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:''This page is about array rank, a number associated with every array. For numbers associated with a function specifying its argument rank, see [[function rank]]. For the operator that applies a function at a given rank, see [[Rank (operator)]].'' | :''This page is about array rank, a number associated with every array. For numbers associated with a function specifying its argument rank, see [[function rank]]. For the operator that applies a function at a given rank, see [[Rank (operator)]].'' | ||
In the APL [[array model]], the '''rank''' of an array is the number of dimensions or [[Axis|axes]] in its structure, or the length of its [[shape]]. The traditional expression for the rank of an array <source lang=apl inline>A</source> is <source lang=apl inline>⍴⍴A</source>. Because this expression results in a one-element [[vector]] rather than a [[scalar]], it is idiomatic in languages with a [[Tally]] function to write <source lang=apl inline>≢⍴A</source> instead. | In the APL [[array model]], the '''rank''' of an [[array]] is the number of dimensions or [[Axis|axes]] in its structure, or the length of its [[shape]]. The traditional expression for the rank of an array <source lang=apl inline>A</source> is <source lang=apl inline>⍴⍴A</source>. Because this expression results in a one-element [[vector]] rather than a [[scalar]], it is idiomatic in languages with a [[Tally]] function to write <source lang=apl inline>≢⍴A</source> instead. | ||
Arrays are given names based on their rank: | Arrays are given names based on their rank: | ||