From: "Peña, Botp" <botp@...>
Date: 2007-01-18T17:24:02+09:00
Subject: Re: printing 2 dimensionl hash problem

From: Krekna Mektek [mailto:krekna@gmail.com] :
#----------------------------------------------------------
#  @h.each do |key,value|
#       print key, " is ", value.each {|x| print x, " -- " }, "\n"
# 
# The print is strange, becuase it looks like this now:
# 
# 1 -- 2 -- 3 -- A is 123
# 4 -- 5 -- 6 -- B is 456
#
# 1. How come the code block is executed first
#----------------------------------------------------------

print expects to print a value of the expression (of course). so before prints does the writing, it has to get the value first.

#----------------------------------------------------------
# 2. After that the key and value is printed, however, I don't see the
print for the values here (except for the print in de the code block,
which was executed already).
#----------------------------------------------------------

"value.each {...} " is an expression that returns a value, in this case the array "value". that expression however will perform *first a {|x| print x, "---"} for every element x in array "value".

eg,


C:\temp\rubygems-0.9.1>cat test.rb

h = {"A" => [1,2,3], "B" =>[4,5,6]}

puts "sample 1"
h.each do |key,value|
   print key, " is "
   value.each {|x| print x, " -- " }
   print "\n"
end
puts
puts "sample 2"
h.each do |key,value|
   puts "#{key} is #{value.join(' -- ')}"
end


C:\temp\rubygems-0.9.1>ruby test.rb
sample 1
A is 1 -- 2 -- 3 --
B is 4 -- 5 -- 6 --

sample 2
A is 1 -- 2 -- 3
B is 4 -- 5 -- 6

hth.
kind regards -botp