pub fn ext_from_base_slice(&mut self, arr: &[Felt<C::F>]) -> Ext<C::F, C::EF> {
        assert!(arr.len() <= <C::EF as AbstractExtensionField::<C::F>>::D);
        let mut res = SymbolicExt::from_f(C::EF::zero());
        for i in 0..arr.len() {
            res += arr[i] * SymbolicExt::from_f(C::EF::monomial(i));
        }
        self.eval(res)
    }
Creates an ext from a slice of felts.
crates/recursion/compiler/src/ir/utils.rs