Principled method of lookup-or-insert in associative arrays?

[Tyro[a.c.edwards]]

On 11/21/2010 10:39 AM, Tomek Sowiński wrote:
> Dnia 21-11-2010 o 02:02:35 Tyro[a.c.edwards] <nospam at home.com> napisał(a):
>
>>> The harm is confusion. Now = on arrays always means aliasing, but with
>>> your proposal, it may *sometimes* mean dupping. Imagine real-life code
>>> with type aliasing and type inference in play, and trying to determine
>>> whether some line makes a dupping string<->char[] conversion or not.
>>
>> alias char[] firstClassString;
>> alias firstClassString stringGold;
>> alias stringGold lightAtEndOfTunnel;
>> alias lightAtEndOfTunnel daBomb;
>> alias daBomb iAmThe;
>> iAmThe man;
>> if I want to know the actual type of shiznit:
>> writeln(typeid(man)); // outputs char[]
>>
>>> What would be the harm if everyone just put .(i)dup where it belongs?
>>
>> Actually, I don't see any harm in using .(i)dup. However, my limited
>> experience does not allow me to think on the same level as you so I'm
>> just trying to understand your point a little better. That being said,
>> I still don't understand the gravity of the implied problem.
>
> The status quo is imposing a tiny upfront tax on the writer of typing
> .(i)dup.
> The proposal is imposing a minor tax on the reader of knowing another
> rule and, in case of convoluted code like above, minor tax of
> determining if this rule applies. Plus, some tax on the implementor to
> put this rule into the compiler.

OK! Makes sense.

> The point is the aggregated tax imposed by the proposal is much greater
> because although minor it grows linearly with the number of readers
> (code is read much more often then written). And even with finite set of
> readers, the tax grows till infinity because with time people forget
> what they read, therefore the tax is collected anew.
>
> And think of the gains -- dropping .(i)dup doesn't really buy you much
> anyway.
>

Fair enough. Like I said, I'm not proposing that this happens. Just 
trying to understand why it shouldn't. Thanks for entertaining my questions.