It is my intention to include here other features of the early versions of J, as illustrated in my talk on The story of APL & J , at the J Conference, Toronto, October 2000


A crucial early step leading to the creation of the J language was Ken Iverson‘s chance acquisition of a second-hand copy of March & Wolff‘s Calculus, 1st Edition, 1917. Click here to display p.43, 57, 58 The sum, product, & quotient of two functions   (56KB)

i.e. (u + v) y  is   (u  y) + (v  y)  and, by extension,  x (u + v) y  is  (x u y) + (x v y)

This construction, which was introduced in the first version of J (1990), was invalid in APL. It is fully implemented in J as the fork and the related hook – the composition of two functions.

See:
Iverson, Kenneth E. and E. E. McDonnell, Phrasal Forms. Conference Proceedings APL89, ACM, New York, APL Quote Quad, vol.19, no 4, p.197-199.

Hui, Roger K.W., K.E. Iverson, E.E. McDonnell, Tacit Programming, APL91 Conference, Stanford, CA, Proceedings, APL Quote Quad, vol.21, no.4, p.202-211, ACM, New York

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