• Nathan S. (22/22) Feb 12 2018 For example in std.container.rbtree:
• rikki cattermole (2/24) Feb 12 2018 https://dlang.org/spec/template.html#TemplateThisParameter
• Nathan S. (3/4) Feb 12 2018 Cheers.
• Simen =?UTF-8?B?S2rDpnLDpXM=?= (41/63) Feb 12 2018 It's a template this parameter:

Nathan S. <no.public.email example.com> writes:

For example in std.container.rbtree:

---
     auto equalRange(this This)(Elem e)
     {
         auto beg = _firstGreaterEqual(e);
         alias RangeType = RBRange!(typeof(beg));
         if (beg is _end || _less(e, beg.value))
             // no values are equal
             return RangeType(beg, beg);
         static if (allowDuplicates)
         {
             return RangeType(beg, _firstGreater(e));
         }
         else
         {
             // no sense in doing a full search, no duplicates are 
allowed,
             // so we just get the next node.
             return RangeType(beg, beg.next);
         }
     }
---

rikki cattermole <rikki cattermole.co.nz> writes:

On 12/02/2018 8:35 AM, Nathan S. wrote:
 For example in std.container.rbtree:
 
 ---
      auto equalRange(this This)(Elem e)
      {
          auto beg = _firstGreaterEqual(e);
          alias RangeType = RBRange!(typeof(beg));
          if (beg is _end || _less(e, beg.value))
              // no values are equal
              return RangeType(beg, beg);
          static if (allowDuplicates)
          {
              return RangeType(beg, _firstGreater(e));
          }
          else
          {
              // no sense in doing a full search, no duplicates are
allowed,
              // so we just get the next node.
              return RangeType(beg, beg.next);
          }
      }
 ---

https://dlang.org/spec/template.html#TemplateThisParameter

Nathan S. <no.public.email example.com> writes:

On Monday, 12 February 2018 at 08:42:42 UTC, rikki cattermole 
wrote:
 https://dlang.org/spec/template.html#TemplateThisParameter

Cheers.

Simen =?UTF-8?B?S2rDpnLDpXM=?= <simen.kjaras gmail.com> writes:

On Monday, 12 February 2018 at 08:35:05 UTC, Nathan S. wrote:
 For example in std.container.rbtree:

 ---
     auto equalRange(this This)(Elem e)
     {
         auto beg = _firstGreaterEqual(e);
         alias RangeType = RBRange!(typeof(beg));
         if (beg is _end || _less(e, beg.value))
             // no values are equal
             return RangeType(beg, beg);
         static if (allowDuplicates)
         {
             return RangeType(beg, _firstGreater(e));
         }
         else
         {
             // no sense in doing a full search, no duplicates 
 are allowed,
             // so we just get the next node.
             return RangeType(beg, beg.next);
         }
     }
 ---

It's a template this parameter:
https://dlang.org/spec/template.html#template_this_parameter

Simply put, it gets the type of the 'this' parameter when the 
function is invoked, with all type modifiers. For a class A with 
a subclass B, 'This' would be B if called from B, and const(A) 
when called from const(A).

The type of the 'this' parameter is the statically known type, 
not the dynamic type. This creates some limitations, as shown 
below.

Some examples:

struct S {
    void foo(this This)() {
        writeln(This.stringof);
    }
}

class A {
     void foo(this This)() {
         writeln(This.stringof);
     }
     void bar() {
         foo();
     }
}

class B : A{}

unittest {
     S s;
     const shared S css;
     immutable S iss;
     s.foo(); // S
     css.foo(); // shared(const(S))
     iss.foo(); // immutable(S)
     B b = new B();
     A a = b;
     b.foo(); // B
     a.foo(); // A, since typeof(a) == A.
     b.bar(); // A, since bar() calls foo() in a context where the 
type of 'this' is A.
}

--
   Simen