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the logical operation confused me

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  the logical operation confused me length power <elearn2014@gmail.com> - 2014-04-11 07:02 +0800
    Re: the logical operation confused me Denis McMahon <denismfmcmahon@gmail.com> - 2014-04-10 23:28 +0000

#70069 — the logical operation confused me

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>>> "ok" or "not ok"
'ok'
>>> "ok" and "not ok"
'not ok'
>>>

why "ok" or "not ok" output "ok"  , "ok" and "not ok"  output "not ok" ?

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#70072

On Fri, 11 Apr 2014 07:02:33 +0800, length power wrote:

>>>> "ok" or "not ok"
> 'ok'
>>>> "ok" and "not ok"
> 'not ok'
>>>>
>>>>
> why "ok" or "not ok" output "ok"  , "ok" and "not ok"  output "not ok" ?

I believe that:

[ (falsey condition) or ]* (first truthy condition) or (any condition) 
[ or (any condition) ]*

will return (first truthy condition)

whereas:

(truthy condition) and [ (truthy condition) and ]* (last truthy condition)

will return (last truthy condition)

where "[ clause ]*" represents an optional clause that may be repeated 
any number of times, "any condition" may evaluate falsey or truthy, 
"first" and "last" relate to the position of the condition type in a left 
to right evaluation sequence.

-- 
Denis McMahon, denismfmcmahon@gmail.com

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