Structural Induction Example
lappend([], M) => M;
lappend([A | L], M) => [A | append(L, M)];

lShow
("L) ("M)
  length(append(L, M)) = length(L) + length(M)

lHere P(L) is the property:

 ("M) length(append(L, M)) = length(L) + length(M)