OpenEuphoria

Re: Eu improvements (part 4)

• Posted by James W Hofmann <jhofmann at ucsc.edu> Jan 06, 2007
• 795 views

Karl Bochert wrote:
> The intention is to access the elements by name. If you want to access by
> index, you should use a plain unstructured sequence.

In that case, please don't call them "sequences." That is
misleading. Sequence means indexing to me. And "structured" is
not very meaningful except in relation to C structs, or the practice
of "structured programming," which is mostly about flow of execution
but when taken in this context led me to believe it must have been
about type checking(a practice that came into vogue at the same time
as structured programming).

Hence, my remarks on typing and indexing. I don't have any major
problem with the concepts, but I do disagree with how they are
presented.
I think it would be a good idea to extend type to support
these things. So I will propose something and see if you like it.

You could have two syntaxes:

type Point(sequence s) -- classic syntax
    ...
    return checkval
end type

type Point is -- like SS
    atom x,y
    (where)
    ...
    (requiring)
    ...
    return checkval
end type

1. "Is" now tells us that Point is going to contain several 
variables(ignoring their internal representation; whether it
should be accessable as a sequence or not is tangential to
the major functionality of named access)

2. "Where" lets us initialize these variables each type we
instantiate a Point. This is optional, hence the (), which would
not appear in real code.

The "Point.x = 5" example of setting the initialization is still
valid, but I think "where" is a bit cleaner since it keeps that 
inside the same code block. 

3. "Requiring" is the original use of type, the checking
functionality. But since we aren't using a sequence representation
there is no reason for a parameter to be passed. Instead we would
only refer to the variables that "is" declared, in this case x and
y. Note that there would be two checks, one for is and one for
requiring.

The "extends" syntax can apply as in your SS proposal, with
the "where" and "requiring" keywords causing an override of the
original declaration.