equivariant functions

[KennyTM~]

Andrei Alexandrescu wrote:
> Jason House wrote:
>> Andrei Alexandrescu Wrote:
>>
>>> ore-sama wrote:
>>>> Andrei Alexandrescu Wrote:
>>>>
>>>>> typeof(s) stripl(const(char)[] s);
>>>>>
>>>>> This signature states that it returns the same type as an
>>>>> argument. I propose that that pattern means stripl can accept
>>>>> _any_ subtype of const(char)[] and return that exact type.
>>>>> Inside the function, however, the type of s is the type
>>>>> declared, thus restricting its use.
>>>> this conflicts with current definition of typeof. Currently 
>>>> typeof(s) stripl(const(char)[] s); should be interpreted exactly
>>>> as const(char)[] stripl(const(char)[] s); it's unclear that
>>>> typeof here gets type of actual argument rather than parameter.
>>>> Currently typeof applies to parameter.
>>> That is correct.
>>>
>>> Andrei
>>
>> I've never understood the reuse of keywords for new meanings. I much
>> prefer new keywords for new concepts.
> 
> Even in natural language identical words are reused for various 
> different meanings. This suggests that people would not feel comfortable 
> with a very large vocabulary. The size of vocabularies varies 
> dramatically, but if you look closer you'll see that languages with 
> large vocabularies tend to have simpler grammars, suggesting that a 
> language's overall complexity is a constant-sum game.
> 
> In programming languages growing the vocabulary indiscriminately is 
> worse because it chews into the vocabulary available to user-defined 
> symbols.
> 
> Also, whenever a feature is to be integrated into the language, it is 
> preferable if possible to integrate it under an existing concept instead 
> of "allocating" a new concept to it.
> 
> 
> Andrei

Yes. That makes foreign English learners confusing the many uses of 
prepositions.

I think a programming language should not be like a natural language, 
but it must be precise enough to reduce ambiguity as much as possible. 
Overloading keywords with entirely different meaning is no good (scope, 
static, invariant).

(I think this is OK to use typeof in this feature, since you're really 
getting a type of something.)

-

BTW, the keyword problem exists because we chose to use /[_a-z]\w*/ to 
represent identifiers, which coincide with keywords. Perl and PHP, for 
example, uses /[$@*%][_a-z]\w*/ to represent variables, so the keyword 
problem can be somewhat diminished. Of course I'm not asking you to 
adopt this, as I hate those sigils too, but I'm just saying adding 
keywords can leave user identifiers alone.