Untying The Gordian Knot: Agreement in J
Untying the Gordian Knot: Agreement in J
This paper from the 1995 APL conference in San Antonio explains how verbs work in J, in particular how verb rank works (without the rank conjunction!), and how this extends into combined/dervied verbs (via @, @:, or, suprise, ").
It is a bit lengthy but includes:
- the history of array processing rules across prior APL dialects
- pretty pictures
Section 12 reads a bit funny today. Back in 1995, functions such as *: Square or - Negate had unbounded monadic rank. This paper argued to give them scalar monadic rank, and this was done within the next year and made available for the first time with J Release 3.03, 1996 12 13 .
This version has one fix ("right" vs "left") and one wording improvement, but is otherwise the original paper.