0 = 0
        1 = 1
    0 + 1 = 1
    1 + 2 = 3
2 + 3 + 4 = 9

        0 = 0
        1 = 1
    0 + 1 = 1
    1 + 2 = 3
2 + 3 + 4 = 9

        0 = 0
        1 = 1
    0 + 1 = 1
    1 + 2 = 3
2 + 3 + 4 = 9

        0 = 0
        1 = 1
    0 + 1 = 1
    1 + 2 = 3
2 + 3 + 4 = 9

[] = concat([])
[] = concat([[]])
[] = concat([[],[]])
[] = concat([[],[],[]])
[1,2,3,4,5,6] = concat([[1,2,3,4,5,6]])
[1,2,3,4,5,6] = concat([[1,2,3,4,5,6],[]])
[1,2,3,4,5,6] = concat([[1,2,3],[4,5,6]])
[1,2,3,4,5,6] = concat([[],[1,2,3,4,5,6]])
[1,2,3,4,5,6] = concat([[1,2,3,4,5,6],[],[]])
[1,2,3,4,5,6] = concat([[1,2,3,4,5],[6],[]])
[1,2,3,4,5,6] = concat([[1,2,3],[4,5,6],[]])
[1,2,3,4,5,6] = concat([[1],[2,3,4,5,6],[]])
[1,2,3,4,5,6] = concat([[],[1,2,3,4,5,6],[]])
[1,2,3,4,5,6] = concat([[],[1,2,3,4,5],[6]])
[1,2,3,4,5,6] = concat([[],[1,2,3],[4,5,6]])
[1,2,3,4,5,6] = concat([[],[1],[2,3,4,5,6]])
[1,2,3,4,5,6] = concat([[],[],[1,2,3,4,5,6]])
[1,2,3,4,5,6] = concat([[1,2],[3,4],[5,6]])

[] = zipFun([],[])
[] = zipFun([],[a,b,c])
[] = zipFun([1,2,3],[])
[(1,a)] = zipFun([1],[a])
[(1,a)] = zipFun([1],[a,b,c])
[(1,a)] = zipFun([1,2,3],[a])
[(1,a),(2,b)] = zipFun([1,2],[a,b])
[(1,a),(2,b)] = zipFun([1,2],[a,b,c])
[(1,a),(2,b)] = zipFun([1,2,3],[a,b])
[(1,a),(2,b),(3,c)] = zipFun([1,2,3],[a,b,c])

[] = heads([])
[] = heads([[]])
[] = heads([[],[]])
[] = heads([[],[],[]])
[1] = heads([[1,2,3,4,5,6]])
[1] = heads([[1,2,3,4,5,6],[]])
[1] = heads([[],[1,2,3,4,5,6]])
[1] = heads([[1,2,3,4,5,6],[],[]])
[1] = heads([[],[1,2,3,4,5,6],[]])
[1] = heads([[],[],[1,2,3,4,5,6]])
[1,2] = heads([[1],[2,3,4,5,6],[]])
[1,2] = heads([[],[1],[2,3,4,5,6]])
[1,4] = heads([[1,2,3],[4,5,6]])
[1,4] = heads([[1,2,3],[4,5,6],[]])
[1,4] = heads([[],[1,2,3],[4,5,6]])
[1,6] = heads([[1,2,3,4,5],[6],[]])
[1,6] = heads([[],[1,2,3,4,5],[6]])
[1,3,5] = heads([[1,2],[3,4],[5,6]])

[] = heads([])
[] = heads([[]])
[] = heads([[],[]])
[] = heads([[],[],[]])
[1] = heads([[1,2,3,4,5,6]])
[1] = heads([[1,2,3,4,5,6],[]])
[1] = heads([[],[1,2,3,4,5,6]])
[1] = heads([[1,2,3,4,5,6],[],[]])
[1] = heads([[],[1,2,3,4,5,6],[]])
[1] = heads([[],[],[1,2,3,4,5,6]])
[1,2] = heads([[1],[2,3,4,5,6],[]])
[1,2] = heads([[],[1],[2,3,4,5,6]])
[1,4] = heads([[1,2,3],[4,5,6]])
[1,4] = heads([[1,2,3],[4,5,6],[]])
[1,4] = heads([[],[1,2,3],[4,5,6]])
[1,6] = heads([[1,2,3,4,5],[6],[]])
[1,6] = heads([[],[1,2,3,4,5],[6]])
[1,3,5] = heads([[1,2],[3,4],[5,6]])

f (x) = Prod(Var(x), Var(x))
f'(x) = Sum(Prod(Var(x), Number(1)), Prod(Var(x), Number(1)))

f (x) = x * x
f'(x) = x * 1 + x * 1
g (x) = 2 * x * x + 3 * x
g'(x) = 2 * x * 1 + x * (2 * 1 + x * 0) + 3 * 1 + x * 0
g (3) = 27
g'(3) = 15

ta(x) = x + 3
tb(x) = x + 3
tc(x) = x + 3
td(x) = x + 3
te(x) = 2 * x + 3
tf(x) = 2 * x + 3
tg(x) = 6 * x
th(x) = x^6

f4(x) = x^4 + 7 * x^3 + 20 * x^2 + 23 * x + 5
f3(x) = 4 * x^3 + 21 * x^2 + 40 * x + 23
f2(x) = 12 * x^2 + 42 * x + 40
f1(x) = 24 * x + 42
f0(x) = 24

f4(0) = 5 ok
f4(1) = 56 ok
f4(2) = 203 ok
f4(3) = 524 ok
f4(4) = 1121 ok

f3(0) = 23 ok
f3(1) = 88 ok
f3(2) = 219 ok
f3(3) = 440 ok

f2(0) = 40 ok
f2(1) = 94 ok
f2(2) = 172 ok

f1(0) = 42 ok
f1(1) = 66 ok

f0(0) = 24 ok