World: r3wp

UNIQUE/into, good idea. DEDUPLICATE would use UNIQUE/into internally, 
but I can't think of any other use case. I'm sure others could.

No, that probably wouldn't work because you need the intermediate 
series so you don't have data loss. So, no use case so far.

The /into option wasn't added to many applicable natives, just the 
two that generate the most data in REBOL: REDUCE and COMPOSE. That 
might be a "biggest bang for the buck" thing, or maybe we just haven't 
gotten around to it yet. Or it might be a big hassle to add /into 
to a native, so to get it done you need to justify it with use cases.

Time will tell. Like it or not, REBOL is primarily built around mutating 
functions, except for functions that work on immutable values like 
integers. Most of the non-mutating functions we have are either built 
on their mutating counterparts in mezzanine, or are options of those 
functions. In a language with mutable values, mutating functions 
are the base. Functional-language fans tend to not like this (and 
when we start really implementing task-safe code they can say "I 
told you so!"). However, mutability can have advantages too, mostly 
in memory usage and performance, so it's a tradeoff.

(((( I know you don't agree with me, but I want a VM level way to 
define pure functions (that are guaranteed they can't change anything 
outside itself). 

Big future deal in rebol to me is in runtime code generation to express 
things and *code mobility* and there can't be any real mobility if 
the code I get can "get over the wire" can do anything to my system 
))))

>> reducificate: func [value] [either series? :value [head remove/part 
reduce/into value value tail value] [reduce :value]]

Works for DEDUPLICATE also, no?

uh ????

Modifying REDUCE variant based on REDUCE/INTO, as a general pattern, 
just wondering what the data loss is that BrianH is referring to.

ah! reduce in place.
But what a pain (in the ...)

/INTO is kind of novel and catchy, in terms of some of the optimization 
scenarios it allows for.  Making variants like "/NO-COPY" winds up 
looking like Rebol is doing a bad job of conventions like REDUCE 
vs REDUCE! ... as opposed to playing a whole different game.

It comes to my mind that reduce/into should not behave like inserting 
data but changing them.

Changing data if it's it's at the end of the container will simply 
add them.

But if it's at the head of the container, it will remplace them intead.
Probably more usefull, than the current behavior.

so that 
>> reduce/into data data

would simply do the job we all expecting. To reuse the same block. 
A reduce in place (rest in a peace)

We could only add one behavior for the /into option, and the insert 
behavior was the most basic.

Fork, your method would add the additional series allocation to the 
series itself, temporarily doubling its size (at most). And then 
the reallocated series would stay that size in memory even after 
DEDUPLICATE returns. So overall, worse.

Didn't you say that  UNIQUE has to copy the series anyway?  What's 
the difference?

Would doing the /INTO at the end of the series make it easier for 
the memory allocator to reclaim the space after the remove?

(May have misunderstand what you meant about the algorithm needing 
the original array and a temporary buffer the size of the output, 
as well as the output.)

Oh well, I dunno.  It's too hot here right now to think at all.  
92 indoors in the shade.

{See UNIQUE. This function is not widely used in my apps, just because 
of that. Useless, because when we deals with huge series, we don't 
want to pay the COPY cost.} - while this looks like a reasonable 
argument at the first sight, it actually isn't. The reason why is 
based on the way how UNIQUE is (and has to be) implemented. You cannot 
gain any speed worth that name by allowing an implementation doing 
the "UNIQUE job" in place.

Regarding the above, is there a way to reassign and take exisiting 
references with you?   Or, is this a lack of pointer manipulation?

I guess the argument about existing references then also applies 
to 'unique

Looks like the python FBP is http://www.kamaelia.org/Home.html

ooops ... wrong group

Ladislav/BrianH: so doesn't that imply that the UNIQUE/INTO variant 
would be more useful as a native than UNIQUE/NO-COPY?  (I'm not sure 
how a temporary state of a series of length 2N which has N discarded 
is worse than 2 series of size N in which one of those series is 
discarded.)

these reduce/into b b and unique/into b b make me wonder, whether 
the people suggesting it really find such crazy code useful?

(I never felt like using such things)

Rebol looks crazy to most people regardless.  To my midn, if  Rebol 
has so far avoided a convention like /NO-COPY on these other routines 
in favor of /INTO, then consistent and learnable novelty trumps some 
organic evolution of refinements and wording in the core.

I've never had a need for reduce/into or unique/into. The optimizer 
in my brain says reduce/info could be useful, but the rest of my 
brain thinks the lure of possible optimizations will create internal 
strife with said optimizer. :-) I do have an /into refinment on my 
COLLECT func, and the standard COLLECT does as well, but my goal 
there was for convenience is building up results, not optimization.

but the most crazy is not that reduce/into b b "looks crazy", but 
that it is unneeded, and *very* inefficient, unless implemented using 
copying

It doesn't make sense to reduce/into the same series, but that's 
not the intended purpose. Or am I missing something? Of course, people 
might still do it, thinking they're optimizing. :-\

I guess I just don't care enough about how hard I make the GC work.

