What is narrowing conversion

Narrowing conversion is a conversion of a value including the loss of it's precision. Most of the times that is not what you want. ^[1]

Below shows the level of narrowing conversion of data lossness.

long double > double > float > long > int > short > char

double d = 7.9;
int i = d; // bad, narrowing i becomes 7
i = (int) d; // bad, not explicit enough

void f(int x, long y, double d) {
	char c1 = x; // bad, narrowing
	char c2 = y; // bad, narrowing
	char c3 = z; // bad, narrowing
}

How to Avoid Narrowing Conversion

Since C++11, uniform initialization prohibits narrowing conversion by using braces. For example:

double x, y, z;
int sum1 = x + y + z; // Causion ! Narrowing conversion by assignment
int sum1{x+y+z}; // Compile will show error ! uniform initialization don't allow narrowing conversion.