Exercise: Print out a pretty right triangle

20130406_pretty_right_trianglle_spec

describe 'print_triangle' do
  before(:each) do
    @output = StringIO.new
    @old_stdout = $stdout
    $stdout = @output
  end
 
  it "prints nothing if given 0" do
    print_triangle(0)
    @output.rewind
    @output.read.should be_empty
  end
 
  it "prints '*' if given 1" do
    print_triangle(1)
    @output.rewind
    @output.read.should eq "*\n"
  end
 
  it "prints a 5-row triangle" do
    print_triangle(5)
    @output.rewind
    @output.read.should eq "*\n**\n***\n****\n*****\n"
  end
 
  it "has the correct last line for a 100-row triangle" do
    print_triangle(100)
    @output.rewind
    @output.read.split("\n").last.should eq '*'*100
  end
 
  after(:each) do
    $stdout = @old_stdout
  end
end

20130406_Print out a pretty right triangle.rb

# print_triangle(rows) prints out a right triangle of +rows+ rows consisting 
# of * characters
#
# +rows+ is an integer
#
# For example, print_triangle(4) should print out the following: 
# *
# **
# ***
# ****

def print_triangle(rows)
  # Your code goes here!
end