[Haskell-cafe] Re: ANN: weighted-regexp-0.1.0.0
sebf at informatik.uni-kiel.de
Thu Jul 29 06:18:23 EDT 2010
thanks for the examples. They show that by adding anchors, the meaning
of regular expressions is no longer compositional. For example (^|a)
accepts the empty word only if no characters have been read yet. So
(^|a) =~ ""
does hold but
a(^|a) =~ "a"
does not hold although
a =~ "a"
I deem compositionality an important property to compare the current
implementation with its specification. As, currently, I don't know how
to incorporate anchors without making a mess, I refrain from adding
them for the moment.
> A more complicated use, perhaps as part of a crazy parser:
That's a nice example and I don't know how to express this without
Underestimating the novelty of the future is a time-honored tradition.
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