Comment by menaerus

1 hour ago

> Rust is quite capable of expression templates, as its iterator adapters prove.

AFAIU iterator adapters are not quite what expression templates are because they rely on the compiler optimizations rather than the built-in feature of the language, which enable you to do this without relying on the compiler pipeline.

1 comment

menaerus

aw1621107 34 minutes ago

I had always thought expression templates at the very least needed the optimizer to inline/flatten the tree of function calls that are built up. For instance, for something like x + y * z I'd expect an expression template type like sum<vector, product<vector, vector>> where sum would effectively have:

    vector l;
    product& r;
    auto operator[](size_t i) {
        return l[i] + r[i];
    }

And then product<vector, vector> would effectively have:

    vector l;
    vector r;
    auto operator[](size_t i) {
        return l[i] * r[i];
    }

That would require the optimizer to inline the latter into the former to end up with a single expression, though. Is there a different way to express this that doesn't rely on the optimizer for inlining?