> From: WF AUTOMACAO <

TakeThisOuTwfRemoveME@spam@AMBIENTE.COM.BR>

> To:

spamBeGonePICLISTEraseMEMITVMA.MIT.EDU
> Subject: Re: FORTH

> Date: Wednesday, October 07, 1998 3:54 PM

>

> Harold Hallikainen wrote:

> >

> > I haven't used FORTH in a while, but am constantly using my HP

> > 15C and HP35 calculators, both of which operate very in a FORTH manner.

> > FORTH and RPN calculators really DO make sense... You give the machine

> > the numbers, then tell it what to do with them. This is also called post

> > fix notation, as opposed to the in fix notation we're more familiar with.

> > Consider a typical calculator's keystrokes...

> >

> > 2 first argument

> > + I can't add anything yet!

> > 3 second argument

> > = ok, I remember, he wanted to add!

> >

> > On an HP (or FORTH), this would be something like

> >

> > 2 first argument, put on stack

> > 3 second argument, put on stack

> > + Replace two arguments on stack with one result

> > of sum, display

> >

> > Also, most calculators that use algebraic notation often use a

> > mix of RPN and algebraic when they have single argument functions:

> >

> > 2 function argument

> > sqrt do the square root of it

> >

> > This mix of in-fix and post-fix on algebraic calculators can make

> > it fun figuring out which to use when (along with hitting the equals key

> > a half dozen times). With RPN, the calculation proceeds the way you

> > would do it by hand (from the inner most parentheses on out).

> >

> > FORTH is an interesting language, though it tends to be write

> > only (no one else can read it). I've seen some neat algorithms that

> > convert algebraic expressions to FORTH, which can then be easily

> > evaluated by a stack oriented machine.

> > Finally, years and years ago I licensed a 6800 Basic interpreter

> > from Microsoft. It's interesting to see how it evaluates an expression.

> > It actually scans the line left to right, interpreting as it goes along.

> > When it sees some sort of two argument operator (like + ), it goes on and

> > evaluates the second argument, which may involve recursive function

> > calls. It's pretty neat. When it finds a function call, it calls the

> > function evaluator, which then looks at the argument and calls the

> > function evaluator again to evaluate the argument to the function. This

> > continues until there is actually some number that is returned, then all

> > the functions return.

> >

> > So... so much for Forth, RPN, and algebra!

> >

> > Harold

> >

> > Harold Hallikainen

> >

spamBeGoneharoldTakeThisOuTspamhallikainen.com
> > Hallikainen & Friends, Inc.

> > See the FCC Rules at

http://hallikainen.com/FccRules and comments filed

> > in LPFM proceeding at

http://hallikainen.com/lpfm
> >

> > ___________________________________________________________________

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>

> If you like Forth, please, do real experiments with Forth 51 at

>

>

http://www.inf.ufsc.br/~jbosco/labvir.htm
>

> Miguel