List foldl := method(
    accu := first
    if(call message arguments size == 1,
        args := list(nil)
        meth := call message argAt(0) name
        slice(1) foreach(x, accu = accu performWithArgList(meth, args atPut(0, x)))
    ,
        aName := call argAt(0) name
        bName := call argAt(1) name
        body := call argAt(2)
        slice(1) foreach(x,
            call sender setSlot(aName, accu)
            call sender setSlot(bName, x)
            accu = call sender doMessage(body, call sender)
        )
    )
    accu
)

List foldr := method(
    accu := last
    if(call message arguments size == 1,
        args := list(nil)
        meth := call message argAt(0) name
        slice(0, -1) reverseForeach(x, accu = x performWithArgList(meth, args atPut(0, accu)))
    ,
        aName := call argAt(0) name
        bName := call argAt(1) name
        body := call argAt(2)
        slice(0, -1) reverseForeach(x,
            call sender setSlot(aName, x)
            call sender setSlot(bName, accu)
            accu = call sender doMessage(body, call sender)
        )
    )
    accu
)