Martin Baker wrote:
>
> Also I find SExpressions and their associated pretends quite evil (I
> know there are a few cases where we have to use them). One of the
> advantages of moving to SPAD is that it is more strongly typed, but
> using SExpressions+pretends seems to turn it back into a loosely typed
> language again. This may not be a problem for you guys, if you know what
> types to expect, but for me it would lead to runtime errors which are
> harder to find than compile time errors. I would find it much easier to
> go directly to high level code and debug that.
Just to make clear what the direction is: formaters in FriCAS 1.2.2
(Formula, TeX, Texmacs, MathML and HTML) contain 37 pretends and
54 '$Lisp' calls. Trunk today has 13 pretends in formaters + OFTOOL
and 31 '$Lisp' calls. AFAICS all pretend and '$Lisp' calls related
to OutputForm are in OFTOOL. Most of remaining '$Lisp' calls are
debugging printouts. So, the result is far from ideal, but IMHO
we got significant improvement with relatively little effort.
Also, I when SExpression is openly used, then it should be enough
to use exported interface of SExpression, without any pretends.
Pretends appear when we want to have stronger typing having
SExpression as representation.
--
Waldek Hebisch
[email protected]
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