Evalaute a string left to right

Given an input string that represents a function (like 'f(x) = x^2 +2/2x+3') and a input value (like x=2), how can I evaluate something of this form from left to right (ignoring the pemdas rules). I think I should use some loop for this

Answer 1

[James Tursa]

If you will accept evaluating this all at once, here is one way to do it (only works if the rhs is legit MATLAB syntax, which your example isn't):

>> s = 'f(x) = x^2 + 2/(2*x) + 3'
s =
f(x) = x^2 + 2/(2*x) + 3
>> e = find(s=='=',1)
e =
     6
>> p = find(s=='(',1)
p =
     2
>> f = str2func(['@' s(p:e-1) s(e+1:end)])
f = 
    @(x)x^2+2/(2*x)+3
>> f(2)
ans =
    7.5000

If you really need to evaluate it piecemeal for some reason, that is going to be much more involved because you will need to code up a parser with operator precedences etc.