What is Expressiveness in a Computer Language

Rob Thorpe robert.thorpe at antenova.com
Wed Jun 14 17:12:12 CEST 2006

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.  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.

>From the point of view purely of expressiveness I'd say it's rather

If a language can express constraints of one kind that is an increase
in expressiveness.
If a language requires constraint to be in one particular way thats a
decrease in expressiveness.

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

This meets my experience of what useful in practice too, static typing
for everything is painful for writing simple code.  Pure dynamic typing
is painful when writing complex code because it makes impossible a
layer of error checking that could otherwise be useful.

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