SLASRT2 - the numbers in D in increasing order (if ID = 'I') or in decreasing
order (if ID = 'D' )

- SUBROUTINE SLASRT2(
- ID, N, D, KEY, INFO )

CHARACTER ID INTEGER INFO, N INTEGER KEY( * ) REAL D( * )

Sort the numbers in D in increasing order (if ID = 'I') or in decreasing order
(if ID = 'D' ). Use Quick Sort, reverting to Insertion sort on arrays of

size <= 20. Dimension of STACK limits N to about 2**32.

- ID (input) CHARACTER*1
- = 'I': sort D in increasing order;

= 'D': sort D in decreasing order.

- N (input) INTEGER
- The length of the array D.

- D (input/output) REAL array, dimension (N)
- On entry, the array to be sorted. On exit, D has been sorted into
increasing order (D(1) <= ... <= D(N) ) or into decreasing order
(D(1) >= ... >= D(N) ), depending on ID.

- KEY (input/output) INTEGER array, dimension (N)
- On entry, KEY contains a key to each of the entries in D() Typically,
KEY(I) = I for all I On exit, KEY is permuted in exactly the same manner
as D() was permuted from input to output Therefore, if KEY(I) = I for all
I upon input, then D_out(I) = D_in(KEY(I))

- INFO (output) INTEGER
- = 0: successful exit

< 0: if INFO = -i, the i-th argument had an illegal value