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.help dfltin Jun99 "Slalib Package"
.nf
SUBROUTINE slDFLI (STRING, NSTRT, DRESLT, JFLAG)
- - - - - - -
D F L I
- - - - - - -
Convert free-format input into double precision floating point
Given:
STRING c string containing number to be decoded
NSTRT i pointer to where decoding is to start
DRESLT d current value of result
Returned:
NSTRT i advanced to next number
DRESLT d result
JFLAG i status: -1 = -OK, 0 = +OK, 1 = null, 2 = error
Notes:
1 The reason DFLTIN 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 DFLTIN 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 D0.
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 DRESLT is left untouched.
12 NSTRT = 1 for the first character in the string.
13 On return from DFLTIN, 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 DFLTIN, 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,
DFLTIN does not detect that '1D999' 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 FLOTIN and INTIN
Called: slICHF
P.T.Wallace Starlink 18 March 1999
Copyright (C) 1999 Rutherford Appleton Laboratory
Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
.fi
.endhelp
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