Yes, I just figured it out the same definition. However, I was very surprised to see perm massively outperforms tap:
timespacex 'a=: perm 10' 0.3946 3.18771e8 timespacex 'b=: (A.&:i.~ !) 10' 2.74118 5.62038e8 a-:b 1 JVERSION Engine: j901/j32/android Release-e: commercial/2020-02-09T15:23:16 Library: 9.01.24 J Android: 1.4.08/7.1.2/25 Platform: Android 32 (armeabi-v7a) Installer: unknown InstallPath: /storage/emulated/0/Android/data/com.jsoftware.j.android/files Contact: www.jsoftware.com Perhaps an opportunity for performance improvement in dyadic A. ? Best regards, Jan-Pieter On Mon, May 25, 2020, 22:59 'Mike Day' via Programming < [email protected]> wrote: > If I can’t remember the idiom, I look for “tap.” My favourite form is > tap =: A.&i.~ ! > > (perm-: tap)3. NB. Same results..... > 1 > > Cheers, > > Mike > Sent from my iPad > > > On 25 May 2020, at 21:44, Skip Cave <[email protected]> wrote: > > > > perm > > > > 3 : 0 > > > > z=. i.1 0 > > > > for. i.y do. z=. ,/ (0 ,. 1 + z) {"2 1 \:"1 = i. 1 + {: $z end. > > > > : > > > > ,/ ({~ perm@#)"1 x comb y > > > > ) > > > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
