Major cell: Difference between revisions

In the APL [[array model]] and [[leading axis theory]], a '''major cell''' is a [[cell]] of an array which has [[rank]] one smaller than the rank of the array, or equal to it if the array is a [[scalar]]. The number of major cells in an array is its [[Tally]], and a function can be called on the major cells of an array individually by applying it with rank <source lang=apl inline>¯1</source> using the [[Rank operator]]. Functions designed to follow leading axis theory often manipulate the major cells of an array. For example, [[Reverse First]] (<source lang=apl inline>⊖</source>) is considered the primary form of [[Reverse]] in leading-axis languages because it can be interpreted as reversing the major cells of its argument; [[J]] removes last-axis Reverse entirely.

Given another array <source lang=apl inline>B</source> we can search for cells of <source lang=apl inline>B</source> which [[match]] major cells of <source lang=apl inline>B</source>. [[High rank set functions|High-rank]] [[Index-of]] always searches for right argument cells whose rank matches the rank of a left argument major cell: if the right argument is a [[vector]] and not a [[matrix]] then it searches for the entire vector rather than its major cells (which are [[scalar]]s).

{{APL programming language}}