JuniorTheoryCommon

Which line does not compile?

C++

#include <iostream>

int main() {
    int a = 2.9;
    int b(2.9);
    double c{2};
    int d{2.9};
    std::cout << a << b << c << d << '\n';
}

int d{2.9};: braces refuse to drop the fraction of 2.9

Expecting = to refuse narrowing: int a = 2.9; compiles and drops the fraction, so a is 2; only braces make narrowing an error.
Expecting parentheses to work like braces: int b(2.9); converts the value as = does and compiles; only {} checks for narrowing.

Why does double c{2}; compile, while the clang compiler rejects int n = 2; double r{n};?
How would you rewrite int d{2.9}; so that it compiles when the fraction should be dropped?

JuniorTheoryCommon

C++

#include <iostream>

int main() {
    int a = 2.9;
    int b(2.9);
    double c{2};
    int d{2.9};
    std::cout << a << b << c << d << '\n';
}

int d{2.9};: braces refuse to drop the fraction of 2.9

Expecting = to refuse narrowing: int a = 2.9; compiles and drops the fraction, so a is 2; only braces make narrowing an error.
Expecting parentheses to work like braces: int b(2.9); converts the value as = does and compiles; only {} checks for narrowing.

Why does double c{2}; compile, while the clang compiler rejects int n = 2; double r{n};?
How would you rewrite int d{2.9}; so that it compiles when the fraction should be dropped?