On 7/31/2016 6:18 AM, BartC wrote:
The costs are near zero: at minimum, a syntactic construct such as:
repeat N:
that expands to:
for _ in range(N):
The benefit is not so much performance, but being able to express
something very easily and quickly.
The cost of the 'repeat' contraction is that one cannot use the loop
variable, either as part of a modified computation or for monitoring or
debugging purposes.
print(i, for_body_result)
Beginners are often atrocious at debugging, and it seems not to be
taught hardly at all. 'repeat n' erects a barrier to debugging.
Debugging: probing a computation to see what actually happens, as
opposed to what one wanted and expected to happen. (Me, just now ;-)
One major way of debugging is printing values as they are computed.
Naming values (objects) allows them to be printed without recomputing
the value. In the 'repeat n' context, recomputing would mean adding 3
lines of debugging code instead of 1.
i = 0
repeat n:
a = f(a)
print(i, a)
n += 1
As for the original topic: Guido judged that a uniform rule "Compound
statement headers end with ':' and the next line has an additional
indent" would make correct code easier to write and parse and make it
visually more obvious. Some Python aware editors like IDLE
automatically add the indent.
--
Terry Jan Reedy
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