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comp.lang.ruby

Re: internal iterators in ruby

Geert Fannes

6/2/2005 8:28:00 AM

Hello, the following code can iterate over any number of arrays and has
both the each and collect method implemented. You find some example
usage at the end of the code.
Greetings,
Geert Fannes.

#begin code
class GZipExc < Exception
def initialize(problem="")
@ExcStr||="A GZipExc occured"
super(problem)
end
end

class GZip
include Enumerable

def initialize(*arg)
raise GZipExc.new("You cannot pass a block to GZip.new. Maybe you
forgot .each or something.") if block_given?
@arrays=Array.new
@minLength=nil
if TrueClass===arg.first
arg.shift
arg.each do |a|
a=a.dup if @arrays.include?(a)
@arrays.push(a)
if @minLength
@minLength=a.length if a.length<@minLength
else
@minLength=a.length
end
end
else
arg.each do |a|
a=a.dup if @arrays.include?(a)
@arrays.push(a)
if @minLength
raise GZipExc.new("Different lengths found: #{@minLength} !=
#{a.length}.") if a.length!=@minLength
else
@minLength=a.length
end
end
end
end

def GZip.minLen(*arg)
new(true,*arg)
end

def each
(0...@minLength).each {|i| yield(@arrays.collect {|a| a[i]})}
end

def each_with_index
(0...@minLength).each {|i| yield((@arrays.collect {|a| a[i]}) << i)}
end

def all?
bOK=true
(0...@minLength).each do |i|
if !yield(@arrays.collect {|a| a[i]})
bOK=false
break
end
end
return bOK
end

def delete_if
ix=0
(0...@minLength).each do |i|
if yield(@arrays.collect {|a| a[ix]})
@arrays.each{|a| a.delete_at(ix)}
else
ix+=1
end
end
return self
end
end

if $0==__FILE__
a=[1,2,3]
b=[4,5,6]
c=[7,8,9]
GZip.new(a,b,c).each do |aa,bb,cc|
print aa,bb,cc,"\n"
end
b.push(7)
begin
GZip.new(a,b).each do |aa,bb|
print aa,bb,"\n"
end
rescue GZipExc
puts "I rescued the exception"
else
puts "ERROR::i did not catch the expected exception"
end
GZip.minLen(a,b).each do |aa,bb|
print aa,bb,"\n"
end
b.pop
d=GZip.new(a,b,c).collect do |aa,bb,cc|
[aa,bb,cc]
end
d.each do |dd|
puts dd.join(' ')
end
end
#end code

-----Original Message-----
From: Navya Amerineni [mailto:navyaamerineni@yahoo.com]
Sent: 02 June 2005 05:39
To: ruby-talk ML
Subject: internal iterators in ruby

Hi,

I read that it is difficult to iterate over two
collections in paralell using ruby's internal
iterators.
can any one explain me indetail why it is so..

thanks in advance

Navya




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1 Answer

Robert Klemme

6/2/2005 10:45:00 AM

0

Geert Fannes wrote:
> Hello, the following code can iterate over any number of arrays and
> has both the each and collect method implemented. You find some
> example usage at the end of the code.
> Greetings,
> Geert Fannes.

<snip long code/>

You code works only for arrays, but it's quite efficient.

This works for all Enumerable types, is less efficient - and it's part of
the std lib:

http://www.ruby-doc.org/stdlib/libdoc/generator/rdoc/classes/SyncEnume...

Know your standard libs... :-)

Kind regards

robert