Quickest way to remove item N in composite? (sysrpl)
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From: Virgil on 11 Jan 2010 01:46 In article <Virgil-4FAC6C.17565710012010(a)bignews.usenetmonster.com>, Virgil <Virgil(a)home.esc> wrote: > In article > <dbfcb94b-a6c0-4dbe-8780-d8cecaba22a4(a)j19g2000yqk.googlegroups.com>, > TW <timwessman(a)gmail.com> wrote: > > > I was fiddling with something today and found myself needing to remove > > an item from a list at a given index location and was surprised not to > > find a command that would do it. Am I missing one that is right in > > front of me? > > > > I was looking for something that would remove item N from a list, and > > preferably not modify the list if 0 < N or N >MAX_SIZE or something > > like that. It kind of surprised me I didn't see one. As a workaround I > > made a little routine that does a SUBCOMP on either side and puts them > > together, but that isn't very nice. . . > > > > TW > > Try this program with the list and the position, in that order, on the > stack: > > \<< \-> n > \<< 1 > \<< n NSUB == {DROP} IFT > \>> > DOSUBS > \>> > \>> > > Note that the program will not do anything when the list position is > below 1 or above the number of elements listed. I have found a much better program thatn the above to do the same thing. The one above misbehaves, leaving no set at all if you try to remove the first element from a one element set. Try the following short program with the list and the position to be deleted, in that order, on the stack: \<< DUP2 1 SWAP 1 - SUB UNROT 1 + OVER SIZE SUB + \>>
From: John H Meyers on 11 Jan 2010 20:39 Andreas Moeller: > exploding and rebuilding the composite is the fastest way in SYS-RPL Or even in UserRPL. The following (UserRPL) came from... (well, I forgot where): @ { list } N -> delete item N from list \<< SWAP LIST\-> 1 - DUP DUP 4 + ROLL - 3 + ROLL DROP \->LIST \>> Both SysRPL and 49/50 series UserRPL have a DUPDUP command, FWIW. Bounds checking is not included, but can be added. Another similar UserRPL version that's often been posted will accept a larger number N than the list size, yet not stop on error even if nothing else is initially on the stack. [r->] [OFF]
From: CesarV on 12 Jan 2010 10:07
On 10 ene, 16:49, TW <timwess...(a)gmail.com> wrote: > I was fiddling with something today and found myself needing to remove > an item from a list at a given index location and was surprised not to > find a command that would do it. Am I missing one that is right in > front of me? > > I was looking for something that would remove item N from a list, and > preferably not modify the list if 0 < N or N >MAX_SIZE or something > like that. It kind of surprised me I didn't see one. As a workaround I > made a little routine that does a SUBCOMP on either side and puts them > together, but that isn't very nice. . . > > TW You can use this The objects in the stack are showed at the rigth * Del the element of the position #i in the composite. * (#i is the position from the left) NULLNAME DelInComposite ( {} #i -> {}' ) :: DUP#0= ( {} #i flag ) 3PICK ( {} #i flag {} ) LENCOMP ( {} i# flag #len ) 3PICK ( {} i# flag #len i# ) #< ( {} i# flag flag' ) OR ( {} i# flag'' ) caseDROP ( {} ) ( exit of secondary ) ( {} i# ) SWAPINCOMP ( i# meta ) DUPDUP ( i# meta #n #n ) #3+ ( i# meta #n #n+3 ) ROLL ( meta #n #i ) #- ( meta #n-i ) #2+ ( meta #n-i+2 ) ROLLDROP ( ........ #n ) #1- ( meta' ) {}N ( {}' ) ; _____________________ César Vásquez Alvarado Lima Perú Visit the forum: http://honradoshp.foroactivo.com/ Visit my page: http://cesarv.jimdo.com/ |