Of course, people might still do it, thinking they're optimizing.
 - you nailed it

Anton, I think, it's a "ground rule" in Carl's design of the language, 
that everything entered into the parser are datatypes (or series 
of datatypes). I can't think of anything with semantic meaning, that 
is not a datatype, when we talk REBOL. The language is recognized 
by it's minimalistic syntax. That's why I call it a "ground rule".


I think, it's legal to call REBOL a sequence of datatypes. It's maybe 
more precise than calling it a programming language (also because 
it's so different from traditional programming languages).


And then, yes, he has added newline markers to e.g. blocks. But they 
have no semantic consequence.

Geomol, I thought about it a bit more and realized what you said 
made good sense.

It makes me a bit sad that we haven't found a way to get what I wanted.

But oh yeah, I wrote this experimental function last night.

sforpath: func ["Evaluate a path similar to the builtin path evaluation, 
except number elements SELECT (rather than PICK)."
	path [path!] action [function! block!] /local e v c
][

 v: get path/1 ; The path is assumed to begin with a word, so get 
 its value.

 while [not tail? path: next path][ ; Step through the path to inspect 
 each of its elements.
		c: v ; Store the current value before SELECTing into it.
		e: pick path 1 ; The current element.
		;print [mold :e mold type? :e]
		if get-word? :e [e: get e]
		case [

   number? e [v: select v e] ; SELECT this number element. (Paths normally 
   PICK number elements.)

   word? e [v: select v e] ; SELECT this word element (as paths normally 
   do).
		]
	]
	;?? e ?? v ?? c
	; Process the last element.
	if block? :action [action: func [c e] action]
	action c e
]
; Test
values: [1 [dos [new 0]]]

sforpath 'values/1/dos/new [c/:e: c/:e + 1]  ; <- DideC's INC-COUNTER 
function could be implemented simply using this.

Just to remind, DideC's example had:

values: [

 1 [dos [new 0 modified 0 deleted 0] fic [new 0 modified 0 deleted 
 0]]

 2 [dos [new 0 modified 0 deleted 0] fic [new 0 modified 0 deleted 
 0]]
]

And here's an idea which may make the usage simpler:
Write a function USEPATH, used like this:

	values: [1 [dos [new 0]]]
	p: 'values/1/dos/new

 usepath p [p: p + 1]  ;=== (values/1/dos/new: values/1/dos/new + 
 1)
	values ;== [1 [dos [new 1]]
	
or perhaps, achieving the same result:

	usepath p 'v [v: v + 1]


where v is the value SELECTed by the last element in the path (so 
you can choose a different variable name).
  
or even:

	usepath p 4 'v [v: v + 1]


where 'v is set to refer to the value of the 4th element ('new) in 
the path.

so we can refer to any path element by its number, and so this would 
achieve the same:


 usepath p 3 'v [v/new: v/new + 1]  ;=== (values/1/dos/new: values/1/dos/new 
 + 1)
  
and even crazier:

	usepath p 'root/pid/fs/flag [flag: flag + 1]


where the second path elements (all word!s) reference the values 
actually SELECTed in p,
so these are all equivalent:
	usepath p 'values/pid/fs/flag [fs/dos: flag + 1]
	usepath p 'values/pid/fs/flag [fs/dos: fs/dos + 1]
	usepath p 'values/pid/fs/flag [root/pid/fs/flag: flag + 1]

All good fun.

(Oops, the last three examples should begin:   usepath p 'root/.... 
)

Ladislav, REDUCE/into is used to eliminate a temporary series allocation 
in the common INSERT REDUCE and APPEND REDUCE patterns. It is used 
in mezzanine code, and does in fact reduce memory allocation overhead. 
Hate to break it to you, but REDUCE/into and COMPOSE/into were actually 
worth adding. Sorry.

REDUCE/into and COMPOSE/into cut down 2 copies to 1. They don't eliminate 
copies altogether.

The main reason that UNIQUE isn't used is because it is not very 
useful: It is easier to make sure that the series is unique in the 
first place. The other "set" functions like INTERSECT, DIFFERENCE 
and EXCLUDE are used more often, even though they do the same copies 
as UNIQUE, using the same hashing method.

I suggested REDUCE/into and COMPOSE/into, and found them to be immediately 
useful. I don't know why UNIQUE/into is being suggested, its use 
case.

Henrik had a use case for DEDUPLICATE, though that was when he thought 
he could eliminate the copy, and actually wanted to change UNIQUE 
to be modifying instead. It's not a common enough use case to make 
it into the core functions, but there is a mezzanine for it in the 
CureCode ticket.

REDUCE/into and COMPOSE/into were actually worth adding

 - no problem with that, what I was saying, though, was something 
 else

I specifically had objections against the

    reduce/into b b

expression, which cannot be done efficiently without copying

...neither it is really useful, in my opinion

I definitely agree with that. I can't figure out a use for that code 
pattern, at least at first glance.