Re: [stack] Parameters: ordered versus named

On 9/8/07, Don Groves <[email protected]> wrote:
> On Sep 8, 2007, at 19:08 , Christopher Diggins wrote:
>
> >> That's because concatenative languages, in general, don't hide
> >> information; but I agree that if you do hide information, you have to
> >> pay the price. I was also illustrating that the price to be paid
> >> wasn't what you thought it was -- Cat pays the price not by being
> >> more
> >> primitive, but by having a sophisticated static type inference system
> >> (which can, of course, slow some things down, but is undeniably NOT
> >> primitive and is a desirable feature for many purposes).
> >
> > A static type inference system certainly slows down compilation, but
> > all things given equal should speed up runtime execution because it
> > removes the need for runtime checks. Furthermore a static type
> > inference system makes it easier to optimize code, because you can
> > take advantage of properties that you have elucidated about the
> > runtime behaviour. However, every implementation is different.
> >
> > A simple static type system has the disadvantage that typed terms will
> > disallow unbalanced stacks. You can't say things like:
> >
> > if_tuesday [1] [1 2] ifte // does stack have one or two elements?
> >
> > - Christopher
>
> Clearly, I need to learn more about type systems. Here's the Catenate
> code implementing ifte, what kind of type system does this represent?
>
> int ifte_() { // [f1] [f2] T|F ifte => (results of f1 if T)
> // => (results of f2 if F)
> if (depth < 3) {
> StackError("ifte", "underflow");
> return OK;
> }
> if (!islist(Y)) {
> printf("\nifte: Y must be a list\n");
> return UNKNOWN;
> }
> if (!islist(Z)) {
> printf("\nifte: Z must be a list\n");
> return UNKNOWN;
> }
> if (X == TRUE) { // T|F = true?
> drop_(); drop_(); // (y) drop T and 'else' part (f2)
> id_(); // execute 'then' part
> }
> else { // (n) false
> drop_(); swap_(); drop_(); // drop F and 'then' part (f1)
> id_(); // execute 'else' part
> }
> return OK;
> }
> --
> Don

This is an example of a runtime checked language, also called a
dynamically typed language, though some theorists object to the term
dynamic typing. Personally I have no qualms with it.

-D