Fun with templates

[Manu]

I feel like it would be much better to do this with type deduction, than to
introduce new keywords and concepts...
Saying type deduction is hard is probably not accurate. It's either
possible, or impossible. If it's mechanically possible, then it's easy for
the compiler to do. If it's impossible (or ambiguous), then an error would
be thrown in those cases. I'm sure the compiler is capable of working out
if it's impossible and complaining.


On 6 July 2013 23:50, TommiT <tommitissari at hotmail.com> wrote:

> On Saturday, 6 July 2013 at 13:30:02 UTC, TommiT wrote:
>
>> Some more details of this proposed feature:
>>
>> inout(T) foo(inout T)(T a, T b)
>> {
>>     return var;
>> }
>>
>> void bar(inout T)(T a, T b)
>> {
>>     a = b;
>> }
>>
>> void main()
>> {
>>     const int con;
>>     immutable int imm;
>>
>>     foo(con, con); // OK (returns const int)
>>     foo(con, imm); // Error: returned inout(T) is ambiguous
>>
>>     bar(con, con); // OK
>>     bar(con, imm); // OK (no ambiguity because inout not used)
>> }
>>
>
> Another approach, if we wanted a different syntax, would be to add a new
> keyword 'mutable'. Like immutable overrides const, mutable would override
> both const and immutable:
>
> static assert(is(mutable(const(int)) == int));
> static assert(is(mutable(immutable(**int)) == int));
>
> Here's how it would look:
>
> T foo(T)(mutable(T) a, mutable(T) b)
> {
>     a = b = 123;
>     return a;
>
> }
>
> void main()
> {
>     const int con;
>     immutable int imm;
>
>     foo(con, con); // OK (returns const int)
>     foo(con, imm); // Error: T is ambiguous
> }
>
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