complex<> using list initializer vs constructor?

Question

I'm reading Stroustrup C++ 4th Ed. Page 162 Types and Declarations. Specifically, where the following is allowed to construct a complex<> object.

The book comments that case A is "use constructor". Is case A really a list initializer and the constructor method of initialization is performed in B or C?

#include <iostream>
#include <complex>
using namespace std;

int main(int argc, char *argv[])
{
    complex<double> z = { 0, 3.14 }; // A
    complex<double> h(0, 3.14); // B
    complex<double> i{0, 3.14}; // C

    return 0;
}

All three cases are initialised using the same constructor. B does direct initialisation. Since C++11, cases A and C do aggregate initialisation (or, more specifically, copy list initialisation and direct list initialisation, respectively). — Peter, Jun 03 '20 at 04:13
Is one better than the other? All these ways of initializing an object is becoming confusing :( — notaorb, Jun 03 '20 at 20:25
@notaorb There're subtle differences among them, even not in this case. See [Why is list initialization (using curly braces) better than the alternatives?](https://stackoverflow.com/q/18222926/3309790) — songyuanyao, Jun 04 '20 at 09:38

songyuanyao · Accepted Answer · 2020-06-05T01:03:33.533

0

complex<double> z = { 0, 3.14 }; // A performs copy-list-initliazation (since C++11).
complex<double> h(0, 3.14); // B performs direct initliazation.
complex<double> i{0, 3.14}; // C performs direct-list-initliazation (since C++11).

The effects are all the same for this case; objects are initialized by the constructor complex::complex(double, double).

edited Jun 05 '20 at 01:03

answered Jun 03 '20 at 04:04

songyuanyao

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complex<> using list initializer vs constructor?

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