For “term one”, “term two”, “term three”, the expression
 is valid. If
y are valid expressions, then
[x,y] is also a valid expression, and the only valid expressions are built inductively using these two rules. For example,
[,[[,[,]],]] is a valid expression. The valid expressions represent terms in the language with one variable and one binary function symbol.
Check here to calculate and graph the output on every suffix of the input string.