[plt-scheme] Why do folks implement *dynamically* typed languages?

From: Carl Eastlund (cce at ccs.neu.edu)
Date: Wed May 30 00:58:45 EDT 2007

Which way are you asking?  Your subject line asks one question, but
your content asks another.  I guess you are trying to ask "why dynamic

Here's why I like dynamically typed languages: because types are far
too important too me.  I'm not going to let some tyrannical type
checker decide in advance what type system I'm going to use for all
programs.  I'm going to use whatever notion of types is appropriate
for my current task, and check as much of that statically as I can.
If ML's type checker, or Haskell's type checker, or Java's type
checker can't verify my invariants, or worse reject my program as an
error - all static type checkers are guaranteed to reject some 100%
correct programs as errors - I'd be out of luck in those languages.
I'm always in luck with Scheme.

It puts a lot of responsibility on me to get the system right, but I
can live with that.

On 5/29/07, Grant Rettke <grettke at acm.org> wrote:
> Hi folks,
> Why do people design dynamically typed (DL) languages over statically
> typed languages (Sl)?
> In the case of Lisp, it seems obvious, metaprogramming. That said, you
> can metaprogram in SLs, so maybe it is not so obvious.
> Are there any good papers or books on this matter?

Carl Eastlund

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