Why didn't it work? I think drowned in complexity...
Trying to understand/simplify what you said, I think something like
inc =: 4 : '(>: x.{y.) x.}y.'
dec =: 4 : '(<: x.{y.) x.}y.'
may be what you were getting at. e.g.
a =: 0 0 0 0 0 0 0 0
]a =: 3 inc a
0 0 0 1 0 0 0 0
5 2 inc^:4 a NB. increment items 5 and 2 - do it 4 times.
0 0 4 0 0 4 0 0
1 3 dec i. 5 6 NB. extends nicely, decrement rows 1 and 3.
0 1 2 3 4 5
5 6 7 8 9 10
12 13 14 15 16 17
17 18 19 20 21 22
24 25 26 27 28 29
- joey
At 22:20 -0500 2006/03/25, Nicholas Spies wrote:
To conceal some of the visual noise implicit in J, I (foolishly, no
doubt) tried to do the following:
NB. define an array in which to store data
a =: 0 0 0 0 0 0 0 0
NB. simple enough
get =: 4 : 'x.{ y.'
set =: 4 : '({. x.) (({: x.)}) y.'
]a =: 3 0 set a
3 0 0 0 0 0 0 0
]a =: 2 0 set a
2 0 0 0 0 0 0 0
NB. defining this was the whole point of my feeble efforts
inc =: 4 : '((>:(x. get y.))(x.) set y.)'
dec =: 4 : '((<:(x. get y.))(x.) set y.)'
NB. above gives an error
inc =: 4 : '( 1&+(x. get y.)),( x.) set y.'
dec =: 4 : '(_1&+(x. get y.)),( x.) set y.'
a
2 0 0 0 0 0 0 0
]a =: 0 inc a
1 0 0 0 0 0 0 0 0
NB. OK, it puts the 1: at the 0th position... but adds a zero
inc =: 4 : '( 1&+(x. get y.)),( x.) set y.'
dec =: 4 : '(_1&+(x. get y.)),( x.) set y.'
a =: b
a
0 0 0 0 0 0 0 0
]a =: 0 inc a
1 0 0 0 0 0 0 0 0
]a =: 0 inc a
2 0 0 0 0 0 0 0 0 0
]a =: 0 inc a
3 0 0 0 0 0 0 0 0 0 0
NB. in this case, incrementing works but the array lengthens...
Admittedly, trying to do this may be just plain foolish, but what's
the REAL way to do this?
Thanks,
--Nick
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