Loops

Loops

Loops are quite common, but the standard way of making them is a bit difficult to read because the initial value is at the end while arguments are at the top.

(i) {
    exit_condition -> result
    ...
    @(i + 1)
} (0)

Often times we might want to modify something in the loop, but because it is a function, we have to pass it along:

(i, x) {
    exit_condition -> x
    ...
    @(i + 1, x)
} (0, initial_x)

idea 1

Have the initial values next to the arguments

(i := 0, x := initial_x) { ... }

idea 2

Create new loop syntax. This is not a new scope, so things we want to modify do not have to be passed along

> var := start
| some stuff
* exit condition
| these
|   don't
|     loop
^ conditionally loop back
| neither
|   this
^ unconditionally loop back

example (uses unimplemented array initialisation syntax):

fib := (n) {
    arr := [1, 1; n + 1]
    > i := 2
    | i > n -> arr[n]
    | arr[i] := arr[i - 1] + arr[i - 2]
    ^ i + 1
}