A Dictionary of APL

A Dictionary of APL is a 1987 paper by Ken Iverson that defines possible APL syntax and features. While allowances are made for "dialects" in comments, the paper primarily describes a simplified language similar to SHARP APL sometimes known as Dictionary APL. It introduces new primitives such as Nub Sieve, Nub In, Raze, Raze In, and functions for working with permutations, and aligns some functionality more closely with leading axis theory (however, the leading axis agreement that would later appear in J is not used). Much of this functionality was included in J's initial as described by the paper "APL\?" or added in later versions, but has largely not been introduced to APL implementations, with the exception of Nub Sieve.

Another feature of the dictionary is its heavy use of terminology taken from English grammar, such as "noun" and "verb" rather than "array" and "function". This terminology was largely retained in J, where the initial definition and documentation was likewise named the "J Dictionary". K also uses the terms "noun", "verb", and "adverb" for grammar, but as its grammar is not determined by value types, these names exist alongside the term "function".