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Date:Mon Jan 30 18:47:00 1998 
Subject:Re: Complexity 
From:Juliusz Chroboczek 
Volume-ID:980130.02 

In article <34ce2b2a.0@rcfnews.cs.umass.edu>, 
  pop@cs.umass.edu (Robin Popplestone) writes:

RP> Actually, my recollection is that Jensen's device was presented to
RP> me around 1964 as a -desirable- feature of Algol 60. Which,
RP> efficiency apart, it was 

[ example showing how to simulate downwards closures in ALGOL 60 snipped ]

I think I can confirm this.  By pure chance, I just have on my desk 
``A Primer of ALGOL 60 programming'' by E. Dijkstra, January 1962.
This is a translation of an earlier book in Dutch, so I suppose this
is as close to the beginning of time as one can get.  Chapter 20
(``Bound variables'') starts with the following words:

    We should like to draw the reader's attention to an ingenious way
    of using formal parameters not included in the value list.  As
    far as we know it was first discovered by J. Jensen, and it is
    therefore called `Jensen's device'.  In the first place, it is a
    good test to see whether one has grasped the full implications of
    the concept of the `formal parameter'; in the second place, one is
    introduced to a way of ALGOL programming that has already proved
    to be extremely useful. 

Dijkstra then proceeds to give the standard `SIGMA' example.

By the way, does anyone know who J. Jensen is?


                                        J.