D does not support logical const due to the weak guarantees that it
provides.
So, without logical const, how are D users supposed to provide lazy
evaluation and memoization in their interfaces, given that the interface
should *seem* const, e.g.
class Matrix
{
double getDeterminant() const { /* expensive calculation */ }
}
If it turns out that getDeterminant is called often with the raw matrix
data remaining unchanged, how can we add caching to this class without
rewriting the const-ness of all code that touches it?
And how do we write generic code when it's practically impossible to
determine const-ness from a glance? e.g. getDeterminant looks like it
should be const, but wouldn't be if it had caching, so writing generic
code that uses getDeterminant would be very difficult.
