Could you explain your example more fully? And what is DROP-DEC?

stevo

On Sun, Feb 7, 2010 at 5:32 PM, Jacob X <[log in to unmask]> wrote:

> Ah, of course. Thank you for explaining it. I had assumed that the meanings
> of the operators remained unchanged (/-->divide the first argument by the
> second); I can see how that might not necessarily be the case.
> However, I begin to wonder whether this, which some have called
> "right-branching English" could also accurately be termed stack English. If
> so, such a variant could make great use of a few stack operators:
> [for clarity, DUP=duplicate the last item in the stack, POP-DEC=pop last
> stack item as declarative.]
>
> Lawyer the man the DUP dog sister my of car with ran-over POP-DEC sister
> behalf of on is-suing DROP-DEC.
>
> Stack English could lead to incredibly intricate constructions involving
> nested sentences such as these; I imagine that it would make organizing
> highly structured texts a much easier task--although reading them would be
> much harder.
>
> On Sun, Feb 7, 2010 at 12:24 PM, Gary Shannon <[log in to unmask]> wrote:
>
> > On Sun, Feb 7, 2010 at 8:57 AM, Jacob X <[log in to unmask]>
> > wrote:
> > > Are you sure that that's the case?
> > > Infix notation:
> > >
> > > 1+2*3-4/5
> > > Which means 6.2.
> > >
> > > Polish notation:
> > >
> > > -+1*23/45
> > > (I don't know how to do push/pop notation for this, but I'll write it
> > out.)
> > > Subtract from the sum of one and the product of two and three the
> > quotient
> > > of four and five. Which seems to mean [(1+(2*3))-(4/5)], or 6.2.
> > >
> > > Reverse Polish notation:
> > >
> > > 123*+45/-
> > > push 1 [1]
> > > push 2 [1, 2]
> > > push 3 [1, 2, 3]
> > > pop 2, 3, multiply, push result [1, 6]
> > > pop 1, 6, add, push result [7]
> > > push 4
> > > push 5
> > > pop 4, 5, divide, push result [7, .8]
> > > pop 7, .8, subtract, push result [6.2]
> > >
> > > I was under the impression that the above was the proper form; but
> these
> > two
> > > expressions are not each others' reverses. What did I do wrong?
> > > (I'm working on a stack-based language  right now, so I would very much
> > like
> > > to know if I'd made an error.)
> >
> > On reconsidering your post, I may be wrong. I don't really know
> > anything much about Polish, so I don't know what the conventions are
> > for argument order. (I have done a lot of FORTH programming, however,
> > so RPN is second nature to me.) Does -xy mean subtract y from x or
> > subtract x from y. I would have taken it to mean "subtract x from y".
> > If that's wrong, then my conclusion is wrong. Both seem reasonable,
> > e.g. a LISP function (subtract 3 1) or a C function Subtract(3,1)
> > would need to explicitly state which argument was to subtracted from
> > the other. Same for division.
> >
> > In general, however, there can often be more than one infix or Reverse
> > Polish version of the same expression:
> >
> > ( 1 + 2 ) * ( 3 * 4 ) = ( 2 + 1 ) * ( 4 * 3 ) = ( 3 * 4 ) * ( 2 + 1 ) =
> ...
> > etc.
> > 12+34** = 21+43** = 34*21+* = ... etc.
> >
> > This is especially true if order of arguments to a function is not
> > understood or explicitly defined
> >
> > --gary
> >
>