What is Expressiveness in a Computer Language

[Pascal Costanza]

Torben Ægidius Mogensen wrote:

> On a similar note, is a statically typed langauge more or less
> expressive than a dynamically typed language?  Some would say less, as
> you can write programs in a dynamically typed language that you can't
> compile in a statically typed language (without a lot of encoding),
> whereas the converse isn't true.

It's important to get the levels right here: A programming language with 
a rich static type system is more expressive at the type level, but less 
expressive at the base level (for some useful notion of expressiveness ;).

> However, I think this is misleading,
> as it ignores the feedback issue: It takes longer for the average
> programmer to get the program working in the dynamically typed
> language.

This doesn't seem to capture what I hear from Haskell programmers who 
say that it typically takes quite a while to convince the Haskell 
compiler to accept their programs. (They perceive this to be worthwhile 
because of some benefits wrt correctness they claim to get in return.)


Pascal

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