'days') { // do something};
> >
> > and this works fine.  I initially tried:
> >
> > durationPeriod: 'day'('s')? { // do something};
> >
> > but this never matched 'days'.
> >
> > Based on the '100 monkeys' reality I tried the following:
> >
> > durationPeriod: ('day''s')? { // do something};
> > and
> > durationPeriod: ('day')('s')? { // do something};
> >
> > but none of them matched 'days'.  The exact error is [line 1:2 no viable
> > alternative at input 'days'']
> >
> > What have I missed?  The (incredibly useful!) Syntax Diagram in antlworks
> > shows that the trailing 's' can be skipped, so I don't understand why it
> > doesn't work.
> >
> > Many thanks,
> >
> > Col
> >
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>