From: Albert Ng <twinwing@...>
Date: 2007-03-21T05:45:25+09:00
Subject: Re: C(++) For Loop Equivalents

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Is there any reason you can't use the syntactical sugar "for"? Or maybe
construct a range:

(i...((maxNum*2)/j) ).each_with_index do |stuff| end

On 3/20/07, Michael W. Ryder <_mwryder@worldnet.att.net> wrote:
>
> Pe=F1a wrote:
> > From: Michael W. Ryder [mailto:_mwryder@worldnet.att.net] :
> >
> > # He would need to initialize i before your code as it could be
> > # any value,
> > # not just 0.  By the same token the increment could be any number, not
> > # just 1.
> >
> > fwiw, this is a simple example (intended for nubies only).
> >
> > C:\family\ruby>cat -n test.rb
> >      1  #---------------------------
> >      2  #emulate c++ for (the better)
> >      3  #for(int i=3D0; i*j/2<maxNum; i++)
> >      4  # {
> >      5  #  //cool method stuff
> >      6  # }
> >      7  #---------------------------
> >      8
> >      9  # using normal while loop
> >     10  puts "using while..."
> >     11  j=3D20
> >     12  i=3D0
> >     13  maxnum=3D100
> >     14  while i*j/2 < maxnum do
> >     15     puts i
> >     16     i+=3D1
> >     17  end
> >     18
> >     19  # let's make our own for() and call it for_simple :)
> >     20  # note, there's no condition here
> >     21  # we're leaving it up to yield/blocks since that
> >     22  # is the ideal way, imho
> >     23  def for_simple (init=3D0,incr=3D1)
> >     24     i =3D init
> >     25     loop do
> >     26        yield i
> >     27        i +=3D incr
> >     28     end
> >     29  end
> >     30
> >     31  # now let's test it
> >     32  puts <<TEXT
> >     33  Test I.
> >     34  using our own simple for()...  note advantage,
> >     35  we don't need to track the counter...
> >     36  TEXT
> >     37
> >     38  for_simple do |i|
> >     39     break unless i*j/2 < maxnum
> >     40     puts i
> >     41  end
> >     42
> >     43  puts <<TEXT
> >     44  Test II.
> >     45  here we initialize to 2 and increment by 2
> >     46  again, we don't need to track the counter...
> >     47  TEXT
> >     48
> >     49  for_simple(2,2) do |i|
> >     50     break unless i*j/2 < maxnum
> >     51     puts i
> >     52  end
> >     53
> >     54  puts <<TEXT
> >     55  Test III.
> >     56  again, here we initialize to 200 and decrement by 20
> >     57  again, we don't need to track the counter...
> >     58  and note, we change keyword unless to if
> >     59  ruby just simply rocks..
> >     60  TEXT
> >     61
> >     62  for_simple(200,-20) do |i|
> >     63     break if i*j/2 < maxnum
> >     64     puts i
> >     65  end
> >
> > C:\family\ruby>ruby test.rb
> > using while...
> > 0
> > 1
> > 2
> > 3
> > 4
> > 5
> > 6
> > 7
> > 8
> > 9
> > Test I.
> > using our own simple for()...  note advantage,
> > we don't need to track the counter...
> > 0
> > 1
> > 2
> > 3
> > 4
> > 5
> > 6
> > 7
> > 8
> > 9
> > Test II.
> > here we initialize to 2 and increment by 2
> > again, we don't need to track the counter...
> > 2
> > 4
> > 6
> > 8
> > Test III.
> > again, here we initialize to 200 and decrement by 20
> > again, we don't need to track the counter...
> > and note, we change keyword unless to if
> > ruby just simply rocks..
> > 200
> > 180
> > 160
> > 140
> > 120
> > 100
> > 80
> > 60
> > 40
> > 20
> >
> > C:\family\ruby>
> >
> > Hth.
> > kind regards -botp
> >
> >
>
> Now is it possible, like in Scheme, to assign a variable to a string and
> have Ruby evaluate the string?  For example, f =3D "i*j/2".  This would
> allow one to make a more generic version of your methods.  Ideally you
> would have for_opt (i=3D0, f, inc=3D1) and have the method evaluate each =
of
> the variables if necessary.  This would allow one to copy working C code
> without having to remember to do a lot of extraneous coding.
>
>
>

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