Whatever is said should comply with Dictionary, esp. A. Nouns here http://www.jsoftware.com/help/dictionary/dicta.htm
In particular, I withdraw my earlier statement that atoms are non-arrays. Atom is used as alias in two senses, which is not contradictory and which one is determined by context: - rank-0 array - rank-0 cell I think "axis" is under-used in fear of connection with earlier APLs where operation modifiers were axis-based as opposed to rank-based. But the term "axis" does not change and is useful. So especially for people with other language background, more accustomed with "dimensions", the term "axis" should be prominently defined, illustrated and then used throughout. This is also better English three-dimensional array -- not three-axial array zero axis, axis 0 or leading axis -- not zero dimension element index -- not point coordinates J-specific shape of array -- not dimentions of array Phrase like rank is used to select atoms of array is very loose. What should be said is that rank determins cells, which is done by specifying _trailing_ axes, directly or a complement to array rank. I don't think it is possible to have "negative-cells". But _negative rank_ can be used to specify cells as complement to array rank. Like you cannot have negative number of people in the room, but you can use negative increase of people to reduce their number at most down to zero. Some terminology though is not very clear: list/vector and table/matrix. In Dictionary list is 1-array, i.e. having one-element shape. Frame is the shape for a selected cell-rank. When cells are of rank _1, they are called items, and the frame is one-elemet shape. So can we call it list? Then how we distinguished lists when the whole array is rank-1 ? Vectors? --- Raul Miller <[EMAIL PROTECTED]> wrote: > On 4/3/07, Terrence Brannon <[EMAIL PROTECTED]> wrote: > > getting solid theoretical underpinnings. I am going back through > > "Declarations" and building a crib sheet (it follows). And then I will > > move on with confidence through the next two sections. > > > > - 0-cell: this *is* an atom. this is *not* an array > > Er... please be careful here. Atoms are arrays. Cells > are not arrays in and of themselves (they often represent > arrays or array flavored arguments for element verbs in a derived > verb ... but I should probably leave that discussion for another > time.) > > Atoms are degenerate arrays. Alternatively, arrays are full > of atoms. Atoms have no dimensions -- and this means you > can't have different rank 0 arrays with different numbers of elements > -- you always have exactly one element in a 0 cell or a rank 0 array. > > But "cells" are not arrays. They are a mechanism for subdividing > an array. This becomes more clear when considering higher ranks > (see below). For the 0-cell case, it's almost a non-issue. > > > - 1-cell: rank-1 array, possibly containing 0 elements > > A 1 cell may be a rank-1 array, or a rank-0 array. > > rank=:[EMAIL PROTECTED] > rank"1 i. 3 4 > 1 1 1 > rank"1 'a' > 0 > > > - frame: a shape which, when the shape of the n-cell is concatenated, > > will yield the shape of the noun > > Yes. > > > - negative-cell: an n-cell where abs(n) is the frame length > > Close -- degenerate cases need a slightly different description. > Also, since n-cell typically indicates the maximum rank of the > cell, I'd also want to change that part of the description. > > But since this is a memory aid for you, I'll leave it to you to decide > on the best description. > > > > - If exactly one character is between the quotes, the value is an atom; > > if none or more than one, the result is a list. > > Yes. > > > - scalar == atom == rank 0 array > > - shape of 0 is for an array. an atom's shape is an empty list > > I can't quite parse "shape of 0 is for an array", but you seem to > have the basic idea. > > -- > Raul > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ____________________________________________________________________________________ It's here! Your new message! Get new email alerts with the free Yahoo! Toolbar. http://tools.search.yahoo.com/toolbar/features/mail/ ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
