[Haskell-cafe] Ternary infix expression parser

[Jon Fairbairn]

Jeffrey Brown <jeffbrown.the at gmail.com> writes:

> I want to write a parser that lets someone write "(a #uses b) #because (c
> #needs d)" and read it into a tree:
>
>   data Tree = Tree String Tree Tree | Leaf String
>   magic "(a #uses b) #because (c #needs d)"
>     = Tree "because" (Tree "uses" (Leaf "a") (Leaf "b"))
>                      (Tree "needs" (Leaf "c") (Leaf "d"))
>
> I thought I could use Text.Megaparsec.Expr for it, but now I realize it
> hadnles binary operations, and this is a ternary one.
>
> Suggestions?

Parse it as three binary ones and check the tree afterwards?

-- 
Jón Fairbairn                                 Jon.Fairbairn at cl.cam.ac.uk