Question

#include <iostream>

std::string getMyName(void)
{
  std:: cout << "This is function getMyName" << std::endl;
  return std::string("hello world");
}

std::string getMyName2(void)
{
  std:: cout << "This is function getMyName2" << std::endl;
  return std::string("hello world2");
}

int main(void)
{
  // what is the official name for the following syntax?
  bool isDone = (getMyName(), getMyName2(), false);

  std:: cout << "isDone " << isDone << std::endl;
  return 0;
}

user@ubuntu:~/Documents/C++$ ./period 
This is function getMyName
This is function getMyName2
isDone 0

As you can see the following statement is evaluated from left to right and the value of isDone is assigned with the last expression of value false.

bool isDone = (getMyName(), getMyName2(), false);

I would like to know the official syntax name for this statement. I have searched ‘period statement’ through G and without meaningful hits.

Thank you

Answer 1

You are making use of the comma operator

• http://en.wikipedia.org/wiki/Comma_operator

This operator will evaluate the left expression first, then evaluate the second and use it’s result as the result of the expression. It’s roughly equivalent to

getMyName();
getMyName2();
bool isDone = false;