> -----Original Message-----
> From: Wagner Lipnharski [SMTP:wagnerl@EARTHLINK.NET]
> Sent: Friday, 15 October 1999 0:26
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: Fw: Re: What's in the train? The whole story.
>
> Dave VanHorn wrote:
> >
> > > >  You may be able to prevent syntax error mechanicaly by keying the
> > blocks
> > > > such that a connection cannot be made between two operators for
> example.
> > > > This would simplify the code.  On the other hand, you may
> deliberately
> > > want
> > > > to allow syntax errors to improve the learning content of the toy.
> > >
> >  Tricky,  7 = 8 + -1 is legal.
>
> Legal combinations are +- -+ *- *+ /- /+, while ilegal are +/ +* -/ -*
> */ /*, and I think this should be resolved by software, since the skynny
> boy needs to learn what is valid and what isn't.
>
> All modules, digits or operators, need the GroundRet connector pin, even
> that at first impression you can think it is not necessary because
> operators can't be used at endings, this is only valid at the right side
> (3+2=5+), so the processing module should be installed at the left
> side.  But academic speaking, it is important to alert the skinny boy
> that "3=5+2-" is invalid, but yes at the left side as "-3=5-2", so in
> all instances the processor should be able to read back the ring, then
> all modules need the auto-loopback transistor.  Also different from what
> I thought at first, remember that more than one "=" module can be used
> at the equation, as "-6+14=5+3=10-2=7+1=24/3=2*4=-13+70/10+14=8"
>
> Wagner.
>
>
        If multiple '=' signs are allowed then the controller *MUST* be a
separate *MASTER* block.  If so then the possibility of varying 'grades' of
master arises, with differing features, giving rise to a whole range of
incremental maths machines (sort of like Ford sells small cars, large cars,
small trucks and large trucks).

        I say create a definate master block with an LCD display panel that
gives feedback (and, in more advanced models - advice and hints).

        Bye.