john@paloalto:~/App_Academy/learn_ruby/01_temperature$ ls
index.html  temperature.rb  temperature_spec.rb
john@paloalto:~/App_Academy/learn_ruby/01_temperature$ cat temperature.rb
def round_to(x)
  (self * 10**x).round.to_f / 10**x
end

def ftoc(num)
  return ((num - 32) / 1.8).round_to(1)
end

def ctof(num)
  return ((num *1.8) +32).round_to(1)
end
john@paloalto:~/App_Academy/learn_ruby/01_temperature$ cat temperature_spec.rb
# # Topics:
# * functions
# * floating-point math
#
# # Hints
#
# Remember that one degree fahrenheit is 5/9 of one degree celsius, and that the freezing point of water is 0 degrees celsius but 32 degrees fahrenheit.
#
# In integer math, there **are no fractions**. So if you are using integer literals, you will be using integer math, which means, for example...
#
#    1 / 2 => 0
#
# In floating point math, there **are** fractions. So...
#
#    1.0 / 2.0 => 0.5
#

require "temperature"

describe "temperature conversion functions" do

  describe "#ftoc" do

    it "converts freezing temperature" do
      ftoc(32).should == 0
    end

    it "converts boiling temperature" do
      ftoc(212).should == 100
    end

    it "converts body temperature" do
      ftoc(98.6).should == 37
    end

    it "converts arbitrary temperature" do
      ftoc(68).should == 20
    end

  end

  describe "#ctof" do

    it "converts freezing temperature" do
      ctof(0).should == 32
    end

    it "converts boiling temperature" do
      ctof(100).should == 212
    end

    it "converts arbitrary temperature" do
      ctof(20).should == 68
    end

    it "converts body temperature" do
      ctof(37).should be_within(0.1).of(98.6)
      # Why do we need to use be_within?
      # See http://www.ruby-forum.com/topic/169330
      # and http://en.wikipedia.org/wiki/IEEE_754-2008
      # and http://en.wikipedia.org/wiki/Double_precision_floating-point_format
      # Also, try "puts 0.5 - 0.4 - 0.1" -- pretty crazy, right?
    end

  end

end
john@paloalto:~/App_Academy/learn_ruby/01_temperature$ rake
(in /home/john/App_Academy/learn_ruby)

temperature conversion functions
  #ftoc
    converts freezing temperature (FAILED - 1)

Failures:

  1) temperature conversion functions#ftoc converts freezing temperature
     Failure/Error: ftoc(32).should == 0
     NoMethodError:
       private method `round_to' called for 0.0:Float
     # ./01_temperature/temperature.rb:6:in `ftoc'
     # ./01_temperature/temperature_spec.rb:25:in `block (3 levels) in <top (required)>'

Finished in 0.00081 seconds
1 example, 1 failure

Failed examples:

rspec ./01_temperature/temperature_spec.rb:24 # temperature conversion functions#ftoc converts freezing temperature
rake aborted!
/usr/bin/ruby1.9.1 -S rspec /home/john/App_Academy/learn_ruby/01_temperature/temperature_spec.rb -I/home/john/App_Academy/learn_ruby/01_temperature -I/home/john/App_Academy/learn_ruby/01_temperature/solution -f documentation -r ./rspec_config failed

Tasks: TOP => default => spec
(See full trace by running task with --trace)
john@paloalto:~/App_Academy/learn_ruby/01_temperature$