subroutine ident( conj, add, epsilon, n, pp,    qq   )
integer i,        conj, add,          n
real 			     epsilon,    pp(n), qq(n)  # equivalence (pp,qq) OK
if( conj == 0 ) {
	if( add == 0 ) { do i=1,n {  qq(i) =         epsilon * pp(i) } }
	else           { do i=1,n {  qq(i) = qq(i) + epsilon * pp(i) } }
	}
else {  if( add == 0 ) { do i=1,n {  pp(i) =         epsilon * qq(i) } }
	else           { do i=1,n {  pp(i) = pp(i) + epsilon * qq(i) } }
	}
return; end