Question

I am working on my small newbie project. Project consist of two scripts. Script number1 is command line interface which recive parameters from user. Script number 2 creates Cartesian product and write it into text file. My idea is to make everything working without puting evertything into one file). When I try to use ‘load’ I get this error:”

Carthese_product.rb:3:in `<top (required)>': undefined local variable or method
`x_min' for main:Object (NameError)
        from D:/Cli_file.rb:25:in `load'
        from D:/Cli_file.rb:25:in `<main>'

Script1 (Cli_file.rb):

  require 'trollop'
  opts = Trollop::options do
  banner <<-EOS
Welcome to points generator!

Usage:
       test [options] <filenames>+
where [options] are:
EOS
    opt :x_min,             "Minimal value of X", :type => :int  
    opt :x_max,             "Maximal value of X", :type => :int 
    opt :y_min,            "Minimalna wartosc Y", :type => :int 
    opt :y_max,             "Maksymalna wartosc Y", :type => :int 
    opt :interval,          "Interval between points", :type => :int, :default => 1 
    opt :products_file,     "Name of products_file", :type => :string, :default =>    
                            "Products"     
  end

a= opts
x_min = a[:x_min]
x_max = a[:x_max]
y_min = a[:y_min] 
y_max = a[:y_max]
interval = a[:interval]
products_file = a[:products_file]
load 'Carthese_product.rb'

Script2 (Carthese_product.rb)

products = []

(x_min/interval..x_max/interval).each do |x|
(y_min/interval..y_max/interval).each do|y|
products << [x*interval,y*interval]
end
end
a = products.map.with_index{|w, i| "#{i+1} #{w[0].to_s} #{w[1].to_s} \n"}

aFile = File.new( products_file, "w+")
if aFile
    a.each{|x| aFile.write(x)}
else
puts "Something wrong!"
end

I know the easiest sollution is to put everything into one script, but for my educational purposes I want to find another way! Thanks for help & intrest!

Answer 1

You are attempting to use local variables to pass data from one script to the other. It doesn’t work because local variables, when defined at the top level, have file scope and thus cannot be accessed from separate files.

You must create a proper interface to your code so that you can reference it from other scripts. Create a module which implements Cartesian product:

# cartesian.rb

module Cartesian
  extend self

  def product(x_range, y_range, interval = 1)
    [].tap do |products|
      x_range.step interval do |x|
        y_range.step interval do |y|
          products << [x, y]
        end
      end
    end
  end
end

Now, require this file in your command line application executable, use the data given in the command line and write your output:

#/usr/bin/env ruby
require 'cartesian'

# Option parsing

Cartesian.product(x_min..x_max, y_min..y_max, interval).each do |product|
  puts "(#{product.first}, #{product.last})"
end

I recommend printing the program’s output to the standard output stream. That way, you can easily redirect the output to a file if you want to:

./cartesian-product $ARGUMENTS > product.list