Karim BELABAS on Tue, 19 Nov 2002 23:52:20 +0100 (MET) |
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Re: extension of vecextract() |
On Mon, 18 Nov 2002, Igor Schein wrote: > let's say I have a vector and I wanna insert an element into it: > > \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ > ? v=["a","b","c","d"]; > > \\ inserting an element at 3rd position: > > ? concat([vecextract(v,3),[1],vecextract(v,12)]) > ["a", "b", 1, "c", "d"] > \\ or > ? w=[1,2];concat([vecextract(v,w),[1],vecextract(v,eval(setminus(Set(vector(4,k,k)),Set(w))))]) > ["a", "b", 1, "c", "d"] > \\ or > ? concat([vecextract(v,"1..2"),[1],vecextract(v,"3..4")]) > ["a", "b", 1, "c", "d"] > > \\ however, if I wanna insert it in the beginning or in the end: > > ? concat([vecextract(v,15),[1],vecextract(v,0)]) > ["a", "b", "c", "d", 1] > \\ or > ? w=[1,2,3,4];concat([vecextract(v,w),[1],vecextract(v,eval(setminus(Set(vector(4,k,k)),w)))]) > ["a", "b", "c", "d", 1] > \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ > > There's no way to do it with ".." mechanism > > So maybe it's a good idea to extend ".." mechanism to be consistent > with the other two? I don't get it. What exact command would you like to run, and with what expected result ? [ Btw, what's wrong with concat(v, [1]), concat([1], v) ? ] Karim. -- Karim Belabas Tel: (+33) (0)1 69 15 57 48 Dép. de Mathématiques, Bât. 425 Fax: (+33) (0)1 69 15 60 19 Université Paris-Sud Email: Karim.Belabas@math.u-psud.fr F-91405 Orsay (France) http://www.math.u-psud.fr/~belabas/ -- PARI/GP Home Page: http://www.parigp-home.de/