CODEWITHSUNDEEP
c++c++11
vladkkkkk
vladkkkkk

Reputation: 276

Reduce number of arguments

Suppose I have a method:

std::vector<double> minimize(double (*f)(const std::vector<double>& x))

that takes a function f(x) and finds x that minimizes it. Suppose I want to minimize a function g(x, a) (with respect to x) which also takes a parameter a as an argument:

double g(const std::vector<double>& x, const double a)

How can I do this (in c++11) using the method minimize if the value of a is known only at runtime?

Upvotes: 0

Views: 883

Answers (2)

Pavlo Mur
Pavlo Mur

Reputation: 347

Use labda as Puppy suggested, but additinally update minimize to be a function template. Using template parameter instead of std::function will dramatically speed up minimize

//somewhere in header file
template<class Function>
std::vector<double> minimize(const Function& f){
    ... 
}
...
//in any place where minimize is visible
minimize([=](const std::vector<double>& x) { return g(x, a); });

Upvotes: 1

Puppy
Puppy

Reputation: 146930

You can easily use a lambda.

minimize([=](const std::vector<double>& x) { return g(x, a); });

This is assuming that you change your function to use std::function instead of a function pointer. Function pointers are terribly limited and can't do anything interesting at all, like this, so it's best to forget they exist.

Upvotes: 4

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