On Tue, Sep 23, 2014 at 11:25:52PM +0000, deadalnix via Digitalmars-d wrote: > On Tuesday, 23 September 2014 at 20:22:32 UTC, H. S. Teoh via > Digitalmars-d wrote: > >SFINAE is another dark corner of disaster waiting to happen, once we > >decide to implement C++ template compatibility. As well as Koenig > >lookup, which will become indispensible if D code is to actually use > >non-trivial C++ libraries. > > > > We don't need these to be compatible with C++. We don't want to > be able to cut/paste C++ into a . file and expect it to compile, > but that you can map a reasonable amount of C++ constructs and > expect them to interact with the C++ code and back.
You *will* need SFINAE if you expect to interface C++ template libraries with D. Imagine that an existing codebase is using some C++ template library that depends on SFINAE. You'd like to start migrating to D, so you start writing new code in D. Eventually you need to make use of the C++ template library in order to interface with the C++ parts of the code, so you write a .di that declares template functions in an extern(c++) block. It works... some of the time. Other times you start getting weird errors or the wrong functions get called, because the C++ template library was written with SFINAE in mind, but D doesn't have that. So at the end of the day, it's a gigantic mess, and you go crawling back to C++. Unless, of course, we draw the line at templates and say that we won't support template compatibility with C++ (and I'd fully support that decision!). But that means we throw all C++ template libraries out the window, and any C++ codebase that makes heavy use of a template library will have to be rewritten from scratch in D. As for Koenig lookup, you might run into problems if you declare C++ wrappers for D functions in the C++ part of the codebase, and suddenly the wrong D functions are getting called due to Koenig lookup in C++ which wasn't considered when the D part of the code was written. T -- Без труда не выловишь и рыбку из пруда.
