What is Expressiveness in a Computer Language

[Joachim Durchholz]

Rob Thorpe schrieb:
> 
> If a language can express constraints of one kind that is an increase
> in expressiveness.

Agreed.

> If a language requires constraint to be in one particular way thats a
> decrease in expressiveness.

Unless alternatives would be redundant.
Having redundant ways to express the same thing doesn't make a language 
more or less expressive (but programs written in it become more 
difficult to maintain).

> So I would say languages that can be statically typed and can be
> dynamically typed are the most expressive.  Languages that require
> static typing or are dynamic but cannot express static typing are less
> expressive.

Note that this is a different definition of expressiveness.
(The term is very diffuse...)

I think Felleisen's paper defines something that should be termed 
"conciseness".
Whether there's a way to express constraints or other static properties 
of the software is something different. I don't have a good word for it, 
but "expressiveness" covers too much for my taste to really fit.

Regards,
Jo