Roger's confidence that (a=: 100 (2}) a) is the best way is due to his knowledge that J has special support for this construct, provided the same name (viz. a) is used on both sides of the copula. Then it actually does in-place updating (even though, at face value, J syntax does not permit such a thing).
See the details at: http://www.jsoftware.com/jwiki/Vocabulary/curlyrt#dyadic ...down at the bottom under the heading: "Use These Combinations". All this is advanced stuff for a beginner. Considerations like those raised in this thread doubtless made Devon McCormick omit Amend } from his "Minimal Beginning J" proposal (7 days ago, thread: "J Kernel"), in favor of using }. and {. as Sebastian proposed. On Mon, Sep 8, 2014 at 4:51 PM, Jose Mario Quintana < jose.mario.quint...@gmail.com> wrote: > Linda wrote: > " > The verb is amend and the main issue is that you must separate 100 and 2 or > they become the list 100 2 > " > > Actually, amend (}) is an adverb and the verb is (2}). > > Roger wrote: > " > a=: 100 (2}) a > " > > The form that Roger gave makes that apparent: > > test=. 2} > type'test' > ┌────┐ > │verb│ > └────┘ > > > > > On Mon, Sep 8, 2014 at 11:13 AM, Linda Alvord <lindaalv...@verizon.net> > wrote: > > > The verb is amend and the main issue is that you must separate 100 and 2 > > or > > they become the list 100 2 > > > > 100 (2)} A=.i.5 > > 0 1 100 3 4 > > > > (100) 2} A=.i.5 > > 0 1 100 3 4 > > > > > > Linda > > > > -----Original Message----- > > From: programming-boun...@forums.jsoftware.com > > [mailto:programming-boun...@forums.jsoftware.com] On Behalf Of Roger Hui > > Sent: Monday, September 08, 2014 10:21 AM > > To: Programming forum > > Subject: Re: [Jprogramming] Replace one item of a list > > > > a=: i.5 > > a > > 0 1 2 3 4 > > a=: 100 (2}) a > > a > > 0 1 100 3 4 > > > > > > > > On Mon, Sep 8, 2014 at 7:18 AM, Sebastian <seb_fo...@arcor.de> wrote: > > > > > Hi, > > > > > > What is actually the best practice to replace one item of a list? > > > > > > The only way I know feels a bit complicated: > > > > > > a =: i. 5 > > > 0 1 2 3 4 > > > > > > > > > > > > (2 {. a), 100, (3 }. a) > > > > > > 0 1 100 3 4 > > > > > > > > > > > > Best regards, > > > > > > Sebastian > > > ---------------------------------------------------------------------- > > > For information about J forums see http://www.jsoftware.com/forums.htm > > > > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
