SLA_AFIN - Sexagesimal character string to angle   

ACTION:

Decode a free-format sexagesimal string (degrees, arcminutes, arcseconds) into a single precision floating point number (radians).

CALL:

CALL sla_AFIN (STRING, NSTRT, RESLT, JF)

GIVEN:

STRING string containing deg, arcmin, arcsec fields

NSTRT I pointer to start of decode (beginning of STRING = 1)

RETURNED:

NSTRT advanced past the decoded angle

RESLT R angle in radians

JF I status: 0 = OK +1 = default, RESLT unchanged (note 2) -1 = bad degrees (note 3) -2 = bad arcminutes (note 3) -3 = bad arcseconds (note 3)

EXAMPLE:

argument	before	after
STRING	'-57 17 44.806 12 34 56.7'	unchanged
NSTRT	1	16 (i.e. pointing to 12...)
RESLT	-	-1.00000
JF	-

A further call to sla_AFIN, without adjustment of NSTRT, will decode the second angle, $12^{\circ}\,34^{'}\,56^{''}.7$.

NOTES:

1.

The first three ``fields'' in STRING are degrees, arcminutes, arcseconds, separated by spaces or commas. The degrees field may be signed, but not the others. The decoding is carried out by the sla_DFLTIN routine and is free-format.

2.

Successive fields may be absent, defaulting to zero. For zero status, the only combinations allowed are degrees alone, degrees and arcminutes, and all three fields present. If all three fields are omitted, a status of +1 is returned and RESLT is unchanged. In all other cases RESLT is changed.

3.

Range checking:

• The degrees field is not range checked. However, it is expected to be integral unless the other two fields are absent.
• The arcminutes field is expected to be 0-59, and integral if the arcseconds field is present. If the arcseconds field is absent, the arcminutes is expected to be 0-59.9999...
• The arcseconds field is expected to be 0-59.9999...
• Decoding continues even when a check has failed. Under these circumstances the field takes the supplied value, defaulting to zero, and the result RESLT is computed and returned.

4.

Further fields after the three expected ones are not treated as an error. The pointer NSTRT is left in the correct state for further decoding with the present routine or with sla_DFLTIN etc. See the example, above.

5.

If STRING contains hours, minutes, seconds instead of degrees etc, or if the required units are turns (or days) instead of radians, the result RESLT should be multiplied as follows:

for STRING	to obtain	multiply RESLT by
${\circ}$  '  ''	radians	1.0
${\circ}$  '  ''	turns	$1/{2 \pi} = 0.1591549430918953358$
h m s	radians	15.0
h m s	days	$15/{2\pi} = 2.3873241463784300365$