From: "Peña, Botp" <botp@...>
Date: 2007-03-20T19:24:48+09:00
Subject: Re: C(++) For Loop Equivalents

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=0; i*j/2<maxNum; i++)
     4  # {
     5  #  //cool method stuff
     6  # }
     7  #---------------------------
     8
     9  # using normal while loop
    10  puts "using while..."
    11  j=20
    12  i=0
    13  maxnum=100
    14  while i*j/2 < maxnum do
    15     puts i
    16     i+=1
    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=0,incr=1)
    24     i = init
    25     loop do
    26        yield i
    27        i += 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