On 4/30/2018 4:00 PM, Jeff Allen wrote:
They were not "statements", but "formulas" while '=' was assignment (sec
8) *and* comparison (sec 10B). So conversely to our worry, they actually
wanted users to think of assignment initially as a mathematical formula
(page 2) in order to exploit the similarity to a familiar concept,
albeit a=a+i makes no sense from this perspective.
When explaining iterative algorithms, such as Newton's method,
mathematicians write things like a' = a+1 or a(sub i+1 or sub new) =
f(a(sub i or sub old)) . For computer, we drop the super/subscript. Or
one can write more circuitously,
anew = update(aold)
aold = anew
The abbreviations should be explained when teaching loops.
For proving that the body of a loop maintains a loop constant, one may
reinstate the super- or sub-script.
--
Terry Jan Reedy
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