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SUBROUTINE sla_DD2TF (NDP, DAYS, SIGN, IHMSF)
*+
* - - - - - -
* D D 2 T F
* - - - - - -
*
* Convert an interval in days into hours, minutes, seconds
* (double precision)
*
* Given:
* NDP i number of decimal places of seconds
* DAYS d interval in days
*
* Returned:
* SIGN c '+' or '-'
* IHMSF i(4) hours, minutes, seconds, fraction
*
* Notes:
*
* 1) NDP less than zero is interpreted as zero.
*
* 2) The largest useful value for NDP is determined by the size
* of DAYS, the format of DOUBLE PRECISION floating-point numbers
* on the target machine, and the risk of overflowing IHMSF(4).
* For example, on the VAX, for DAYS up to 1D0, the available
* floating-point precision corresponds roughly to NDP=12.
* However, the practical limit is NDP=9, set by the capacity of
* the 32-bit integer IHMSF(4).
*
* 3) The absolute value of DAYS may exceed 1D0. In cases where it
* does not, it is up to the caller to test for and handle the
* case where DAYS is very nearly 1D0 and rounds up to 24 hours,
* by testing for IHMSF(1)=24 and setting IHMSF(1-4) to zero.
*
* P.T.Wallace Starlink 19 March 1999
*
* Copyright (C) 1999 Rutherford Appleton Laboratory
*-
IMPLICIT NONE
INTEGER NDP
DOUBLE PRECISION DAYS
CHARACTER SIGN*(*)
INTEGER IHMSF(4)
* Days to seconds
DOUBLE PRECISION D2S
PARAMETER (D2S=86400D0)
INTEGER NRS,N
DOUBLE PRECISION RS,RM,RH,A,AH,AM,AS,AF
* Handle sign
IF (DAYS.GE.0D0) THEN
SIGN='+'
ELSE
SIGN='-'
END IF
* Field units in terms of least significant figure
NRS=1
DO N=1,NDP
NRS=NRS*10
END DO
RS=DBLE(NRS)
RM=RS*60D0
RH=RM*60D0
* Round interval and express in smallest units required
A=ANINT(RS*D2S*ABS(DAYS))
* Separate into fields
AH=AINT(A/RH)
A=A-AH*RH
AM=AINT(A/RM)
A=A-AM*RM
AS=AINT(A/RS)
AF=A-AS*RS
* Return results
IHMSF(1)=MAX(NINT(AH),0)
IHMSF(2)=MAX(MIN(NINT(AM),59),0)
IHMSF(3)=MAX(MIN(NINT(AS),59),0)
IHMSF(4)=MAX(NINT(MIN(AF,RS-1D0)),0)
END
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