RE: Eval - Pro's and Con's (was Re: Dylan rather than CL -- why?)

[Stuart Watt <S.N.K.Watt@open.ac.uk>]

Stavros Macrakis writes:
>There are legitimate applications for eval

If Dylan is intended for C++/Object Pascal people, eval is mostly redundant,
and it is easy to add something like a Scheme interpreter if required.

In Procyon Common Lisp, eval is never delivered, print, format, and read are
optional, and each makes 100-150K difference to the size of the delivered
system. In a typical application, only a subset of read is required (such as
read-line and custom code), and this is much smaller. The same goes for print
(using write-string). 

I think Dylan has its standards just about right here, but then, I never liked
eval. There is a big issue hovering below the surface here. eval is used for
REP loops, and REP loops are part of things like "command-line" interfaces, but
not usually anything to do with GUIs. I wouldn't want to see eval put in to
help develop the wrong kind of system. 

>Perhaps you are confusing syntax with the ability to manipulate syntax
>trees as data structures?

Surely this is more the responsibility of a Dylan version of lex/yacc; surely
again an external library for this kind of stuff is called for. It could even
provide good old read into the bargain. 

Regards, Stuart Watt
Human Cognition Research Laboratory,
The Open University, Walton Hall, Milton Keynes, MK7 6AA. UK.