Building C++ modules

[Walter Bright]

On 8/13/2019 9:32 AM, H. S. Teoh wrote:
> So you see, the seemingly insignificant choice of <> as template
> argument list delimiters has far-reaching consequences.  In retrospect,
> it was a bad design decision.
There were some who warned about this from the beginning, but they were 
overruled. There was a prevailing attitude that implementation complexity was 
not relevant, only the user experience.

Another parsing problem exists in C as well:

   A * B;

Is that a declaration of B or is it a multiply expression? It cannot be 
determined until the compiler knows what A is, which requires semantic analysis.

You might think D has the same problem, but I added a simple rule to D:

   "If it can be parsed as a declaration, it's a declaration."

Which means A*B; is always a declaration, even if A is later determined to be a 
variable, in which case the compiler gives an error.

The reason this works is because A*B; is an expression with no effect, and hence 
people don't write such code. You might then think "what if * is an overloaded 
operator with side effects?" There's another rule for that, and that is 
overloading of arithmetic operators should be to implement arithmetic, which 
shouldn't have side effects.

(If you absolutely must have operator overloading, you can write (A*B); but such 
is strongly discouraged.)

The fact that in 20 years pretty much nobody has noticed that D operates this 
way is testament to it being the correct decision and it "just works".