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Re: Ternary operator patch

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On 16.09.2010 09:48, David Kastrup wrote:
> Jeff Pohlmeyer <yetanothergeek@gmail.com> writes:
> 
>> On Thu, Sep 16, 2010 at 2:20 AM, steve donovan wrote:
>>
>>> Just to be different, how about a pseudo-function
>>> choose(cond,val1,val2) with the appropriate lazy evaluation?
>>
>> pseudo?
>>
>> function choose(expr,yes,no)
>> if expr then return yes else return no end
>> end
> 
> That evaluation is inappropriately unlazy.
Right, it should call functions at check time, like this:
function choose(cond, yesfunction, nofunction)
 if cond then
 return yesfunction()
 else
 return nofunction()
 end
end
But then it should be called like:
choose(true, function() print('YES') end, function() print('NO') end)
or in general case:
choose(cond, yesfunction, nofunction)
More universal implementation would allow both functions and
booleans/others:
function choose(cond, yescase, nocase)
 if cond then
 if type(yescase)=='function' then
 return yescase()
 else
 return yescase
 end
 else
 if type(nocase)=='function' then
 return nocase()
 else
 return nocase
 end
 end
end
print (choose(false, yesfunction, 'Hello'))
So you no longer need a change in the language syntax.
Regards,
miko

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