# version current
# meh

fold = macro data a b:
    accum = null
    each v in $ get data:
        if accum == null:
            accum = v
        else:
            accum = call a accum b v
    accum

# version a
# excess parameters are treated as names to block,
# no need to adress them in macro definition
# inconsistent with 'each', e.g. each a b in sometable:
# would have to move names to the end to become consistent e.g. each sometable a b:

fold = macro data cb:
    accum = null
    each v in data:
        if accum == null:
            accum = v
        else:
            accum = cb accum v
    accum


# version b
# more control, uglier macro definition

fold = macro data a b cb:
    accum = null
    each v in (value data):
        if accum == null:
            accum = v
        else:
            # version b.0
            (name a) = accum
            (name b) = v
            accum = cb
            # version b.1
            accum = cb (bind a accum) (bind b v)
            # version b.2, would have to implement named parameters?
            accum = cb (a)=accum (b)=v
    accum

# version c
# fake type system

fold = macro (value data) (name a) (name b) cb: # last parameter is always a block
    # ...

# calling all of them

fold sometable a b:
    a + b