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Glossary of APL terms

APL literature includes many terms whose meanings, though rigorous, differ slightly from elsewhere. Terms used but not defined here follow normal usage or are defined at FOLDOC¹.

Term	Description
ambivalent	(or nomadic²)(of a dyadic function) permitting its left argument to be elided.
argument	value or reference passed to a function or operator.
array	(or variable) data valued object of zero or more orthogonal dimensions in row-major order in which each item is a primitive scalar or another array.
cell	(of an array) sub-array whose dimensions are a suffix of those of the whole. The 2-cells of a 3D array are the planes whose dimensions are the numbers of rows and columns of the 3d array.
define	create by lexical assignment³ or association⁴ or in an editor⁵.
depth	(of an array) the number of levels of nesting.
derive	create by juxtaposition as a combination of one or two existing arrays or functions with an operator⁶.
dyadic	accepting or requiring two arguments or operands: left and right; having valence of two.
element	(of an array) sub-array being a simple scalar at whatever depth. The elements of a simple array are also its items.
empty	(or null)(of an array) having one or more dimensions of length zero.
enclose	(of an array) convert into a scalar preserving all the original structure. An enclosed array can occupy a single position in another array.
function	primitive, defined, derived or system operation or mapping that takes zero, one (right) or two (left & right) array valued arguments and may return an array valued result.
item	(of an array) sub-array, which may be enclosed, occupying a single position in the outer structure of the array. The items of a simple array are also its elements.
matrix	(of an array) having two dimensions. (of a function) applying to matrices.
monadic	accepting or requiring one argument or operand; on the right for a function; on the left for an operator; having valence of one.
nested	(of an array) having one or more items or a prototype which is not a primitive scalar.
niladic	accepting no arguments; having valence of zero.
operand	argument to an operator.
operator	primitive or defined operation or mapping that takes one (left) or two (left & right) function or array valued arguments (operands) and derives a function.
pervasive	(of a function) applying equally to scalars at any depth.
prototype	(of an array) the type of its first item.
rank	(of an array) number of dimensions. (of a function) ranks of arguments to which it applies.
reduction	application of a function between the items of its right argument thus reducing the rank by one.
scalar	(of an array) having zero dimensions. (of a function) applying to scalars. (- extension) replication of a scalar argument to the shape of the other.
shape	(of an array) length of each dimension.
simple	(of a scalar) a single primitive datum. (of an array) composed entirely of primitive scalars.
strand	lexical juxtaposition of array valued names or expressions to form a larger, possibly nested, array⁷.
type	(of an array) array of identical structure in which all numbers are zero and all characters are blanks.
valence	degree or number of arguments or operands of an operation.
vector	(of an array) having one dimension. (of a function) applying to vectors.
workspace	area of computer memory containing arrays and defined &/or derived operations or a file containing a preserved binary image of such.

-- PhilLast 2009-10-05 14:55:22

CategoryAboutApl

FOLDOC: see The Free On-Line Dictionary Of Computing, Editor Denis Howe (1)
nomadic: see APLX concepts (2)
define by lexical assignment: assigned←{expression in terms of ⍺ and/or ⍵} (3)
define by lexical association: ⎕FX 'r←a associated w' 'r←expression in terms of a and/or w' (4)
define in an editor: ∇edited or )EDIT edited (5)
derive: derived←∘.,/∘(⍳¨) (6)
strand: stranded←0(1 2)('three' 'four')'five' (7)

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-||<rowclass="even">''element''   ||(of an array) sub-array being a ''simple scalar''; a primitive datum; at whatever ''depth''. The ''elements'' of a ''simple array'' are also its ''items''.||
+||<rowclass="even">''element''   ||(of an array) sub-array being a ''simple scalar'' at whatever ''depth''. The ''elements'' of a ''simple array'' are also its ''items''.||