Why does Parsec not use Control.Applicative operators

Question

Using Control.Applicative is very useful with Parsec, but you need to always hide <|> and similar objects as they conflict with Parsec's own:

import Control.Applicative hiding ((<|>), many, optional)
import Text.Parsec.Combinator
import Text.Parsec

Alternatively, as Antal S-Z points out, you can hide the Parsec version. However, as far as I can tell, this seems like an unnecessary restriction.

Why did parsec not simply implement these operators from Applicative?

Note that you can hide the operators from Parsec instead, and thus use only the nice general ones in your code. — Antal Spector-Zabusky, Apr 02 '13 at 16:17

score 20 · Accepted Answer · answered Apr 02 '13 at 15:53

20

It's for historic reasons. The Parsec library predates the discovery of applicative functors and so it wasn't designed with them in mind. And I guess no one has taken the time to update Parsec to use Control.Applicative. There is no deep fundamental reason for not doing it.

answered Apr 02 '13 at 15:53

svenningsson

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I think there's also a problem with fixities, Parsec's `<|>` has `infixr 1` for example, while Alternative's has `infixl 4`. – David Apr 11 '13 at 08:08

Why does Parsec not use Control.Applicative operators

1 Answers1