property _genv
property _genf

-- @constructor
on new (me, genv, genf)
    me._genv = genv
    me._genf = genf
    return me
end

on exec (me, input)
    repeat while TRUE
        me._genv.exec(input)
        v = input[1]
        ok = TRUE
        me._genf.reset() -- reset filter generator
        repeat while TRUE
            me._genf.exec(input)
            f = input[1]
            if f>v then exit repeat
            if f=v then
                ok=FALSE
                exit repeat
            end if
        end repeat
        if ok then
            input[1] = v
            exit repeat
        end if
    end repeat
    return TRUE
end

on skip (me, steps)
    repeat with i = 1 to steps
        me.exec([])
    end repeat
end

on reset (me)
    me._genv.reset()
    me._genf.reset()
end