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Comment by zakirenish | Hacker News Reader

If you come to finance, most of the developers love premature templatization, it makes them feel like they know something. Not sure it that can be attributed to their insecurity about C++ coding skills, but it gets really ridiculous at times.

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I have a friend who runs a hedge fund, not really insecure at all but uses templates vigorously. More stuff in compile time rather than runtime. In critical sections inheritance can be prohibitively expensive because of the use of lookup tables.

Thrashing your I$ because you have too many template instantiations can be prohibitively expensive too, it's just harder to metric.

Just how many nested templates are we talking about here? You can have that problem (obviously) with or without templates. Most sane template designs don't exist when the program is actually run (Debugging them when they don't work is another matter)

if you're using templates for compile time computations it's maybe time for c++14 or even c++17 simpler constexpr functions (if possible and available, and if allowed to, ofc.)

I guess they start over each time the requirements change? :)

What does this have to do with the link?

What's wrong with using templates vigorously?

Well, let me give you an example that I have seen recently. There was this function that suppose to convert numeric value to string. So numeric type was templatized. Then with combination of enable_if and static_asserts there were checks to avoid doubles/floats negative numbers. So whats there left besides unsigned integers?

explicit overloads or concepts

Some things that are not so nice about templates:

- dozens to hundreds of compiler error lines for a single error, where it's hard to find out what the real problem is (IDEs often point to the wrong line)

- Code is hard to follow. E.g. try to figure out from boost asio source code which code is actually used if if you do a async_read(socket). I personally gave up after the second level of template substitutions, and have only a chance to follow the execution path in the debugger.

- Besides goto definition also other IDE features do not work really well with templates. E.g. no autocompletions for constructors with make_shared.

All three of these seem to be compiler/tool UI problems and not problems with templates themselves.

D has templates, yet their error messages seem fine for debugging what's going on.

That's because D's standard library doesn't use templates in the same way as the STL (No iterators, less policies). Also, D has is actually vaguely modern and has proper static reflection, static asserts and static if: Writing template constraints is easy, unlike C++ (even with Concepts/-lite)

As a bonus you can meditate deeply on all conseqences of using tempates in the vastly increased compilation time that they are going to introduce.

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