Prefer initialization to assignment in constructors

Reason

An initialization explicitly states that initialization, rather than assignment, is done and can be more elegant and efficient. Prevents "use before set" errors.

Example, good

class A {   // Good
    string s1;
public:
    A(czstring p) : s1{p} { }    // GOOD: directly construct (and the C-string is explicitly named)
    // ...
};

Example, bad

class B {   // BAD
    string s1;
public:
    B(const char* p) { s1 = p; }   // BAD: default constructor followed by assignment
    // ...
};

class C {   // UGLY, aka very bad
    int* p;
public:
    C() { cout << *p; p = new int{10}; }   // accidental use before initialized
    // ...
};

Example, better still

Instead of those const char*s we could use C++17 std::string_view or gsl::span<char> as a more general way to present arguments to a function:

class D {   // Good
    string s1;
public:
    D(string_view v) : s1{v} { }    // GOOD: directly construct
    // ...
};