($\lambda$$A$,$l$,$n$,$z$. $l$[$n$]) $\in$ $A$:Type$\rightarrow$$l$:($A$ List)$\rightarrow$$n$:$\mathbb{Z}\rightarrow\downarrow$(0$\leq$$n$ \& $n$$<\parallel$$l$$\parallel$)$\rightarrow$$A$