Re: RAD vs. performance

Yet Another Dan wrote:
My impression is that a dynamically typed
interpreter is good for RAD, and a statically typed compiler generates
good performance.

Static typing also finds bugs. If you want your rapidly-developed
application to work then this is important.

CL can be either interpreted or compiled, and is
dynamically typed but has static "advisory" typing for final optimization.

Yet CLs performance is far worse than that of most modern, statically-typed
languages (e.g. MLs). Putting more effort into optimisation is no
substitute for designing a language that will run fast.

Is there any other language that does something like that?

All languages do "something like that". The problem with your question is
really that there is a blurry line between dynamic and static typing. There
are only "conventional beliefs". For example, dynamic typing is a special
case of static typing where no type checking is done at compile time.
Consequently, there is a range of static typing going from almost-dynamic
to very static. Java and SML are both considered to be "statically typed"
and, yet, Java code does a lot more run-time checking.

Switches
between interpreting and compiling, and between dynamic and static typing?

Many languages have both interpreted and compiled implementations.

There are OCaml macros to implement dynamic typing but they are just an
academic curiosity - OCaml programmers rarely (if ever) want to ditch
static typing. However, they often want to box values into variant type
constructors.

Is Lisp the only language with adjustabe typing and execution?

All languages have adjustable typing and execution. AFAIK, it is
prohibitively difficult to reap the rewards of static typing (particularly
performance) with an implementation within Lisp. Consequently, I suspect
such things are also an academic curiosity.

--
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
http://www.ffconsultancy.com/products/ocaml_for_scientists/chapter1.html
.

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