x.sizeof vs typeid(x)

[bearophile]

Tom S Wrote:
> Well then, the whole C++ committee is following bad practice as well, by 
> making << and >> work with streams.

Right, a committee too can take bad choices, that operator usage is very unnatural, and it will always be for a C-based language. Operator overloading is useful, but like with all the situations where you have more power, you need more control too (this will become very clear when D will have macros. They will require a very strong self-discipline from the programmer, otherwise they will lead to big problems, mostly at the level of *language community*, and not at the level of single program. I have explained this in my 4th post of notes). So you have to use them avoiding to change their original semantics too much. Otherwise code becomes a jungle that a different programmer can't read well. As far as I know Java outlaws operator overloading essentially to avoid that class of problems. Java success comes from it being good for the *community* of Java programmers, and not just for the single programmer. Making the language simple and regular allows everyone to understand code written by others, and modify it, share it, etc. It also allows firms to take young programmers and use them to manage legacy Java code, etc, it allows to *lot* of less good programmers to use the language, like most of the people that today are using Processing, a graphics processing language that is essentially Java with few libs and some added sugar.

You can also read this section, it says right things:
http://en.wikipedia.org/wiki/Operator_overloading#Criticisms

Other languages don't outlaw it, like Python (despite giving less possibilities of op overload to help keep things more tidy). But you have to remember that generally even if something isn't outlawed it doesn't mean it's better for everyone to use it all the time. You don't have to use op overload *too much*. And you need some programming experience to know what "too much" means in a specific context. In this context program readability is more important that reducing the code to 2 lines instead of 4 without too much op overload. 

Note that DSL (Domain Specific Language) isn't something mostly for scripting languages, they come from Lisp (and Forth too, probably) that can be compiled into a normal executable. D with macros will be fit for that too.

Bye,
bearophile