On Jul 3, 2006, at 19:27, Dark A. wrote:
I’m looping through firstarray.each do |x|
go through some blocks. At some point, either the start of the outter
array or somewhere down in the conditional statements I need to find
out if elements of firstarray are in secondarray. The only way I can
fathom doing this right now is by starting another loop, i.e.
secondarray.each do |y|. Problem is this seems to create constant
problems where the outter loop / [0] element is going through the
entire inner loop before proceeding on. to it’s next element. Maybe
as someone suggested earlier today to me, to use break. Haven’t had
much luck with that yet.
If you don’t want to use loops at all, you could use the intersection
operator:
overlap = firstarray & secondarray
If you do want to use loops (which would be good practice for you),
then just be careful to remember what each loop is doing. While
using include? or the intersection operator wouldn’t hurt anything,
given your trouble with nesting loops it’s probably good practice to
learn how to do them properly - they’re an incredibly common
construct in programming, and if you don’t learn how to build them
for something simple you could get very stuck later on. Even your
simple file comparison example wouldn’t work using include?, since
the filenames include different directories.
The basic idea you should remember is that you can write the inner
loop as if it were a normal loop working with a single variable. For
example, if the outer loop is “firstarray.each do |first|” then you
can write the inner loop as if you had this:
first = 1
secondarray.each do |second|
do things with first and second here.
end
Here’s a simple example which tells you exactly what it’s doing:
firstarray = [1, 2, 3]
secondarray = [1, 3, 5]
overlap = []
firstarray.each do |first|
puts “Outer loop setting first = #{first}”
we want to compare first to everything in the second array:
secondarray.each do |second|
puts “\tInner loop setting second = #{second}”
print “\tComparing #{first} to #{second}…”
if first == second
puts “matched!”
# do what we need to when we find a match
overlap.push(first)
# if you know there’s a max of 1 match,
# you could put a break here to stop looking
# for more matches.
else
puts “no match.”
end
end
puts “\tInner loop finished.”
end
puts “Outer loop finished.”
puts overlap
matthew smillie.