[TUHS] Book Recommendation

Douglas McIlroy douglas.mcilroy at dartmouth.edu
Wed Nov 17 03:00:52 AEST 2021

>> The former notation C(B(A)) became A->B->C. This was PL/I's gift to C.

> You seem to have a gift for notation. That's rare.  Curious what you think of APL?

I take credit as a go-between, not as an inventor. Ken Knowlton
introduced the notation ABC in BEFLIX, a pixel-based animation
language. Ken didn't need an operator because identifiers were single
letters. I showed Ken's scheme to Bud Lawson, the originator of PL/I's
pointer facility. Bud liked it and came up with the vivid -> notation
to accommodate longer identifiers.

If I had a real gift of notation I would have come up with the pipe
symbol. In my original notation ls|wc was written ls>wc>. Ken Thompson
invented | a couple of months later. That was so influential that
recently, in a paper that had nothing to do with Unix, I saw |
referred to as the "pipe character"!

APL is a fascinating invention, but can be so compact as to be
inscrutable. (I confess not to have practiced APL enough to become
fluent.) In the same vein, Haskell's powerful higher-level functions
make middling fragments of code very clear, but can compress large
code to opacity. Jeremy Gibbons, a high priest of functional
programming, even wrote a paper about deconstructing such wonders for
improved readability.

Human impatience balks at tarrying over a saying that puts so much in
a small space. Yet it helps once you learn it. Try reading transcripts
of medieval Arabic algebra carried out in words rather than symbols.
Iverson's hardware descriptions in APL are another case where
symbology pays off.


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