Re: Assigning part of indexed object

*To*: mathgroup at smc.vnet.net*Subject*: [mg119845] Re: Assigning part of indexed object*From*: Oleksandr Rasputinov <oleksandr_rasputinov at hmamail.com>*Date*: Sat, 25 Jun 2011 05:28:21 -0400 (EDT)*References*: <itsjn7$8u7$1@smc.vnet.net> <itv7ve$pbu$1@smc.vnet.net> <iu1tp3$9kr$1@smc.vnet.net>

Regarding consistency, it is worth noting that there is a problem with ReplacePart as a direct substitute for Set: m = Range[5]; ReplacePart[m, 1 -> 10] :> {10, 2, 3, 4, 5} but m[[1]] = 10 :> ( m = {10, 2, 3, 4, 5}; 10 ) :> 10 the following is thus a better solution than what I had posted previously: Unprotect[Set]; Set[sym_[[part_]], val_] := ( sym = ReplacePart[sym, part -> val]; sym[[part]] ); Protect[Set]; Now: Clear[m]; (* OwnValues will override DownValues *) m[1] = Range[5]; m[1][[1]] = 10 :> ( m[1] = {10, 2, 3, 4, 5}; 10 ) :> 10 which is consistent with other uses of Set. On Jun 24, 12:52 pm, "Fabrice P. Laussy" <fabrice.lau...@n0spam- gmail.com> wrote: > Dear all, > > Thanks for the solution. Supplemented with Oleksandr Rasputinov's fix: > > > Unprotect[Set]; > > Set[sym_[[part_]], val_] := sym = ReplacePart[sym, part -> val]; > > Protect[Set]; > > it works splendidly. > > In "some elements of Mathematica Design (1992)" [http://goo.gl/nm1tT], > Stephan Wolfram makes a point where one should resist the temptation to > design functions to do things that look natural for them to do, as they > could break dramatically later on. > > Here we have a clear case where Set seems it ought to work as redesigned by > Oleksandr. Is there any reason for this not being the default behaviour?