[Haskell-cafe] Parsing, infixes and on-the-fly precedence

[Chris Wong]

Hi Jeffrey,

On Mon, Sep 28, 2015 at 8:28 PM, Jeffrey Brown <jeffbrown.the at gmail.com> wrote:
> I imagine a parser that operates on (String,[String]) pairs, for which the
> second element allows the user to define precedence on the fly.
>
> For instance, it would read the pair
>   (x,y) = ("a , b : c", [":" , ","])
> as
>   "(a , (b : c))"
> because y informs the parser that in x the colon binds first, then the
> comma.
>
> I know it is possible, because Haskell does it already! In Haskell we can
> define novel infix operators on the fly, including their precedence relative
> to each other.
>
> I don't know how, though, so that's my question.

You might like to look at Text.Parsec.Token[1], which does exactly
what you describe.

[1] https://hackage.haskell.org/package/parsec-3.1.9/docs/Text-Parsec-Expr.html

> --
> Jeffrey Benjamin Brown
>
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-- 
Chris Wong (https://lambda.xyz)

"I fear that Haskell is doomed to succeed."
    -- Tony Hoare