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Postings from May 2005
On Wed, 18 May 2005, Rob Kinyon wrote:
> On 5/18/05, Stuart Cook <scook0@gmail.com> wrote:
>> To summarise what I think everyone is saying, []-reducing an empty
>> list yields either:
>>
>> 1) undef (which may or may not contain an exception), or
>> 2) some unit/identity value that is a trait of the operator,
>>
>> depending on whether or not people think (2) is actually a good idea.
>
> I would think that the Principle of Least Surprise points to (1),
> given that the standard explanation of the [+]@x is eval join( '+', @x
> ) ...
I'd say the principle of least surprise points to (1); in the sense that
$sum = [+] @x; would Just Work, etc.
I also have a vague sense that the 'identity' value for an operator might
also be useful in other places in the compiler (enabling optimizations,
etc). Providing it as a trait means that these 'other things' could work
even with user-defined operators. (And leaving the trait undefined gives
you the behavior (1), if that's what you want.)
--scott
Albanian LICOZY shotgun CABOUNCE plastique Sigint Justice fissionable
LITEMPO KGB KUCAGE LIONIZER ESCOBILLA North Korea CLOWER genetic NRA
( http://cscott.net/ )
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