What is Expressiveness in a Computer Language

Matthias Blume find at my.address.elsewhere
Mon Jun 19 21:21:19 CEST 2006

Pascal Costanza <pc at p-cos.net> writes:

> Matthias Blume wrote:
>> "Rob Thorpe" <robert.thorpe at antenova.com> writes:
>>> I don't think dynamic typing is that nebulous.  I remember this being
>>> discussed elsewhere some time ago, I'll post the same reply I did then
>>> ..
>>> A language is statically typed if a variable has a property - called
>>> it's type - attached to it, and given it's type it can only represent
>>> values defined by a certain class.
>> By this definition, all languages are statically typed (by making
>> that
>> "certain class" the set of all values).  Moreover, this "definition",
>> when read the way you probably wanted it to be read, requires some
>> considerable stretch to accommodate existing static type systems such
>> as F_\omega.
>> Perhaps better: A language is statically typed if its definition
>> includes (or ever better: is based on) a static type system, i.e., a
>> static semantics with typing judgments derivable by typing rules.
>> Usually typing judgmets associate program phrases ("expressions") with
>> types given a typing environment.
> How does your definition exclude the trivial type system in which the
> only typing judgment states that every expression is acceptable?

It does not.

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