Op Fri, 14 Mar 2008 13:39:47 +1100 schreef Ed:
> "Anton Ertl" <anton@[EMAIL PROTECTED]
> wrote in message
news:2008Mar13.111759@[EMAIL PROTECTED]
>> Albert van der Horst <albert@[EMAIL PROTECTED]
> writes:
>>>In article <20080312075319.57514ec7.jethomas5@[EMAIL PROTECTED]
>,
>>>Jonah Thomas <jethomas5@[EMAIL PROTECTED]
> wrote:
>>>>William James <w_a_x_man@[EMAIL PROTECTED]
> wrote:
>>>>> "Ed" <nos...@[EMAIL PROTECTED]
> wrote:
>>>>>
>>>>> > Playing with the algorithm for WITHIN (A.6.2.2440) one gets:
>>>>> >
>>>>> > : BETWEEN ( n1|u1 n2|u2 n3|u3 -- flag ) OVER - -ROT - U< 0= ;
>>>>>
>>>>> Stuff like this leads one to believe that Forth code is
>>>>> unreadable, cryptic, unsharable, and unmaintainable.
>>>>> It's worse than some assembly language I've seen.
>>>>> Forth needs to become a higher-level language.
>>>>
>>>>What are your standards for readability?
>>>>
>>>>I see six commands, and I understand every one of them. No control
>>>>structures. It doesn't get much clearer than that.
>>
>> It does some stack shuffling, it uses the wrap-around properties of
>> computer arithmetic (even a collegue of mine who likes to do much more
>> low-level optimization than is good for the code did not know the
>> trick used by BETWEEN and WITHIN), so there can be clearer words. We
>> can do something about the stack shuffling by using locals:
>>
>>: between { x l u -- f }
>> x l - u l - u<= ;
>>
>> I believe this to be correct. And obviously the factoring here is at
>> least as good as with the stack-shuffling version.
>>
>> Still, if for religious or practical reasons people want to avoid
>> locals, I think the original version also becomes a little more
>> readable by using the return stack:
>>
>>: between ( x l u -- f )
>> over - >r - r> u<= ;
>
> Forth should be coded for performance. I posted the -ROT
> version because it's likely to work out better for most users.
> Most forths have -ROT ; it results in one item less and thus
> hopefully faster; x86 optimizers I tried did a better job on it.
I disagree, using the pair >R and R> would be faster than -ROT, some
primitive implementations could define : ROT SWAP >R SWAP R> ;
But it would make no difference with a native compiler that makes full use
of registers I assume.
--
Coos
CHForth, 16 bit DOS applications
http://home.hccnet.nl/j.j.haak/forth.html
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