Commas in for loop

Question

Why is the following line producing errors?

for(int i = 0, int pos = 0, int next_pos = 0; i < 3; i++, pos = next_pos + 1) {
  // …
}

error: expected unqualified-id before ‘int’
error: ‘pos’ was not declared in this scope
error: ‘next_pos’ was not declared in this scope

Compiler is g++.

Answer 1

You can have only one type of declaration per statement, so you only need one int:

for(int i = 0, pos = 0, next_pos = 0; i < 3; i++, pos = next_pos + 1)

Answer 2

In a normal program:

int main()
{

int a=0,int b=0,int c=0;
return 0;    

}

will never work and is not accepted.

This is what you are actually trying to do inside the for loop!