Björn wrote:
> c) I am curious of what this number 1r10800p1 is all about.
That's conversion to arc minutes in radians, I think. An arc minute is 1%60
of a degree or (1%60) * pi%180 radians. The notation 1r10800p1 is just a
shorthand (atomic, single-word) way of expressing (1%60) * pi%180 .
Briefly:
(1%60) * pi%180
pi % (60 * 180)
pi % 10800
1p1 % 10800 NB. 1p1 means pi
1p1 * (1 % 10800) NB. Re-express to take advantage of J's
constant hierarchy
(1 % 10800) * 1p1
1r10800 * 1p1
1r10800p1
See how expressive (effort-saving) a good notation can be?
'3.0' 8!:2 (,. 100 * 1 - %/)(,.&#&>~;:&.>) '1r10800p1' ; '(1%60) *
1p1%180'
1 9 89
9 16 44
A savings of almost 50% in characters, and 90% in words.
It gets even better when you consider the single-word version removes the
requirement for parenthesis and/or assignment, since the value is used more
than once, and always leftmost in an expression.
-Dan
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