Working with inputs in functions

I have got a problem. I need to code a bisection program in Matlab but I need to make it useful for any mathematical function the user wants. Does anyone know how to write a code without defining the mathematical function (leaving the option for the user) on which the program will work on?

[Stephen23]

That is what function handles are for! Either get the user to:

• define a function handle, or
• define a string (in MATLAB syntax) and convert this using str2func.

[Renan Portela]

how should i code in order to make it possible? how should I code to allow the user type in the function ? So far I wrote this code below but it works just for one single function which is written below.

clc
fprintf('  itteration     a        b        lambda    mi      f(lamda)  f(mi)    \n')
clear 
f=@(x) x^2 + 2*x;
format short
eps_abs = 1e-1;
eps_step = 1e-1;
a = -3;
b = 5.0;
iter=0;
max = 15;
datasave=[];