Re: What's so great about lisp?

Jon Harrop <usenet@xxxxxxxxxxxxxx> writes:

> Lars Brinkhoff wrote:
> > Or, "how likely is there to be an error, not detectable by a type
> > system, in your algorithm or its implementation (be it sorting or
> > otherwise)?". Not unlikely, I'd say.
>
> From my experience, that is very true when dynamic typing is required, e.g.
> my GUI code. However, there are many places (most of my code) where I think
> the type checker is likely to catch most (>50%?) errors. I watched myself
> (?!) writing a rewrite interpreter last night and the OCaml and SML type
> checkers literally caught all of my errors (it worked perfectly the first
> time it ran).

Yikes, do you not see what you just said here?!?! For normal code,
dynamic typing helps you get your work done -- but for building
interpreters for general-purpose languages, the ML type system is
really helpful. So, ML is good for implementing ML, and things like
ML, and Lisp is good for everything else?!?! Why bother with ML then?

For the record, yes, I found static type checking to be very helpful
when writing a CPS-transforming CL-to-CL compiler. It found 80% of my
errors, and runtime type assertions found the others. The type
checking infrastructure cost me 120 lines of CL. Just like the
ability to write custom interpreters, the ability to write
domain-specific type checkers is an important tool -- and once you
have that, and a language that supports you in it (like, eg, CL), you
always have custom type systems available. The only limit is your
ability to read type theory papers :-)

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