# Assignment Operator

## `S[i] := x: List, RngIntElt, Elt`

Redefine the $i$-th term of the list $S$ to be $x$. If $i \leq 0$, then an error results. If $i = \#S + 1$, then $x$ is appended to $S$. Otherwise, if $i > \#S + 1$, an error results. Here $i$ is allowed to be a multi-index.