On Sep 4, 2012, at 4:53 PM, Jim - FooBar(); wrote:
> On 04/09/12 21:02, Andy Fingerhut wrote:
>>
>> Stuart Halloway mentioned the idea of having two kinds of set/map
>> constructor functions, one kind which quietly eliminates duplicates, another
>> which throws an exception on duplicates.
>
> Is this not a source of inconsistency? are there performance issues involved?
> why not the correct thing on both/all cases?
I think the question arises more naturally for maps than for sets.
If someone types in the literal map {:a 5 :b 10 :c 13 :a -5}, what is the
"correct thing"?
Some people might be thinking the correct thing is "I want the last key :a's
value, -5, to win always, no matter if the key :a occurs more than once. I
never want an error for code like this."
Others might be thinking "Oh, that is obviously a typo in my source code. I
never intentionally want to specify the same key twice in any literal map. I
want the compiler to flag that as an error so I don't have to spend lots of
testing/debugging time to find that typo."
Personally, I can see both of those points of view as reasonable.
Either there needs to be a configurable knob to select the behavior, or one
group of people is happy, and the other are not.
Andy
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