.help flotin Jun99 "Slalib Package"
.nf

      SUBROUTINE slRFLI (STRING, NSTRT, RESLT, JFLAG)

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      R F L I
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  Convert free-format input into single precision floating point

  Given:
     STRING     c     string containing number to be decoded
     NSTRT      i     pointer to where decoding is to start
     RESLT      r     current value of result

  Returned:
     NSTRT      i      advanced to next number
     RESLT      r      result
     JFLAG      i      status: -1 = -OK, 0 = +OK, 1 = null, 2 = error

  Called:  slDFLI

  Notes:

     1     The reason FLOTIN has separate OK status values for +
           and - is to enable minus zero to be detected.   This is
           of crucial importance when decoding mixed-radix numbers.
           For example, an angle expressed as deg, arcmin, arcsec
           may have a leading minus sign but a zero degrees field.

     2     A TAB is interpreted as a space, and lowercase characters
           are interpreted as uppercase.

     3     The basic format is the sequence of fields #^.^@#^, where
           # is a sign character + or -, ^ means a string of decimal
           digits, and @, which indicates an exponent, means D or E.
           Various combinations of these fields can be omitted, and
           embedded blanks are permissible in certain places.

     4     Spaces:

             .  Leading spaces are ignored.

             .  Embedded spaces are allowed only after +, -, D or E,
                and after the decomal point if the first sequence of
                digits is absent.

             .  Trailing spaces are ignored;  the first signifies
                end of decoding and subsequent ones are skipped.

     5     Delimiters:

             .  Any character other than +,-,0-9,.,D,E or space may be
                used to signal the end of the number and terminate
                decoding.

             .  Comma is recognized by FLOTIN as a special case;  it
                is skipped, leaving the pointer on the next character.
                See 13, below.

     6     Both signs are optional.  The default is +.

     7     The mantissa ^.^ defaults to 1.

     8     The exponent @#^ defaults to E0.

     9     The strings of decimal digits may be of any length.

     10    The decimal point is optional for whole numbers.

     11    A "null result" occurs when the string of characters being
           decoded does not begin with +,-,0-9,.,D or E, or consists
           entirely of spaces.  When this condition is detected, JFLAG
           is set to 1 and RESLT is left untouched.

     12    NSTRT = 1 for the first character in the string.

     13    On return from FLOTIN, NSTRT is set ready for the next
           decode - following trailing blanks and any comma.  If a
           delimiter other than comma is being used, NSTRT must be
           incremented before the next call to FLOTIN, otherwise
           all subsequent calls will return a null result.

     14    Errors (JFLAG=2) occur when:

             .  a +, -, D or E is left unsatisfied;  or

             .  the decimal point is present without at least
                one decimal digit before or after it;  or

             .  an exponent more than 100 has been presented.

     15    When an error has been detected, NSTRT is left
           pointing to the character following the last
           one used before the error came to light.  This
           may be after the point at which a more sophisticated
           program could have detected the error.  For example,
           FLOTIN does not detect that '1E999' is unacceptable
           (on a computer where this is so) until the entire number
           has been decoded.

     16    Certain highly unlikely combinations of mantissa &
           exponent can cause arithmetic faults during the
           decode, in some cases despite the fact that they
           together could be construed as a valid number.

     17    Decoding is left to right, one pass.

     18    See also DFLTIN and INTIN

  P.T.Wallace   Starlink   23 November 1995

  Copyright (C) 1995 Rutherford Appleton Laboratory
  Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.

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