Missing trailing context?

[neizod]

In lex/flex, there is a 'trailing context' pattern: match/require, such as

a/n

which will match only a if it follow by n. So a in and, can, another are matched, but a in alone, mask is not matched.

I found this feature is missing in PLY. Since I'm greatly rely on this feature, please add it.

[neizod]

Just report my work around. I've add a backward function for the lexer. In a lexer rule I search for the whole text. Do rexgex match unwanted part, count its length, call this function, and sub this unwanted part from the whole matched. Hooray! Its work. :)

[neizod]

Oh... that's all my bad. I'm just old fashion guy from lex/flex rexgex style. There is a better way to deal with this rexgex directly in Python:

match(?=require)

btw, could you write some short documentation on this?