World: r3wp

#1653

would we be just using 

forall word word [print word/1] 

all the time ?

woudn't

<arghh>    wouldn't

all the time
?

isn't it more frequent, that you actually do:

my-word: [1 2 3]
forall my-word [do something...]

?

That should properly look this way:

forall my-word [1 2 3] [do something...]

Not using FORALL, I actually do not mind, I just wanted to point 
out what is wrong about it

this is one of the reasons I don't use FORALL very often, but resort 
to repeat i length? <something>

when I have used forall (and its really rare, cause until is much 
better, usually) I never use litteral data directly, its always some 
data which is already setup elsewhere.

I am pretty sure, that *if* FORALL was defined properly from the 
start, everybody would perceive a change to the "two in one argument 
passing method" inappropriate. But, since it is a backward compatibility 
issue, you do not see what is wrong about it. Nevertheless: the WORD 
argument is an independent word, which is used to "define" a local 
in the BODY argument, that is why it actually does not make sense 
to use it as a "series container" on entry

(where it is "nonlocal")

To make it absurd, even REPEAT could be modified to use the "two 
in one argument passing method". Would you find it proper?

...and if not, why?

...and I don't think, that an argument "because that is how REPEAT 
differs from FORALL" makes any sense as an argument

well repeat already uses 2 arguments.

ah sorry... read your statement the wrong way.

In my opinion, different functions are defined not because we like 
to have different functions, but because they do different things 
for us

Assuming (hypothetically), that FORALL did not use the "two in one" 
method, the Graham's example would look as follows:

forall b a/b [print a/b/1]


, which is preferable, since it clearly suggests, that the word 'b 
in the BODY is actually not the same word as in a 'b

Aha, it seems, that I noticed one more strangeness in this. Why actually 
the expression:

forall (in a 'b) [print a/b/1]

prints what it does in R3?

the reason I use 'forall is so I can remove elements of a series 
as I traverse it.

so

forall series [ if series/1 = something [ remove series ]]


which 'foreach doesn't allow because you don't have a reference to 
where you are in the series

use remove-each its MUCH faster.

using your example it becoms.

remove-each [if series/1 = something]

actually... its:
remove-each [series/1 = something]

remove-each is indeed much faster and it's a native.

argh... I'm reallly tire.

Only because Carl made it native!

remove-each item series [item = something]

not just because its native... its in the way it actually manages 
the removal... it only re-creates the series once, when its done.


using other methods, you are tampering with the series at each change, 
and it has to copy the series over and over.

remove-each mistake maxs-mistakes [ true ] ?

Is that the syntax?  :)

yep

Maxim about remove-each, what do you mean by: 
- "it only re-creates the series once, when its done".

what I have been explained is that it makes a new series and only 
copies when remove is false.  then replaces the pointer within the 
series to the new one.

Steeve, removal of one object from a block is an O(n) operation, 
where n is the length of the series. That would make a naive implementation 
O(n ** 2), while REMOVE-EACH is just O(n)

...but, actually, no re-creation of series happens anyway

ah yes.. true.. it just copies over itself.

Ladislav, one question I've always wondered and I'm sure you know.

does CLEAR only set the soft size of a series or does it actually 
truncate the internal buffer of a series?

the former

CLEAR is just O(1)

although,maybe, that in some cases, the GC is able to reassign a 
smaller part of memory to the series, but I doubt it

Are you sure about that ?
I don't tink remove-each create any temporary buffer.

when I compare the footprint of foreach and remove-each, they are 
the same

(which means nothing, because i don't see why foreach need to create 
so much temporary blocks)

Sure about what? I did not tell, that REMOVE-EACH was creating any 
memory buffer

I prefer the actual "two in one" behavior of forall , it allows to 
retrospect where an error happened.

Anton: how?

and to continue from that point

did you check whether your approach is usable in R3?

seems to work
>> a: [ 1 2 3 4]
== [1 2 3 4]

>> forall a [if a/1 = 3 [a/1 / 0] print a]
1 2 3 4
2 3 4
** Math error: attempt to divide by zero
** Where: / if forall
** Near: / 0

>> a
== [3 4]

(i was aiming Maxim)

Aha, then it was an error on my part (the behaviour of FORALL). I 
thought, that its behaviour changed.