[REBOL] rebol weak points (i think) Re:(3)
From: brian:hawley:bigfoot at: 9-Sep-2000 10:05
[rishi--picostar--com] wrote:
>no. The Math/Pie you have created is an instance variable not a static
>variable. It is associated with an instance of the class, not the class
>itself. A static variable means that there is a single copy of this variable
>associated with class itself. You do not need to instantiate a class to use
>static variable.
You have it backwards. REBOL doesn't have classes. OOP in REBOL is
prototype/delegation based, like Self, NewtonScript or JavaScript -
not class-based like C++, Smalltalk or Java.
Objects in REBOL are all unique. Their behavior is defined within
themselves using static variables, rather than through their class.
They are created from prototypes, not classes. Constructors are just
functions. You don't inherit the features of a class, you call them
directly - this is known as delegation. All fields are static - any
instance
objects you create call the "class" objects directly.
This style of object-oriented programming, used properly, can be more
efficient than class-based programming. If you really need classes
they're a simple design pattern away.
>For example:
>
>make-circle: make func [
> radius
> /local blah-blah-blah
> /static num_circles ;let's say this is how you create static var.
>] [
> num_circles: num_circles + 1 ;this may not be correct but you get the
>idea...
> return make object! [
> ;object code goes here
> ]
>]
There are techniques for making persistent values in functions -
most of them are arcane (but fun). Functions don't have static
variables as such but you can embed structured data in the code
of the function.
Most of the time it's better to use objects. Try this:
circle-class: make object! [
num-circles: 0
new: func [value [number!]] [
num-circles: num-circles + 1
make object! compose [
class: (self)
radius: value
num-circles: func [] [class/num-circles]
]
]
]
(skipped a little...)
>The main disadvantage of having static variables is that perhaps it is an
>unnecessary complication. But I don't think so. Maybe because I come from
>java/javascript background. I'm still wondering though if there is a way to
>have static variables that I don't know.
It's interesting that you mention Java and JavaScript in the same
sentence here. Java is class-based like C++. JavaScript is more
like REBOL - all variables are static, constructor functions,
class factory objects instead of classes. The object model of
JavaScript has been traditionally confusing for those who think
OOP is only class-based...
>Regardless, the main problem that I wonder about is if rebol is suited for
>modular programming where people reuse other people's functions/code. Since
>everything is either global or local, it seems as though it would be
>unnatural to use rebol in this way. Java has packages and stuff...
Coming from a background of Oberon, Delphi and such (among many
others) I'd have to agree. Fortunately RT has listened :)
Look at this: http://www.rebol.com/reps/rep002.html
It's a little outdated - many changes have purportedly been made
already but they haven't been codified yet. I gather security
support will be much improved. Still, it's a taste of things to
come. I'm looking forward to it :)
>Perhaps I am not thinking straight and have too much java in my
>blood (which I have been doing to much of lately and finally got
>sick of all the abstractions that got in the way of doing simple
>stuff!!)
Tell me about it :(
I'm having the opposite problem. I just got put on a project that
is being done with ColdFusion, a web template language like ASP. I
can't go 5 minutes without running into some limitation that would
be trivial to overcome with REBOL. Maybe I can do the next round
with REBOL/Serve when it comes out...
Brian
