lib/dydx/integrand.rb in dydx-0.1.4 vs lib/dydx/integrand.rb in dydx-0.1.25

@@ -1,38 +1,26 @@
 module Dydx
   class Integrand
     attr_accessor :function, :var
-
     def initialize(function, var)
       @function = function
       @var = var
     end
 
-    def [](a, b, n = 1000)
+    def [](a, b, n = 100)
+      f = function
+      a, b = [a, b].map(&:to_f)
+      raise ArgumentError, 'b should be greater than a' if a > b
       # HOT FIX: should implement Infinity class
       a = - 1000 if a == - Float::INFINITY
       b = 1000 if b == Float::INFINITY
 
-      a, b = [a, b].map(&:to_f)
-      fail ArgumentError, 'b should be greater than a' if a > b
-      $temp_cal_f = function
-
-      n = [n, (b - a) * 2].max
-      n += 1 if n.to_i.odd?
       h = (b - a) / n
-      x = ->(i) { a + h * i }
-
-      odd_sum = (1..n - 1).to_a.select(&:odd?).inject(0) { |sum, i| sum += f(x.(i)) }
-      even_sum = (1..n - 1).to_a.select(&:even?).inject(0) { |sum, i| sum += f(x.(i)) }
-      round_8( (h / 3) * (f(a) + f(b) + 2 * even_sum + 4 * odd_sum) )
-    end
-
-    def f(vars)
-      temp_cal_f(vars)
-    end
-
-    def round_8(num)
-      return num if num.abs == Float::INFINITY
-      (num * 10 ** 8).round * 10.0 ** (-8)
+      sum = 0.0
+      xi = ->(i){ a + h * i }
+      n.to_i.times do |i|
+        sum += ( f(xi.(i)) + 4.0 * f(xi.(i) + h / 2.0 ) + f(xi.(i) + h) )
+      end
+      ( h * sum ) / 6.0
     end
   end
 end