>Recently the use of derivations to implement regular expressions has become popular again And they're not limited to regular languages; with the right computa

>Recently the use of derivations to implement regular expressions has become popular again And they're not limited to regular languages; with the right computational tricks (lazy evaluation, coinduction, whatever you want to call it), it can be used with context-free languages in general: http://matt.might.net/papers/might2011derivatives.pdf http://matt.might.net/papers/might2011derivatives.pdf