On Tue, Apr 17, 2012 at 05:55:36PM +0200, Waldek Hebisch wrote:
[..]
> >
> > ------------------------------------------------------------------------
> > )abbrev category UNPARSE UnparserCategory
> > UnparserCategory(T : Type) : Category == with (show : T -> String)
> >
> > )abbrev package LUNPARS ListUnparser
> > ListUnparser(T : Type, UT : UnparserCategory(T)) : _
> > UnparserCategory(List(T))
> > == add
> > show(xs : List T) : String ==
> > empty? xs => "[]"
> > x := first xs
> > xs := rest xs
> > str := concat("[", show(x) $UT)
> > while not empty?(xs) repeat
> > x := first xs
> > xs := rest xs
> > str := concat[str, ",", show(x) $UT]
> > concat(str, "]")
>
> ^^^^ Indentation error
> str
> > ------------------------------------------------------------------------
> >
[..]
> (3) -> l := [[-1, 2], []]
>
> (3) [[- 1,2],[]]
> Type: List(List(Integer))
> (4) -> show(l)$ListUnparser(List INT, ListUnparser(INT, IntegerUnparser))
>
> (4) "[[-1,2,[]"
> Type: String
>
> Of course, I defined appropriate IntegerUnparser. And missing final
> "]" is because you forgot final assignment in the loop.
>
> Note: you need to use 'show(l)$P' where P is appropriate package.
> I suggest to build P when you analyze type descriptor (without
> type descriptor building T would be tricky).
>
To program forming this package P looks the same as the initial problem
of programming `show'.
(?)
In principle, I need to try and see now whether the categories Show and
Parse, and the related packages made after your design, can help my
parser
parseEvaluateShow : String -> String
written in Spad.
May be, this will work, I am not sure, so far.
But I hope to convince the Spad developers to introduce `extend' -- which
will make possible a most natural general style "by domain construction'.
Regards,
------
Sergei
[email protected]
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