The question that comes to me is: can I use fork(x) outside of a bend?
Seems like probably not, there doesn't seem to be enough information in the 'argument' to this 'function' to do anything useful without the implicit context of the bend construct.
For that reason I think I'd prefer it if fork was a keyword (like 'bend' and 'when') rather than a 'function', just at the surface syntax level to give a clue it is something special.
I guess fork is a kind of 'magic' function that represents the body of the bend. It's a bit like a 'self' or 'this'.
At the moment this syntax is in a weird half-way point ...the underlying concept is necessarily functional but it's trying to look kind of like an imperative for-loop still.
I wonder if we couldn't just explicitly create a 'bendable' recursive function that can be 'bent' by calling it. But I guess it's like this because it needs to be tightly constrained by the 'when' and 'else' forms.
TBH the more I look at this example the more confusing it is. The other part I wonder about is the assigning of new values to tree var... can I set other local vars from outside the bend scope? I don't think so, I guess it'd be a syntax error if the var names assigned in the 'when' and 'else' clauses didn't match?
Again it's sort of overloading an imperative-looking syntax to implicitly do the 'return' from the implicit recursive function.
Later on there is this example:
def render(depth, shader):
bend d = 0, i = 0:
when d
And here I wonder - does 'width' have a value after the bend? Or it's only the last assignment in each clause that is privileged?
That's an odd mix in a language which otherwise has explicit returns like Python.
If so I wonder if a syntax something like this might be clearer:
def render(depth, shader):
bend color with d = 0, i = 0:
when d
i.e. name the return var once in the bend itself, yield intermediate values (to itself, recursively) and return the final state.