Do invalid statements provide valid results [duplicate]

Question

I made this code and it should be invalid

#include<iostream>
using namespace std;

int main()
{
  int a,b;
  a=3,014;    //invalid
  b=(3,014);  //invalid
  cout<<a<<endl<<b;
}

Output:

3
12

However both the invalid statements give valid results. But the result should be 3014. It is changed. Why does this happen?

Answer 1

There's nothing "invalid" about either of those.

a = 3,014;

This parenthesizes as

(a = 3) , 014;

So a gets assigned the value 3, and then 014 (a number) gets evaluated and discarded. Hence, a = 3.

b = (3 , 014);

Here, we've explicitly put in parentheses. So the right-hand side is an application of the comma operator. The 3 gets evaluated then discarded. The 014 is an octal number, and 14 in base 8 is equal to 12 in base 10, so b = 12.