Was this the expression?
expand =: (#~ 1 j. #;._1)~
'ab' -: 1 0 1 # 1 0 1 expand 'ab'
1
I found it on lines 5 6 of the file system\examples\phrases\phrc5.ijs :
1!:11 (jpath '~system\examples\phrases\phrc5.ijs');243 126
m3 =: 1: j. # ;. _1 NB. Real 1; Imaginary # of 0's
between 1's
d4 =: [EMAIL PROTECTED] # ] NB. Expand
Of course, if you just want to do in J what \ does in APL, use #^:_1 .
'ab' -: 1 0 1 # 1 0 1 #^:_1 'ab'
1
(-: ]&.(1 0 1&#^:_1)) 'ab'
1
By the way, b. can't return the inverses of dyads (the party line is that
dyads do not have inverses). But if you bond the dyad and use b. _1 , the
results sometimes can be informative:
1&#. b._1
($&1@>:@(1&(<[EMAIL PROTECTED]))@(1&>.)@(>./)@:|@, #: ]) :.(1&#.)
but not always:
1 0 1&# b._1
1 0 1&#^:_1
-Dan
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