World: r3wp

We are doing that is other ways, mostly by paring down the number 
of included-by-default non-native functions to just what the system 
needs, and putting the rest into optional utility modules. (I assume 
you were proposing this for R3, since R2 is in maintenance mode.) 
We are also encouraging this kind of thing to go into community libraries. 
However, there is currently a missing feature in R3 that makes mezzanine 
loop functions rather difficult to write (no RETURN or EXIT passthrough), 
so any added loop functions are *definitely* not going into the system 
until that is resolved.

I was just asking for this just for language purity .... I don't 
care if we never see it or not.

maybe it can be done using some hof instead .. Ladislav's suggestion 
breaks current behaviour

breaks current behaviour
 - much less than any of yours, actually

the thing is... would you want the more generic foreach to automatically 
reduce the second argument? 90% of the time you need reduce there; 
but, then you have foreach reducing or not depending on the first 
argument... and so on. there are a lot of subtle problems; i think 
it's simpler to have a more generic function and keep the simpler 
foreach. (alternatively, but this breaks compatibility, make foreach 
generic and use repeat for the simpler case)

the only problems i have with my nforeach are: i don't like the name, 
and the implementation is more complicated than i'd like it to be 
(though, it should be better in R3).

forneach is better?  :)

foreachn ? lol

I could live with that ... it reads the best

forsome

foursome?

Graham, this group is web public :-)

I was just correcting your spelling!

It's a compound word. The FOR* group omits the hyphens, so FORSOME 
means FOR-SOME.

forevery ?

formulti ?

(as in "multiple", not "multiply")

forfor

forsome is really nice.  I like the pun it goes well with the language 
(and its community) not taking itself too seriously.

the name is actually quite appropriate, since the dialect defines 
what is run or not... which implies that only SOME of the data will 
be operated on.

mine is shorter, and is specialy suited to win further puzzles :-)

traverse [
    all blk-n
    each [a b] blk-a
    skip blk-x 2
    each e blk-e
][
    ;...
]

Hmmm, what if you had a body block for each item in the dialect, 
so the main body is the innermost loop. Interesting to think about 
anyway.

Gregg, the issue becomes, do you want all of them to advance at the 
same time, or nested, and if nested, in which order?

I'd say that nested cases are already well handled by what we have 
so they can be ignored.

So... I guess your idea is not bad at all.

I wonder if there is a way for 'if to not return a value?

I'm looking for a pass thru mode if 'if is false

eg. if I want to avoid the #[none]

>> print rejoin [ "hello " if false [ "world" ]]
hello none

>> print rejoin [ "hello " either true [ "world" ]["" ]]
hello world

>> print rejoin [ "hello " if/only false [ "world" ]]
hello

so something like that ...

This is the construct I saw which I don't like

either true [ tail s ][s ]

which I could  then replace with

 if/only true [ tail ] s

It's less verbose and possibly clearer than using the 'either construct

if/else false [][#[unset!]]

>> only: func [c b][if/else c b [#[unset!]]]
>> only true ["howdy"]
== "howdy"
>> only false ["howdy"]

is this what you need?

Nope .. 

>> print rejoin [ "Hello " only false [ "world" ]]
Hello ?unset?

functions which don't return anything actually return unset!

rejoin is the culprit here.  the only reason your tail s works is 
because you are appending an empty block to a string, which = to 
appending an empty string to a string.

ex:  >> rejoin ["" prin ""]
== "?unset?"

IIRC R3's rejoin now ignores the unset values

I just want if/only to drop a value off the stack if false

only: func [c b][if/else not c b [#[unset!]]]


you can reverse the truth, but you will always return unset!   there 
is no such thing as a function which doesn't return a value in REBOL.

I want to avoid these 'none values ... where you are forced to use 
'either

well, you have to chose between unset! or none!, but R2's rejoin 
collects the unset values and appends them to strings (which is a 
bit dumb).

you can also use compose, which ignores unset! values.

>> reduce compose ["" (prin "")]
== [""]

that's for rejoin ... which is just one example

yes, but other funcs will react differently to unset!... some will 
raise the "expects a value" error, for example, if you return unset! 
from 'IF and try to use it.

well, the value is just one more upstream :)

>> print only true ["rr"]
rr
>> print only false [""]
** Script Error: print is missing its value argument
** Near: print only false [""]