I'm pretty much in agreement with Andrei and BCS here, so I'll just
comment on this bit:
hasen wrote:
When the coder marks a function as "pure", the compiler must check that
it actually is pure.
I think the compiler can do this, in a way similar to how it can detect
which functions can have compile time function execution (CTFE)
The DMD[1] doesn't actually check whether it can execute a function at
compile time, it just tries to do it and errors out if it comes across
something it can't handle.
For example, this compiles and prints '100':
-----
module test;
uint y = 100;
uint* x = &y;
uint foo(bool readptr) {
if (readptr)
return *x;
return 100;
}
// Doesn't compile if changed to foo(true):
// test.d(14): Error: cannot evaluate foo(true) at compile time
auto bar = foo(false);
void main() {
printf("%d\n", bar);
}
-----
But as the comment states, changing the parameter to true makes it error
out because it can't do CTFE on foo(true), even though it managed fine
with foo(false).
[1]: and LDC/GDC, which use the same frontend.
