A little of Partial Compilation

[Walter Bright]

Don wrote:
> Note that even if all parameters to a function are known at compile 
> time, doesn't mean it's sensible to run it at compile time. (Example: 
> calculating pi to fifty billion decimal places). The programmer needs to 
> annotate it somehow to tell the compiler that is suitable for compile time.

It's one of those impossible problems for the compiler to predict if it 
should attempt to execute a function at compile time or not. That's why 
compile time function evaluation is initiated with a specific syntax, 
rather than tried in general.