Solving a simple integral with input equation from user

I am using this code to enter an equation and solve a simple integral

str = input('Enter an equation in x: ','s') ;
f = function_handle.empty; 
f = eval(['@()', str]);
x = f(); 
xmin= input('Lower limit of x: ')
xmax= input('Upper limit of x: ')
int(x, xmin, xmax)

But I get this error

Undefined function 'int' for input arguments of type 'double'.

Error in Untitled5 (line 7)
int(x,xmin, xmax)

Answer 1

[Rafael Hernandez-Walls]

syms x
str = input('Enter an equation in x: ','s') ;
f = function_handle.empty; 
f = eval(['@(x)', str]);
%x = f(); 
xmin= input('Lower limit of x: ')
xmax= input('Upper limit of x: ')
int(f,x, xmin, xmax)

[Walter Roberson]

Using eval() is not recommended, and is not necessary. If you were going to generate an anonymous function from a character vector, then use str2func() . But considering that that symbolic integration int() is being used, it does not make sense to convert to an anonymous function: it makes more sense to convert to a symbolic expression or possibly symbolic function.

Answer 2

[Walter Roberson]

syms x
str = input('Enter an equation in x: ','s') ;
f = str2sym(str) ;
xmin= input('Lower limit of x: ')
xmax= input('Upper limit of x: ')
int(f,x, xmin, xmax)