On Sun, Jan 24, 2016 at 07:11:08PM +0100, Simon Jakobi wrote:
I want to test whether a sequence of the characters 'A' and 'B' can represent a sequence of the symbols x and y where x may be represented by one or more 'A's and y may be represented by one or more 'A's or one or more 'B's.
In code, I would like to see the following:
λ> "AABB" `represents` [x, y] True λ> "AA" `represents` [x, y] True
Hello Simon, if I understood your specification correctly, there would be multiple ways to parse the string "AAA": - 3 'x' elements ("A", "A", "A") - 2 'x' elements ("AA", "A") - 2 'x' elements again (first one shorter) ("A", "AA") - 1 'x' element ("AAA") Which of these four should we choose? Maybe "parse as many As as possible without consuming the A followed by a series of B"? If so, a useful combinator is `notFollowedBy` (present in parsec, pretty sure is in attoparsec too, if not it can be easily replicated). Does that help?