I have created a new class: HasSign. MElement now implements HasSign.
I have added another sample task to the sampleTasks list. Now there are two sample tasks.
I am working on the simplexChooseColmun and simplexChooseRow functions. simplexChooseColumn functions seems to be in a usable state by now. simplexChooseRow function is unfinished; it always returns zero, but at least it's compileable.