Transitive const sucks (pure)

[Ingo Oeser]

Bruce Adams wrote:

> I not sure whether pure functions can modify class variables. 

I hope not!

> The 
> presentation states that they can't modify anything reachable through
> their arguments. 

They are like mappings (e.g y = f(x) ) in math.

If you write sth. like this:
b = foo;
for(i = 0; i < rand_range(1,1000); i++) {
  a = pure_func(b);
}
writefln("%s", a);

b will still contain foo and a will always have the same value in every
program run. pure_func will only be called once here. This is the possible
compiler optimisation, if pure_func() is a pure function.


Best Regards

Ingo Oeser