to_num.rb

#! /usr/bin/env ruby

# File    : to_num.rb
# Author  : Patrik Wenger <paddor@gmail.com>
# Date    : 26th September 2008
# Version : 0.2
#
# It would be nice if there were fancy strings like %i, %f and %n for integers,
# floats and numbers, respectively. This library attempts to solve this problem.
#
# Use String#to_num to convert a number string to an Integer or Float object.
# If the string contains more than one number (separated by whitespaces),
# an Array of Integer and Float objects is returned.
# 
# Kernel#num can be used to achieve the same effect. Just pass it the string.
#
# Numeric#to_num returns itself.

class String
  def to_num
    if self[/\s/]
      strip.split(/\s+/).map {|n| n.to_num}
    else
      self["."] ? to_f : to_i 
    end
  end
end

module Kernel
  def num *input
    return nil if input.empty?
    if input.size > 1
      input.map {|n| n.to_num}
    else
      input.first.to_num
    end
  end
end

class Numeric
  def to_num; self end
end

if $0 == __FILE__

  require 'rubygems'
  require 'test/spec'

  # Have to use #be (same object ID) for Integers because 4 == 4.0.
  # Have to use #== (equal) for Floats because 4.0.object_id != 4.0.object_id.

  describe "String" do

    it "should convert a single integer to an integer" do
      "15" .to_num.should.be 15
      "501".to_num.should.be 501
      "-17".to_num.should.be -17
    end

    it "should convert a single float to a float" do
      "3.141".to_num.should == 3.141
      "-6.3" .to_num.should == -6.3
      "100.7".to_num.should == 100.7
    end

    it "should convert integer list strings to integers" do
      n = "3 -5 22".to_num
      n.class.should.be Array
      n[0].should.be 3
      n[1].should.be -5
      n[2].should.be 22
    end

    it "should convert float list strings to floats" do
      n = "3.3 4.0 -0.0 0.0".to_num
      n.class.should.be Array
      n[0].should == 3.3
      n[1].should == 4.0
      n[2].should == -0.0
    end

    it "should convert mixed list strings to integers and floats" do
      n = "45.12 300 -1 418.3496 1".to_num
      n.class.should.be Array
      n[0].should == 45.12
      n[1].should.be 300
      n[2].should.be -1
      n[3].should == 418.3496
      n[4].should.be 1
    end
  end

  describe "Kernel#num" do

    it "should handle single integers" do
      num(5).should.be 5
      num("666").should.be 666
      num("-555").should.be -555
    end

    it "should handle single floats" do
      num(3.1412).should == 3.1412
      num("45.45").should == 45.45
      num("-32.32").should == -32.32
    end

    it "should handle integer lists" do
      n = num "12", "-200", -6
      n.class.should.be Array
      n[0].should.be 12
      n[1].should.be -200
      n[2].should.be -6

      n = num *%w[687 23 -70]
      n.class.should.be Array
      n[0].should.be 687
      n[1].should.be 23
      n[2].should.be -70
    end

    it "should handle float lists" do
      n = num "0.3", "-14.7", 3.4, -12.0
      n.class.should.be Array
      n[0].should == 0.3
      n[1].should == -14.7
      n[2].should == 3.4
      n[3].should == -12.0

      n = num *%w[0.55 -5.2 1.2 -52.0]
      n.class.should.be Array
      n[0].should == 0.55
      n[1].should == -5.2
      n[2].should == 1.2
      n[3].should == -52.0
    end

    it "should handle list strings" do
      n = num "3.141 440 -2 305.96 3"
      n.class.should.be Array
      n[0].should == 3.141
      n[1].should.be 440
      n[2].should.be -2
      n[3].should == 305.96
      n[4].should.be 3
    end
  end

  describe "Numeric" do

    it "should return itself" do
      88.to_num.should.be 88
      4.3.to_num.should == 4.3
    end
  end
end