Function name as argument but with different number of argument

Question

I have written a bisection solver with a function name as argument and that function has only one argument:

double Bisection(double(*func)(double), double xLower, double xUpper, double xEPS = 1e-9, double yEPS = 1e-9);

Now I want to apply this solver in a Beta inverse cumulative probability function where the CDF is already known. But this CDF has three argument where the last two arguments are known:

double CDF(double x, double alpha, double beta)

How should I use this CDF as an argument of the solver by reducing the number of arguments?

John Zwinck · Accepted Answer · 2017-08-26 02:40:18Z

1

The first step is to replace your C-style function pointer with a C++ std::function:

double Bisection(std::function<double(double)> func, double xLower, double xUpper, double xEPS = 1e-9, double yEPS = 1e-9);

The implementation will be the same as before. Now you can use std::bind() to call it:

double alpha, beta, xLower, xUpper; // TODO: assign
Bisection(std::bind(CDF, _1, alpha, beta), xLower, xUpper);

What std::bind() does there is to convert your three-argument CDF function into a one-argument (_1) function by binding the second and third arguments to variables.

You can't use std::bind() with your original C-style function pointer, as discussed here: convert std::bind to function pointer

answered Aug 26, 2017 at 2:40

John Zwinck

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1 Comment

Yang Wang Over a year ago

This is really a great solution!

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