A primitive operator is a kind of operator which is defined by the language. Like a primitive function, a primitive operator is written with a single glyph in APL but may use multiple characters in other languages. The one exception to the single-glyph rule is the Outer Product, which is written
∘.. While some dialects consider the outer product to be a case of the dyadic operator Inner Product with a Jot (which they interpret as
⊂⍬) as its left operand, others consider it to be a primitive monadic operator on its own.
Primitive operators have historically been very limited, a condition which has caused greater variety in modern operators than in functions as language designers have extended the scope of operators in different ways. Iverson notation did not have a unified concept of an operator, and considered everything which is now an APL operator to be a form of special syntax. APL\360 generalized the concept of an operator, but defined only a small number of them: reductions, scans, inner products, and outer products. These operators applied only to primitive functions.
|APL features |
|Built-ins||Primitives (functions, operators) ∙ Quad name|
|Array model||Shape ∙ Rank ∙ Depth ∙ Bound ∙ Index (Indexing) ∙ Axis ∙ Ravel ∙ Ravel order ∙ Element ∙ Scalar ∙ Vector ∙ Matrix ∙ Simple scalar ∙ Simple array ∙ Nested array ∙ Cell ∙ Major cell ∙ Subarray ∙ Empty array ∙ Prototype|
|Data types||Number (Boolean, Complex number) ∙ Character (String) ∙ Box ∙ Namespace|
|Concepts and paradigms||Conformability (Scalar extension, Leading axis agreement) ∙ Scalar function (Pervasion) ∙ Identity element ∙ Complex floor ∙ Total array ordering ∙ Tacit programming (Function composition, Close composition) ∙ Glyph|
|Errors||LIMIT ERROR ∙ RANK ERROR ∙ SYNTAX ERROR ∙ DOMAIN ERROR ∙ LENGTH ERROR ∙ INDEX ERROR ∙ VALUE ERROR|