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convert.rb
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convert.rb
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#!/usr/bin/env ruby
# convert - a simple unit converter
# Copyright (C) 2008 Benjamin Ferrari
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
# This class does simple unit convertions
# the constructor expects an io object that contains a simple rules of
# the form sourceunit targetunit factor. All lines in a rules file that
# start with the character '#' are comments and will be ignored.
#
# For example, a rules file could look like this:
# km m 1000
# in cm 2.54
#
# this will automatically create 4 methods in the Converter:
# km_to_m, m_to_km, in_to_cm and cm_to_in
#
#Example: convert km m 10
#output: 10000
class Converter
#create a method that sends the message 'op' with the argument
#'value' to the first argument of the function
def self.create_method from, to, op, factor
name = "#{from}_to_#{to}".to_sym
define_method(name) do |arg|
arg.send(op,factor.to_f)
end
end
def initialize(io)
@io = io
#read through all the rules and create 2
#methods for each rule (from unit1 to unit2 and vice versa)
@io.readlines.each do |line|
#ignore lines that start with # (comments in rules file)
next if line =~ /^ +\#.*$/
sunit, tunit, factor = line.split(/ +/)
Converter.create_method sunit, tunit, "*", factor
Converter.create_method tunit, sunit, "/", factor
end
end
end
if $0 == __FILE__
from,to,factor = ARGV
puts Converter.new(File.new("rules")).send("#{from}_to_#{to}",factor.to_f)
end