Procedure

     BENUM  ( Be a number? )

     LOGICAL FUNCTION BENUM  ( STRING )

Abstract

     Determine whether a string represents a number.

Required_Reading

     None.

Keywords

     ALPHANUMERIC
     NUMBERS
     SCANNING
     UTILITY

Declarations

     IMPLICIT NONE

     CHARACTER*(*)         STRING

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     STRING     I   Character string.

     The function returns .TRUE. if the string is a number.
     Otherwise, it returns .FALSE.

Detailed_Input

     STRING   is any string.

Detailed_Output

     If the input string contains a number (as defined in
     $Particulars below) the function returns .TRUE. Otherwise,
     the function returns .FALSE.

Parameters

     None.

Exceptions

     Error free.

Files

     None.

Particulars

     A number may be either of the following:

        1) A decimal number (as defined by function BEDEC).

        2) A decimal number followed by an exponent character
           ('E', 'e', 'D', or 'd') and an integer (as defined
           by function BEINT).

Examples

     Four classes of numbers recognized by the various BE functions.

        UNS      unsigned integer
        INT      integer                (includes INT)
        DEC      decimal number         (includes UNS, INT)
        NUM      number                 (includes UNS, INT, NUM)

     The following table illustrates the differences between
     the classes. (Any number of leading and trailing blanks
     are acceptable.)

        String                  Accepted by
        ------------------      ------------------
        0                       UNS, INT, DEC, NUM
        21
        21994217453648

        +0                      INT, DEC, NUM
        -13
        +21946

        1.23                    DEC, NUM
        12.
        .17
        +4.1
        -.25

        2.3e17                  NUM
        17.D-13275849
        -.194265E+0004

     Note that the functions don't take the magnitudes of the numbers
     into account. They may accept numbers that cannot be represented
     in Fortran variables. (For example, '2.19E999999999999' probably
     exceeds the maximum floating point number on any machine, but
     is perfectly acceptable to BENUM.)

     The following strings are not accepted by any of the functions.

        String             Reason
        ---------------    ----------------------------------------
        3/4                No implied operations (rational numbers)
        37+14              No explicit operations
        E12                Must have mantissa
        217,346.91         No commas
        3.14 159 264       No embedded spaces
        PI                 No special numbers
        FIVE               No textual numbers
        CXIV               No roman numerals

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

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

Version

    SPICELIB Version 1.1.0, 24-NOV-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.0.0, 01-DEC-1995 (WLT)