Integral Calculator wont work when given formula given more than 1 x in the formula

Question

So I'm working on an integral calculator right now, and it works fairly well, although as soon as defining y as x**2+x*2+2 it stops working. What prompts my program to work with y = x**2+2 but not with y = x**2+x*2+2?

import math as math

x0 = 0                                                                                      
x1 = 0                                                                                      

def func(y, x):                                                                             
    return eval(y)

def func2(z, x):                                                                            
    return eval(z)

def func3(c, d):        
    a = 0.0                                                                                 
    for i in range(1, n+1):                                                                 
        x0 = a + (i-1) * dx                                                                     
        Ai = dx * (c + d)/ 2.                                                           
        a = a + Ai                                                                      
    return a

y = str(raw_input("Function 1: "))                                                      
z = str(raw_input("Function 2: "))                                          

a = float(input("Left boundary: "))                                                     
b = float(input("Right boundary: "))                                                    
dx = float(input("Trapezoid width: "))                                                      

n = int((b - a) / dx)                                                               

Area2 = func3(func(y, x0), func(y, x1))                                                                             
Area3 = func3(func2(z, x0), func2(z, x1))

Area4 = Area2 - Area3
if Area4 < 0:
    Area4 = Area3 - Area2

print "Area = ", Area4

In what sense is it unclear? I am asking for someone to figure out why it will give me the correct result for y=x\**2+2 z=x\**2 but not for y=x\**2+2x+2 z=x\**2 — Meh, Apr 07 '17 at 14:47
Note that `func` and `func2` are identical and neither does anything with the second parameter. — tobias_k, Apr 07 '17 at 14:53
@tobias_k yes, i know. changing that does nothing to fix my problem though — Meh, Apr 07 '17 at 15:05
Please explain just what you mean by "it stops working". See [How to create a Minimal, Complete, and Verifiable example](http://stackoverflow.com/help/mcve). — Rory Daulton, Apr 07 '17 at 16:31

score 0 · Accepted Answer · answered Apr 07 '17 at 15:58

import math as math

x0 = 0                                                                                      
x1 = 0                                                                

def f(function, x):
   function = eval(function)
   return function

def func3(b, a, func):        
   area = 0.0
   dx = (b - a) / n                                                
   for i in range(1, n+1):                                                                 
       x0 = a + (i-1) * dx  
       x1 = a + i*dx
       Ai = dx * (f(func, x0) + f(func, x1))/ 2.                                                          
       area = area + Ai                                                                      
   return area

y = str(input("Function 1: "))                                                      
z = str(input("Function 2: "))                                          

a = float(input("Left boundary: "))                                                     
b = float(input("Right boundary: "))                                                    
n = int(input("Trapezoid width: "))                                                      


Area2 = func3(b, a, y)                                                                             
Area3 = func3(b, a, z)

Area4 = Area2 - Area3
if Area4 < 0:
   Area4 = Area3 - Area2

print "Area = ", Area4

Is this more or less what you wanted to do?

Integral Calculator wont work when given formula given more than 1 x in the formula

1 Answers1