Re: [stack] S-K Construction of Dip?

Manfred Von Thun <[email protected]> wrote:
> On 24/2/07 9:45 PM, "Brent L Kerby" <[email protected]> wrote:
> > But, if you can show me a really nice flat programming language, you may be
> > able to change my mind :-)

> Not a NICE flat programming language, but interesting in the present
> context: machine language or assembler.

I've been hammering this in my mind, but I can't get it to work out right.

> Compile into machine language or assembler. Assignments translate into a
> sequence of instructions, but that is of no interest here.  Compound
> statements translate into the sequence of instructions produced by the
> sequence of statements, also of no interest. But interestingly, conditionals
> and loops are  translated into a FLAT sequence of instructions containing
> two new instructions that are not in the source language: conditional and
> unconditional JUMP instructions. We also have the notion of a program
> counter, which is simply incremented by most instructions. Only the JUMP
> instructions change the program counter explicitly.

The problem is that machine language/assembler uses explicit offsets
to express jumps and branches, and those destroy referential
transparency. In effect, you can't split a valid program into two
arbitrary parts and have the two parts still be valid -- if you cut in
the middle of a branch, the branch will then lead off into nowhere.

> A possible technique for flattening a concatenative language? Probably
> yes. But the flattened version will not be pretty.

Pretty is not yet my concern. But this isn't flat.

But I do suspect there's something to this. I just have to figure out
what I'm missing.

>   - Manfred

-Billy