`algo` doesn't work with more than 1 parameter

`algo` or `eval` doesn't work when it receives more than two parameters. For example:

```
let fn add(x,y N) N
know:
    forall x N: add(x, 0) = x
    forall x,y N: add(x, y) = add(x+1, y-1)

algo add(x, y):
    if y = 0:
        return 0
    if y > 0:
        return add(x+1, y-1)

eval(add(3, 2))  # should be equivalent to add(3, 2) = add(4, 1) = add(5, 0) = 5
add(3, 2) = 5
```