[ragel-users] How to avoid % action being called when the match continues?
adrian.thurston at esentire.com
Mon Dec 7 13:31:54 UTC 2009
When the '%' is seen it is unknown whether ragel is trying to parse more
of node name, or the start of L_BRACKET. Since it can't know, it does
both. Refactor like this:
step = node_name L_BRACKET @command .....
Now when command is called, it is no longer unclear what is being
parsed. The node_name is ended.
Iñaki Baz Castillo wrote:
> Hi, I have a simple grammar:
> pchar = ALPHA | DIGIT | ("%" HEXDIG HEXDIG);
> L_BRACKET = "%5b";
> node_name = ( pchar )+ -- L_BRACKET
> step = node_name %command L_BRACKET .....
> As you can see, when parsing "step" Ragel calls "command" action when
> L_BRACKET is detected. However, if any other hex-escaped appears into
> node_name then Ragel runs "command" action and then continues still into
> This is: when Ragel is parsing "node_name" and founds "%" (even if it's "%99"
> rather than "%5b") then it runs "command" action. I expected that Ragel
> wouldn't run the leaving action as it remains into node_name.
> Why doe Ragel run the % leaving action when finding "%"? perhaps because Ragel
> must take the decision per byte without reading more than one byte?
> If so, is there any way to avoid "command" action being called several times
> for the same node_name?
> To clarify: if "step" is:
> then Ragel calls "command" action 3 times (each times it finds "%").
> Thanks for any help.
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