[Issue 11927] New: a good proposal

[d-bugmail at puremagic.com]

https://d.puremagic.com/issues/show_bug.cgi?id=11927

           Summary: a good proposal
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: galaxylang at gmail.com


--- Comment #0 from galaxylang <galaxylang at gmail.com> 2014-01-14 23:02:34 PST ---
1:>a normal dumb question is like this

auto    F()
{
}
auto C(alias A)()
{
    return    A();
}
auto B(A)()
{
    return    A();
}
int main(string[] argv)
{    
    C!F();
    B!F();//Error: template instance B!(F) does not match   
              // template declaration B(A)()    
    return 0;
}

this need change alias can accept syntax
alias B=expression;
i think C should change to B syntax,now we can talk about some enhancement

2:>lambda with template

int main(string[] argv)
{

    alias f=(x)=>x+1;
    f(1);
    f(1.0);
    return 0;
}

3:so lambda function can pass to it

auto    more(F)()
{
    return F(1)+1;
}
int main(string[] argv)
{

    alias f=(x)=>x+2;
    more!(f)();
}

4:>template designed to compile time computing const value and types ,alias and
pure function can compulate const ,
if a funtion only have function and types(without side effect values)just is a
template to compulate types

auto    type(bool selector,A,B)()
{
    alias type=selector?A:B;
}
auto isInt(T)()
{
    alias isInt=(T is int);
}
alias Fun=type(int,F1,F2);

//even more if we change syntax to 
auto    type(bool selector,A,B)
{
    alias type=selector?A:B;
}
auto isInt(T)
{
    alias isInt=(T==int);
}
alias Fun=type(int,F1,F2);

value and type campute now morge into one syntax,template keyword maybe would
lost it's work

5:>Further,side effect value and type can in one function
auto compute(T)(T i)
{
    static if(T is int)
      alias compute=1;
    else
      alias compute=1.0/i;
}

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