AA literals/initialisation

[Manu]

On 12 January 2014 14:29, Orvid King <blah38621 at gmail.com> wrote:

> On Sat, 11 Jan 2014 22:08:25 -0600, Manu <turkeyman at gmail.com> wrote:
>
>  On 12 November 2013 18:09, Don <x at nospam.com> wrote:
>>
>>>
>>> On Monday, 11 November 2013 at 11:39:06 UTC, Daniel Murphy wrote:
>>>
>>>
>>>> "Manu" <turkeyman at gmail.com> wrote in message
>>>>
>>>> news:mailman.355.1384158631.9546.digitalmars-d at puremagic.com...
>>>>
>>>>
>>>>> immutable string[string] priorityMap = [
>>>>>
>>>>> "1" : "blocker",
>>>>>
>>>>> "2" : "critical",
>>>>>
>>>>> "3" : "critical",
>>>>>
>>>>> "4" : "major",
>>>>>
>>>>> "5" : "major",
>>>>>
>>>>> "6" : "major",
>>>>>
>>>>> "7" : "minor",
>>>>>
>>>>> "8" : "minor",
>>>>>
>>>>> "9" : "trivial" ];
>>>>>
>>>>>
>>>>>
>>>>> main.d(56): Error: non-constant expression ["1":"blocker",
>>>>> "2":"critical",
>>>>>
>>>>> "3":"critical", "4":"major", "5":"major", "6":"major", "7":"minor",
>>>>>
>>>>> "8":"minor", "9":"trivial"]
>>>>>
>>>>>
>>>>>
>>>>> This is tedious, how long has it been now?
>>>>>
>>>>> Seriously, static map's are super-important, they should be able to be
>>>>> made
>>>>>
>>>>> immutable, and also be able to be initialised.
>>>>>
>>>>>
>>>>>
>>>>> Maybe this could be factored into the improvements for 2.065?
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>> I think yes, it can be done for 2.065.  Someone remind me if we get
>>>> close
>>>>
>>>> and it isn't done yet.
>>>>
>>>>
>>>
>>>
>>>
>>>
>>> IIRC the poor performance of array literals and AA literals is because
>>> they're not always >>literals, sometimes they are variables (!) and the
>>> compiler assumes the worst case. You are >>allowed to write:
>>>
>>>
>>>
>>> void foo(int some_param)
>>>
>>> {
>>>
>>>    immutable string[int] = [ 1: "abc", some_param: "def"];
>>>
>>> }
>>>
>>>
>>>
>>> I wish we could get rid of that silliness entirely.
>>>
>>>
>>>
>>>
>>>
>>> If the members are compile-time expressions, you probably want to mark
>>> the variable as static >>const/static immutable.
>>>
>>>
>> I've also had this thought. Logically, you shouldn't need to declare an
>> immutable thing static >(although currently, you do), although the
>> advantage would be a guaranteed compile error if you try >to do something
>> silly like initialise from a variable.
>>
>
> I would disagree with that statement, because it is my understanding of
> immutable that it merely means that the value is not modified after it is
> initialized, it does not however mean that the value is determinate at
> compile-time, nor that it is even the same in all invocations of a function.
>

If an immutable is initialised to a literal value, then there is no
possible way for variation to exist. It certainly is the same in all
invocations of the function, and there's no need to re-allocate+initialise
it on every call to the function.
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