Re: [stack] Code Transformation Problem (possibly monadic?)

On Dec 10, 2007 2:22 PM, William Tanksley, Jr <[email protected]> wrote:
> Christopher Diggins <[email protected]> wrote:
>  > Given the following sequence of instruction:
>  > a b m [c m d e] f g
>  > I want an automated transform (no matter how inefficient, it just has
>  > to be algorithmic) to rewrite the code so that each instruction
>  > applies to the stack below the top value, except for "m".
>
>  > The naive transformation would be:
>  > [a b m [c m d e] f g] dip
>  > However, we have a problem because the "m" instruction can't see the
>  > top of the stack.
>
>  Okay, I see what you want, kinda.
>
>
>  > The next obvious transformation (which doesn't work) would then be:
>  > [a] dip [b] dip m [[[c] dip m [d] dip [e] dip]] dip [f] dip [g] dip
>
>  The problem here -- or one of the problems here -- is that you're
>  diving into the quotation as though it were transparent. It's not;

I'm allowed though because it is a source code transformation that I want.

>  it's a unit. So the "next obvious transformation" should actually be:
>
>  [a] dip [b] dip m [[c m d e]] dip [f] dip [g] dip

This is not what I want.

>  At this point, though, I have to stop and wonder what your problem
>  really means. When you say "each function applies to the stack below
>  the top value", do you mean what I just wrote, or do you mean that the
>  ENTIRE SEQUENCE ignores the value which was on the top just prior to
>  execution of the sequence, except for 'm', which for some reason sees
>  the value but doesn't destroy it (so that the next 'm' can also see
>  it)? That's a very complex semantics. Why do it?

Rewrite code to pass values without changing the order of operations.

>  However, here's a transform which appears to meet your request.
>
>  [a] dip [b] dip dup [m] dip [[c m d e]] dip [f] dip [g] dip

"c", "d", and "e" would take the top of the stack as an unintentional argument.

>  Note that each occurence of m is replaced by 'dup [m] dip', while all
>  the other words 'x' are replaced by '[x] dip'.
>
>  I still don't see why to do this, so I don't know if I'm violating
>  something by failing to break into the nested quotation.

Yeah, unfortunately. Thanks for giving it a shot though.

>  > Christopher
>
>  -Wm

- Christopher