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

[Martijn Reuvers]

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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