Re: [stack] Classifying languages by how they handle operands

Don Groves <[email protected]> wrote:
> It occurred to me recently that one way to differentiate programming
> languages is by how they handle operands.

Sure thing -- sensible.

> Lisp and its cousins use operands only once, placing them in a
> structure preceded by an operator, (+ a b c) , effectively combining
> their passing and evaluation.

Let me add a word to your description:
Lisp and its cousins place operands them in a *lexical* structure
preceded by an operator, (+ a b c) , effectively combining their
passing and evaluation.

I also deleted "use operands only once", since I don't know what you
mean by that. (What did you mean?)

> The languages of interest to this group place operands in a structure
> followed by a sequence of operators, (a b c) + +, which also combines
> passing and evaluation.

...and here my modification is to stress that the structure is a *semantic* one.

The major difference is that the lexical structure is constrained to
the medium of the language -- one-dimensional text parsed into a tree.
A semantic structure can be more complex -- the operand flow for a
stack language is a digraph rather than a tree.

There are pros and cons to both.

> While admittedly low level, is this concept worthy of further
> discussion? Has it been discussed before, either here or elsewhere?

I believe Manfred looked at it before... I can't recall which paper, though.

> Don

-Wm