OpenEuphoria

Re: registration and requests

• Posted by Robert Craig <rds at ATTCANADA.NET> Feb 15, 1999
• 450 views

Gabriel Boehme writes:
> Doesn't the interpreter have
> to check that "while 1" condition each time through the loop?
> Not very speed efficient.

"while 1 do" is optimized away at compile time.
(Actually, any non-zero constant will be optimized.)
No internal code is emitted.
The "end while" will jump unconditionally back to the
first statement in the while loop. No test is ever
performed at run-time.

With Euphoria 2.1 it's even better. Consider:

  while 1 do
        a += 1
        if a > b then
              -- bunch of statements
        end if
  end while

With "branch straightening", when a <= b the internal form
code for the if-statement will jump *directly* back to "a += 1",
without executing the unconditional branch at "end while".

I have to admit that "while 1 do" seems like an awkward
way to introduce an infinite loop (Euphoria is not alone in this.)
However I don't want to introduce a third looping construct. In the very
early days, pre-1.0, I resisted adding the for-loop statement -
everything was done with while-loops up to that time.

John Bown writes (regarding minimalism):
> why were the += / -= operators added ? They
> certainly weren't *needed*.

That's a good point. I resisted adding these assignment operators
for a long time, on the basis of minimalism. Finally a few months
ago I succumbed, after typing statements like:

  galaxy[row][column][otype] = galaxy[row][column][otype] + 1

in many places in Language War.

What would the *ultimate* minimal language look like?

Theoretically the following language, consisting of 4
statements, will let you compute any mathematical
function that you can compute in Euphoria, C++, or any
other programming language. (Note that I/O is not considered,
just computation.)

1.   var = 0
2.   var = var + 1
3.   goto label
4.   loop var times ... end loop

where any statement can have a label, and be the target of a goto.
You can introduce as many vars as you want, without declaring them.

Want to add 3 to x?
     x = x + 1
     x = x + 1
     x = x + 1

Want to assign y to x?
    x = 0
    loop y times
          x = x + 1
    end loop

Want to subtract? multiply? divide? remainder? You can do
them all with loops and adding 1.

Regards,
     Rob Craig
     Rapid Deployment Software
     http://members.aol.com/FilesEu/