c++ - Very simple optimization algorithm producing a function parameter error -

i trying write program maximizes function, f(x). algorithm is:

double maxx(double(*f)(const double &), double &a, double &b, const double tol = 1e-5) {     static double goldenratio = 0.618034;     double c = b - goldenratio * (b - a);     double d = + goldenratio * (b - a);     while (abs(c - d) > tol)     {         double fc = (*f)(c); double fd = (*f)(d);         if (fc > fd)         {             b = d;             d = c;             c = b - goldenratio * (b - a);         }         else         {             = c;             c = d;             d = + goldenratio * (b - a);         }     }     return 0.5 * (b + a); } 

i getting error when call function in main(). error message is:

severity code description project file line error c2572 'maxx': redefinition of default argument: parameter 1

what doing wrong here? put full code here: https://cloudup.com/cqhb_dkdiaf

you're declaring default argument value in function declaration ("prototype") on line 32, and in definition on line 53. reasons unknown me, gods of c++ have decided not allowed: see following excerpt 8.3.6/4 of c++ 2003 standard:

a default argument shall not redefined later declaration (not same value).

note quite old c++ 03 standard -- either compiler you're using still in mode, or behaviour remains unchanged in c++11, or both.

[edit] forgot mention how solve problem! delete default argument every declaration except first.