20.8 Variables used before assignment

A warning is generated when any variable is used before it has been assigned a value.

For example, consider the following program.

transformed data {
  real x;
  if (1 > 2)
    x = 1;
  else
    print("oops");
  print(x);
}

Since x is only assigned in one of the branches of the if statement, it might get to print(x) without having been assigned to.

Pedantic mode produces the following warning.

Warning at 'uninit-warn.stan', line 7, column 8 to column 9:
  The variable x may not have been assigned a value before its use.