On Thu, 3 Jan 2002, Billy Tanksley wrote:
> From: John Carter [mailto:john.carter@...]
>
> >In a sense Joy is about stopping NameQuakes.
> >In practically every other language every time a function is
> >defined, or a function is invoked, a Name Quake occurs.
> >By Name Quake I mean that the Name Space, the space of names
> >has shifted and changed. Old names perhaps no longer mean what
> >they did.
>
> Why does Joy avoid this?
>
> I think I might know what you're saying, possibly. Are you referring to the
> fact that currently defined local variables disappear, and a new set of
> locals gets defined? That's an interesting point. Yes, Joy does avoid
> that.
This is partly due to the absence of formal parameters in function
definitions. In lambda calculus based languages most such definitions
use lambda abstraction at least internally:
define foo(x y z) = ...x..y..z...
which is syntactic sugar for
define foo = lambda (x y z) ...x..y..z...
No matter which style of definition is used, any call to foo will
have to supply actual parameters, the values for x y z on that call.
In Joy there are no formal parameters, no environments of name/value
pairs.
But secondly, higher order functions such as map, fold, filter and so
on require a function parameter. In lambda calculus based languages
the actual parameter has to be a function given as a lambda abstraction
with formal parameters.
In Joy the actual parameter for higher order functions is a quotation,
and no formal parameters are needed for that.
I hope this helps.
- Manfred
>
> >John Carter Phone : (64)(3) 358 6639
>
> -Billy