Simple Integral implementation in Ruby

integrate.rb

require 'bigdecimal'

def integrate (a, b, n)
  a = a.to_f; b = b.to_f; n = n.to_i
  result = 0.0
  
  dx = (b - a) / n
  dx_half = dx / 2
  for i in 0 ... n
    result += yield a + (i * dx)
  end
  result * dx
end

def integrate_trapezoid (a, b, n)
  a = a.to_f; b = b.to_f; n = n.to_i
  result = 0.0
  
  result += ( yield(a) + yield(b) ) / 2
  
  dx = (b - a) / n
  
  for i in 1 ... n
    result += yield a + (i * dx)
  end
  result * dx
end


for n in 1..7

  a = -5
  b = 5

  before = Time.now
  
  integral = integrate(a,b,10 ** n) do |i|
    Math.sin i
  end
  
  time_taken = 1000.0 * (Time.now - before) 
  before = Time.now
 
  integral_trapezoid = integrate_trapezoid(a,b,10 ** n) do |i|
    Math.sin i
  end
  
  time_taken_trapezoid = 1000.0 * (Time.now - before) 
  
  puts "n=10^" + n.to_s + " | " + integral.to_s + " (" + time_taken.to_s + "ms)"
  puts "         " + integral_trapezoid.to_s + " (" + time_taken_trapezoid.to_s + "ms)"
  
end