- check if a derivative transfer function pointer is valid
SYNOPSIS
int valid_der_transfer_function
(ptr)
ARGUMENTS
void
*ptr
A pointer to a derivative transfer function.
RETURNS
TRUE if the derivative transfer function exists, FALSE if not.
FUNCTION
This routine searches the function with address ptr. A list of these functions is
stored in DerTransFuncs (see FUNCTION-variables). The function
is used by valid_trans_func.