On Saturday, 3 September 2016 at 10:56:20 UTC, Tobias M wrote:
On Saturday, 3 September 2016 at 10:33:22 UTC, Walter Bright
wrote:
I don't think it is a template issue. It's a name lookup
issue. There's LINQ in C#, for example.
I think it is.
The problem is lookup of dependent symbols (see C++ two phase
lookup). Without real templates, all lookup can be done at
definition time.
I'm not very familiar with LINQ, but generally C# uses uses
interfaces as constraints on generics, similar to traits/type
classes. Lookup is then done once, considering only the
interfaces, not for each the concrete type.
No, LINQ doesn't work because of interfaces, but because of
extension methods (C#'s variant of UFCS). The IEnumerable<T>
interface defines only a single method. All the useful
functionality is implemented as extension methods which are only
available if the user specifically imports the namespace in which
where they're defined (just like D's ranges and range primitive
implementations for arrays). Those extension methods are used as
a fallback, similarly to UFCS in D: every type can override the
extension methods by implementing the method itself. Also more
inner namespaces (more closer to the method invocation) override
more outer namespaces. For more info see:
1)
https://github.com/ljw1004/csharpspec/blob/gh-pages/expressions.md#member-lookup Member Lookup
2)
https://github.com/ljw1004/csharpspec/blob/gh-pages/expressions.md#member-access Member access and
3)
https://github.com/ljw1004/csharpspec/blob/gh-pages/expressions.md#extension-method-invocations Extension method invocations
