Track the presence of variables and their number of occurrences in a parsed expression
@param counter a zero-initialized array where the count of each variable will be stored
@param size size of array
@return 0 on success, a negative value indicates that no expression or array was passed
or size was zero
Track the presence of variables and their number of occurrences in a parsed expression
@param counter a zero-initialized array where the count of each variable will be stored @param size size of array @return 0 on success, a negative value indicates that no expression or array was passed or size was zero