I have to write a function that receives std::vector<int> as the first argument, and a vector of functions that will be applied over each element in the vector. If the element does not meet the criteria of all predicate functions, in that case I have to replace that element with the default third argument that the function receives, which has a value of -1. If any predicate function returns false, that element should be replaced with the default argument.
This is what I've written so far:
#include <iostream>
#include <vector>
#include <functional>
typedef std::vector<std::function<bool(int)>> Functions;
void default_if_not_all(std::vector<int>& i, Functions f,int def=-1){
for(auto& num : i){
for(auto& fun : f){
if(!(fun(num))){
num=def;
}
}
}
}
int main(){
std::vector<int> v{1,2,3,4,5};
Functions f{
[&](int a){if( a>0 )return 1;},
[&](int a){if (a%2==0) return 1;}
};
for(const auto& e : v){
std::cout<<e<<" ";
}
std::cout<<std::endl;
}
The problem is that I am not sure how to call the functions from the vector of functions in the right way so that I can change the value of the elements in the int vector.
Does anyone have some advice how to use typedef Functions properly in this case? Am I on the right track?
Your lambda functions only return a value in the true case. You need to return false too.
You don't need if for that. Just return the result of the comparison:
// note: the lambda capture isn't really needed since it's not used
Functions f{[&](int a) { return a > 0; },
[&](int a) { return a % 2 == 0; }};
You also need to call your default_if_not_all afterwards:
default_if_not_all(v, f);