Re: Ruby and OO (fwd)

[Scott McKay <address@hidden>]

At 11:51 AM 11/29/01, Eli Collins wrote:

> > Quite honestly, I would never guess that the following fragments come from
> > the same language:

Thanks for your reply!

> > - upto(100) { |i| puts i }
> > - print ARGF.grep /Ruby/
> > - @numMeetings.times { twoRatsMeet if moreThanOneRatLeft }
> >
> > I honestly can't figure out what any of these fragments means at a deep
> > level.  For example,
> >   - Why isn't the first 100.upto { |i| puts i }
>
>Like any language you have to spend a little time looking at the
>syntax in order to understand it. The syntax is "1.upto(100)" instead
>of "100.upto" because you want to count from 1 to 100, you could as
>easily do "x.upto(y)" where x and y are variables.  "x.upto(y) { |i|
>.. }" is equivalent to "for (i=x;  x<=y; i++) { ... }"  Numeric types
>(objects) have an upto method (and others) so you don't need for
>loops. In ruby, iterators are implemented using blocks and are used
>extensively.
>
> >   - What's with the vertical bars around the i?
>
>Thats how you delminate the loop variable.
>
> >   - What's the "receiver" for puts?
>
>"puts" is a print statement. maybe this is more clear:
>
>10.upto(100) { |i|
>         puts i
>}
>
>will print 10 to 100. Check out more on blocks. "puts i" is actually a
>block of code which is being passed to the upto method. Understanding
>ruby iterators is not as easy as understanding java iterators, but
>they are more powerful. imho this is a clunky way to print out a list
>of integers:
>
>for (ListIterator li = alist.listIterator(); i.hasNext();) {
>         Integer i = (Integer)li.next();
>         System.out.println(i);
>}
>
>in ruby this is:
>
>list.each { |i|
>         puts i
>}

For your entertainment, I'm including some Dylan examples.

In Dylan, given the function 'print' to print an object, then if 'list' is 
bound
to a collection and you could use this:
   do(print, list);

You could print out a range like this:
   do(print, range(from: 10, to: 100));

That is, the function 'do' takes two arguments: the second is a collection,
and the first is a function to apply to each element of the collection.

>This, to me, is easier to read. This is of course one of the nice
>things about scripting languages (the perl and python are similar
>though not oo, not that oo is the end all be all, its just the way
>ruby does things).
>
> >   - What's the "receiver" for print?
>
>print is similar to puts
>
> >   - What on earth is "@"?
>
>This deliminates a class member variable. Here's an example class:
>
>class SomeObject
>   attr_reader :memberVar
>   attr_writer :memberVar
>
>   def initialize()
>     @memberVar = 10
>   end
>
>   def isMemberVarBig?
>     return @memberVar > 100
>   end
>end

In Dylan,

   define class <some-object> (<object>)
       slot member-var = 10;
   end;

   define method member-var-big? (o :: <some-object>)
     o.member-bar > 100
   end;


>attr_read/writer is an easier way of defining getters/setters. the
>second method is the same as a getter, it just illustrates using the
>member variable (you don't need to write the return because the
>value of the last expression executed is always returned).
>
> >   - I guess I understand the 'if', maybe...
> >
> > I read the introductory material and didn't feel any more enlightened,
> > quite honestly.  Of course, I never could read Smalltalk, either...
>
>To each their own :)  Ruby definetly goes about doing some things
>differently.
>
> >
> > Some people also think that terseness in the language is a feature.
> > I myself don't buy that.  I don't believe in verbose, either, as it 
> happens.
> >
>
>I think terseness is a feature only if it makes the code easier to
>read. To me terseness/verbocity is not the issue, ease of reading is.

Agreed.