NextAction ->
Arg Input : Integer | String

When Input = 1 | Input = -1 | Input = 0 then
Return RelProc Input

When Input = '' then
Return RelProc 0

Else
Exit ERR_PARAMETER

/* * */

RelProc NextAction ->
Arg Input : Integer

When Input = -1 then
Return StepLeft ?

When Input = 1 then
Return StepRight ?

Else
Return (? : Return)
