Re: Re: Question

*To*: mathgroup at smc.vnet.net*Subject*: [mg74922] Re: [mg74892] Re: Question*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Wed, 11 Apr 2007 02:00:09 -0400 (EDT)*References*: <ev51pb$ai7$1@smc.vnet.net> <200704100917.FAA07351@smc.vnet.net>

This does to seem to be so strange to me. Note that: expr[[1,1]][[{1,2}]] c11[d111,d112] which is, of course, documented. On the other hand: expr[[1,1,{1,2}]] means the same thing as expr[[1,1]][[{1,2}]], which, I think, is consistent, with the general way of working of Part (although I don't know of any explicit documentation for this). Andrzej Kozlowski On 10 Apr 2007, at 18:17, dh wrote: > > > Hi Peter, > > you are right , there is something very surprising concerning > "Part". I > > beg you to mention this to Wolfram, e.g. to Daniel Lichtblau. > > Consider the following expression that has one level less than yours, > > but will do to make the point: > > expr = a[ > > b1[c11[d111, d112, d113], c12[d121, d122, d123], c13[d131, d132, > d133]], > > b2[c21[d211, d212, d213], c22[d221, d222, d223], c23[d231, d232, > d233]], > > b3[c31[d311, d312, d313], c32[d321, d322, d323], c33[d331, d332, > d333]] > > ] > > Now expr[[1,1,1]] gives d111 what is expected. expr[[1,1,{1,2}]] does > > not give {d111,d112}, but c11[d111,d112]. Therefore, as soon as we use > > more than one index on the same level, the head of the level above is > > applied. I wonder if this is a bug or intention, I just can't imagine > > an application for this. Further, expr[[2,1,{1,2}]] gives: > > c21[d111,d112] and expr[[{1,2},1,{1,2}]] does the apply "trick" once > > again: a[c11[d111,d112],c21[d111,d112]] > > Hope this will help, Daniel > > > > > >> Hello Daniel, > >> thanks. It is quite a decision to apply the head to a list when >> talking about parts. > >> I would expect just a list of parts. > >> Still I am not able to predict what happens to: > >> Lambda0[[{1, 2, 3}, 1, {1, 2, 3}, 1]] > >> which gives: Lambda0[Lambda2[1, 1, 1], Lambda2[2, 2, 2], Lambda2 >> [3, 3, 3]] > >> What confuses me is: > >> Lambda0[[{1, 2, 3}, 1, {1, 2, 3}]] > >> which gives: Lambda0[Lambda2[Lambda3[1, 1, 1], Lambda3[1, 1, 2], >> Lambda3[1, 1, 3]], Lambda2[Lambda3[2, 1, 1], > >> Lambda3[2, 1, 2], Lambda3[2, 1, 3]], Lambda2[Lambda3[3, 1, 1], >> Lambda3[3, 1, 2], Lambda3[3, 1, 3]]] > >> So, I do not understand anything about these manipulations. > >> Can anyone explain these results? In one way or another I am >> wrongly focussed. > >> with frienldy greetings, > >> Peter van Summeren > >> > > >

**References**:**Re: Question***From:*dh <dh@metrohm.ch>