On Sun, Jun 15, 2014 at 12:51:12PM -0700, Walter Bright via Digitalmars-d wrote: > On 6/15/2014 6:50 AM, Peter Alexander wrote: > >The fear of meta programming comes from Boost, and rightly so in > >my opinion. Boost is written with the assumption that users will > >never have to read its source code. When it comes to debugging > >and performance tuning however, that assumption is shattered. > > For years I avoided C++ templates (even though I implemented them in > DMC++) because they were just so dang hard to read. D originally was > not going to have templates for that reason. > > But I eventually discovered that hiding behind the complexity of C++ > templates was a very simple idea - templates are just functions with > compile time rather than run time arguments. (Isn't it amazing that I > could implement C++ without figuring this out? I still don't > understand that.) That was the enabling breakthrough for D templates.
I think you may have missed the fact that your very realization was a further development in itself. The term "template" comes from the C++ idea of having a pre-written piece of code with some blanks in a few places, that will be filled in to make the actual code. But the concept of "compile-time parameter" is something conceptually different, and more powerfully unifying IMO. It digs at the root of C++'s template nastiness, which ultimately comes from treating template parameters as something fundamentally distinct from function parameters. The ugly syntax is but the superficial expression of this underlying difference in conception. D's superior template syntax is not merely a better dressed syntax; it ultimately stems from treating template parameters as being the *same* thing as function parameters -- except they are evaluated at compile-time rather than runtime. This insight therefore causes D's templates to mesh very nicely with CTFE to form a beautifully-integrated whole. > In fact, templates engender such an "OMG! Templates! I don't get > Templates!" aura about them that I convinced Andrei to not even use > the word "template" in his book about D! [...] I like how TDPL introduces templates by not introducing them at all, but just talks about compile-time arguments. By the time the reader gets to the chapter on templates, he's already been using them comfortably. But on that note, perhaps it's not altogether a bad thing for the word "template" to have a negative connotation; perhaps we should be pushing the term "compile-time parameter" instead. It engenders an IMO superior way of thinking about these things that may help newcomers overcome the fear of metaprogramming. T -- MACINTOSH: Most Applications Crash, If Not, The Operating System Hangs
