/* Function that decomposes te number into a list */
decompose(N) := block(
    digits: [],
    while N > 0 do
    (remainder: mod(N, 10),
    digits: cons(remainder, digits),
    N: floor(N/10)),
    digits
)$

/* Function that given a number returns the sum of their digits */
sum_squares_digits(n):=block(
    decompose(n),
    map(lambda([x],x^2),%%),
    apply("+",%%))$

/* Predicate function based on the task iterated digits squaring */
happyp(n):=if n=1 then true else if n=89 then false else block(iter:n,while not member(iter,[1,89]) do iter:sum_squares_digits(iter),iter,if iter=1 then true)$

/* Test case */
/* First eight happy numbers */
block(
    happy:[],i:1,
    while length(happy)<8 do (if happyp(i) then happy:endcons(i,happy),i:i+1),
    happy);