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

          ID is CHARACTER*1


          = 'I': sort D in increasing order;


          = 'D': sort D in decreasing order.

N

          N is INTEGER


          The length of the array D.

D

          D is 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.

INFO

          INFO is INTEGER


          = 0:  successful exit


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

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June 2016