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lstltd_c

 Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input Detailed_Output Parameters Exceptions Files Particulars Examples Restrictions Literature_References Author_and_Institution Version Index_Entries

Procedure

lstltd_c ( Last double precision element less than )

SpiceInt lstltd_c ( SpiceDouble         x,
SpiceInt            n,
ConstSpiceDouble  * array )

Abstract

Find the index of the largest array element less than
a given number `x' in an array of non-decreasing numbers.

None.

ARRAY
SEARCH

Brief_I/O

VARIABLE  I/O  DESCRIPTION
--------  ---  --------------------------------------------------
x          I   Upper bound value to search against.
n          I   Number of elements in `array'.
array      I   Array of possible lower bounds.

The function returns the index of the last element of `array' that
is less than `x'.

Detailed_Input

x           is a double precision value acting as an upper bound: the
element of `array' that is the greatest element less than `x'
is to be found.

n           is the total number of elements in `array'.

array       is an array of double precision numbers that forms a
non-decreasing sequence. The elements of array need not
be distinct.

Detailed_Output

The function returns the index of the highest-indexed element in
the input array that is less than `x'. The routine assumes the array
elements are sorted in non-decreasing order.

Indices range from 0 to n-1.

If all elements of `array' are greater than or equal to `x', the
routine returns the value -1. If `n' is less than or equal to zero,
the routine returns the value -1.

None.

Exceptions

Error free.

1)  If `n' is less than or equal to zero, the function returns -1.
This case is not treated as an error.

2)  If the input array is not sorted in non-decreasing order, the
output of this routine is undefined. No error is signaled.

None.

Particulars

This routine uses a binary search algorithm and so requires
at most on the order of

log (n)
2

steps to compute the value of lstltd_c.

Note: If you need to find the first element of the array that is
greater than or equal to `x', simply add 1 to the result returned by
this function and check to see if the result is within the array
bounds given by `n'.

Examples

1)  Let array be assigned the following values:

array = -2.0;
array = -2.0;
array =  0.0;
array =  1.0;
array =  1.0;
array = 11.0;

The table below demonstrates the behavior of lstltd_c:

Call                       Returned Value
===========================          ==============
lstltd_c ( -3.0, 6, array )                -1

lstltd_c ( -2.0, 6, array )                -1

lstltd_c (  0.0, 6, array )                 1

lstltd_c (  1.0, 6, array )                 2

lstltd_c ( 11.1, 6, array )                 5

Restrictions

1)  If the sequence of double precision numbers in the input array
`array' is not non-decreasing, the program will run to
completion but the index found will not mean anything.

None.

Author_and_Institution

N.J. Bachman        (JPL)
J. Diaz del Rio     (ODC Space)
W.L. Taber          (JPL)

Version

-CSPICE Version 1.0.1, 01-NOV-2021 (JDR)

Edited the header to comply with NAIF standard. Improved
-Detailed_Input, -Detailed_Output, -Particulars, -Exceptions and
-Restrictions sections.

-CSPICE Version 1.0.0, 10-JUL-2002 (NJB) (WLT)

Index_Entries

last d.p. element less_than
Fri Dec 31 18:41:09 2021