[REBOL] Re: Loop with negative count
From: tim-johnsons:web at: 27-Dec-2006 19:20
* Peter Wood <pwawood-gmail.com> [061227 18:08]:
> Tim
>
> Why don't you protect your code against changes in undocumented
> behaviour by either using:
Thanks. Of course.
Also it could be redefined probably with some
performance penalty.
loop: func[count[integer!] code[block!]][
if positive? count[
system/words/loop count code
]
] ;; untested and "unbenchmarked", but not
;; "unfooledaroundwith" :-)
> Loop max 0 possible-negative-count
> or
> if positive? count [loop count [code]]
>
> I thought that there would be a time penalty in doing so but my tests
> show it is hardly noticeable. (Providing my tests are correct).
>
> Regards
>
> Peter
>
> Test Source:
> REBOl []
>
> count: to integer! ask "Enter an integer - positive of negative: "
> times: 100000
>
> start: now/time/precise
> loop times
> [
> test: copy []
> loop count [append test "hello"]
> ]
> end: now/time/precise
> print "test 1"
> print [times "loops with count of " count " took: " subtract end start]
>
> start: now/time/precise
> loop times
> [
> test: copy []
> loop max 0 count [append test "hello"]
> ]
> end: now/time/precise
> print "test 2"
> print [times "loops with count of " count " took: " subtract end start]
>
> start: now/time/precise
> loop times
> [
> test: copy []
> if positive? count [loop count [append test "hello"]]
> ]
> end: now/time/precise
> print "test 3"
> print [times "loops with count of " count " took: " subtract end start]
>
> >> do %tt.r
> Script: "Untitled" (none)
> Enter an integer - positive of negative: 2
> test 1
> 100000 loops with count of 2 took: 0:00:02.404771
> test 2
> 100000 loops with count of 2 took: 0:00:02.365083
> test 3
> 100000 loops with count of 2 took: 0:00:02.41553
> >> do %tt.r
> Script: "Untitled" (none)
> Enter an integer - positive of negative: 8
> test 1
> 100000 loops with count of 8 took: 0:00:08.297555
> test 2
> 100000 loops with count of 8 took: 0:00:07.476637
> test 3
> 100000 loops with count of 8 took: 0:00:07.236025
> >> do %tt.r
> Script: "Untitled" (none)
> Enter an integer - positive of negative: -4
> test 1
> 100000 loops with count of -4 took: 0:00:00.843843
> test 2
> 100000 loops with count of -4 took: 0:00:00.683992
> test 3
> 100000 loops with count of -4 took: 0:00:00.466519
> >> do %tt.r
> Script: "Untitled" (none)
> Enter an integer - positive of negative: -55
> test 1
> 100000 loops with count of -55 took: 0:00:00.902979
> test 2
> 100000 loops with count of -55 took: 0:00:00.600534
> test 3
> 100000 loops with count of -55 took: 0:00:00.513414
> >> do %tt.r
> Script: "Untitled" (none)
> Enter an integer - positive of negative: 30
> test 1
> 100000 loops with count of 30 took: 0:00:37.077424
> test 2
> 100000 loops with count of 30 took: 0:00:33.583799
> test 3
> 100000 loops with count of 30 took: 0:00:38.293701
>
> > Hello:
> > on Core 2.6.2.4.2
> >
> >>> help loop
> > makes no reference to negative values for the 'count argument.
> >
> > consider the following console session
> >>> test: []
> > == []
> >>> loop -4 [append test "hello"]
> >>> test
> > == []
> >
> > Can we reliably expect that a negative argument will be ignored?
> > thanks
> > tim
> > --
> > Tim Johnson <tim-johnsons-web.com>
> > http://www.alaska-internet-solutions.com
> > --
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> > lists at rebol.com with unsubscribe as the subject.
> >
>
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--
Tim Johnson <tim-johnsons-web.com>
http://www.alaska-internet-solutions.com
