# Re: [stack] still catching up

## Louis Madon — 2000-09-14 07:00:04

    phimvt@... wrote:

     > 3. Thanks to Louis for a long discussion on Haskell. My own

    > knowledge of Haskell (0.01 %) is only marginally better than

    > my knowledge of Swahili (0.00 %).

    > I was familiar with the

    > "Any" type, and that one can have lists of "Any". Am I right

    > that in list literals every item then has to be preceded by

    > "Any", thus:

    >     [ Any 123, Any "abc", Any 'X' ]

     Yes.

     > That would make it impractical to use the Haskell reader for

    > reading Joy mixed lists or even programs.

     You could use a shorter name for the existential constructor, eg:

    [ A 123, A "abc", A 'x' ]

    sz used a slightly different approach in his "Joy in Haskell"

    interpreter; the variable typing was represented by a sum type and a set

    of associated functions, jl for list, jc for character, jb for boolean

    etc. So the above would look like,

    [ ji 123, js "abc", jc 'x' ]

    In general, I don't think you can avoid prefixing everything within a

    mixed list if the Haskell reader is to be used.

     > It is not quite

    > as bad in Prolog, where the only annoyance are the commas

    > separating the items.

     Ok, I imagine prolog is dynamically typed (?), so it would be easier

    there.

     > So a Haskell implementation of something

    > Joy-like will need a proper scanner and parser?

     I believe so, at least I can't think of a way around it. (Ofcourse a Joy

    scanner/parser isn't exactly hard to do ...)

    --

    Louis.