pub fn dpstrf(
ctx: &mut SpiceContext<'_>,
x: f64,
sigdig: i32,
format: char,
string: &mut str,
)Expand description
Double Precision Number to Character
Take a double precision number and convert it to an equivalent formatted character string representation (base 10).
§Brief I/O
VARIABLE I/O DESCRIPTION
-------- --- --------------------------------------------------
X I A double precision number
SIGDIG I The number of significant digits saved for output
FORMAT I 'E' for scientific, 'F' for floating point.
STRING O A character string representation of X§Detailed Input
X is a double precision number.
SIGDIG is the number of significant digits that are desired
for the output string.
FORMAT is a character flag that indicates how the double
precision number should be represented. The two
acceptable inputs are 'E' and 'F'. If the input
is 'E' then the number will be displayed with an
exponent in scientific notation. It will have the
form 'sx.xxx - - - xxxxxEsyy' where there are
SIGDIG x's and s is ' ' or '-' at its first occurrence
and '-' or '+' in the second.
If the input is 'F' then the number will be
displayed without an exponent --- the representation
will be strictly decimal. The first symbol will be
a sign ('-' or ' ').§Detailed Output
STRING is a character representation of X to the number of
significant digits specified by SIGDIG. The number of
spaces required to return the requested character
string is SIGDIG + 6. If STRING is not declared to
have adequate length, the number returned will be
truncated on the right.§Exceptions
Error free.
1) If SIGDIG is less than one, this routine returns one
significant digit in the output string.§Particulars
This routine computes an approximate character representation
of the input string X. The maximum number of significant
digits returned is 14 (in F format there may be many extra
zeros returned but only a maximum of 14 digits will be
significant.
The output string is left justified.
This routine has the advantage that it does not use an internal
file and is about twice as fast as an internal write. It can
be used as part of character function without fear of introducing
recursive I/O conflicts. It is intended to be an approximate
inverse to the subroutine NPARSD.
IF you want the character string representation of a double
precision number to be the same as that produced by a formatted
write statement use a FORTRAN write statement.
For example the number represented by the string
1.245454545454545454545E+01
when read (via a FORTRAN READ statement) into the DP variable X
and converted back to a character string having 14 significant
digits by this routine yields
1.2454545454545E+01 in E format
12.454545454545 in F format
The FORTRAN write statement
WRITE ( 6, FMT='(P1E)' ) X
yields
1.2454545454545454E+01
If this is too much error for your application DO NOT use this
routine. You should be aware however, that a character string
read into a double precision number may not WRITE out with an
equivalent character representation as was input.
For example on a VAX 11/780 if you
READ (5,*) X
WRITE (6,FMT='(E)') X
and enter a value of 7.00000001 for the read statement
the output written will be 0.7000000010000001E+01§Examples
Suppose that you wished to insert the character representation
of some DOUBLE PRECISION number into a line of text.
For example suppose X contains the double precision number
4.268176872928187 and you would like to insert the character
representation of this number to 2 places between the strings
'There are', 'meters between lamp posts'
You could perform the following sequence of steps
DOUBLE PRECISION X
CHARACTER*5 DISTANCE
CHARACTER*80 MESSAGE
CALL DPSTRF ( X, 2, 'F', DISTANCE )
MESSAGE = 'There are ' //
. DISTANCE //
. 'meters between lamp posts'
.
C
C Squeeze any extra spaces out of the message string.
C
CALL CMPRSS ( ' ', 1, MESSAGE, MESSAGE )
The string MESSAGE would contain:
'There are 4.2 meters between lamp posts'§Restrictions
1) The maximum number of significant digits returned is 14.
2) If the output string is not declared to be adequately large
the numeric string will be truncated to the side opposite its
justification (At least SIGDIG + 6 characters are needed in E
format, in F format the size required is dependent upon the
input X and the number of significant digits requested. In
extreme cases up to 56 characters may be required.)
3) This routine makes explicit use of the format of the string
returned by DPSTR, should that routine change, substantial
work may be required to bring this routine back up to snuff.§Author and Institution
J. Diaz del Rio (ODC Space)
W.L. Taber (JPL)§Version
- SPICELIB Version 1.2.1, 12-AUG-2021 (JDR)
Edited the header to comply with NAIF standard.
- SPICELIB Version 1.2.0, 17-SEP-1996 (WLT)
Upgraded routine to handle arbitrary magnitude d.p. numbers.
- SPICELIB Version 1.1.1, 10-MAR-1992 (WLT)
Comment section for permuted index source lines was added
following the header.
- SPICELIB Version 1.1.0, 30-JUL-1990 (WLT)
The routine was repaired so that references to zero-length
strings ( for example STRING(4:3) ) are not made.
- SPICELIB Version 1.0.0, 31-JAN-1990 (WLT)§Revisions
- SPICELIB Version 1.1.0, 30-JUL-1990 (WLT)
As previously implemented, one would occasionally reference
a zero length substring of the variable NUMSTR. This was
O.K. under VAX Fortran, because it allows such references.
However, most implementations of Fortran are not as forgiving.