Both of which are not present in VW. Hence, I used the following messages in VW with no name clash:

- #reduce: aReduction "= block + initial value"

- #reduce:init: is similar to #inject:into: but executes an additional completion action

Some obvious ways to avoid a clash in Pharo are:

1) Make #reduce: distinguish between a reduction and a simple block (e.g. by double dispatch)

2) Rename the transducers #reduce: to #injectInto: and adapt #inject:into: to optionally do the completion

3) Find another selector that is not too counter-intuitive

All three approaches have some downsides in my opinion:

1) Though straight forward to implement, both flavors behave quite different, especially with respect to the number of block arguments. The existing one creates a SequenceableCollection and partitions it according to the required number of args. Transducers' #reduce: considers binary blocks as the binary fold case but ternary blocks as fold with indexed elements.

2) This is a real extension of #inject:into: but requires to touch multiple implementations of that message. Something I consider undesirabe.

3) Currently, I cannot think of a good name that is not too far away from what we're familiar with.

Do you have some constructive comments and ideas?

Kind regards,

Steffen

Steffen M��rcker schrieb am Donnerstag, 13. April 2023 17:11:15 (+02:00):

:-D I don't know how compress made onto that site. There is not even an example in the list of language examples where fold/reduce is named compress.

Richard O'Keefe schrieb am Donnerstag, 13. April 2023 16:34:29 (+02:00):

OUCH.  Wikipedia is as reliable as ever, I see.

compress and reduce aren't even close to the same thing.

Since the rank of the result of compression is the same

as the rank of the right operand, and the rank of the

result of reducing is one lower, they are really quite

different.  compress is Fortran's PACK.

https://gcc.gnu.org/onlinedocs/gfortran/PACK.html

On Fri, 14 Apr 2023 at 01:34, Steffen M��rcker <merkste@web.de> wrote:

Hi Richard and Sebastian!

Interesting read. I obviously was not aware of the variety of meanings for fold/reduce. Thanks for pointing this out. Also, in some languages it seems the same name is used for both reductions with and without an initial value. There's even a list on WP on the matter: https://en.wikipedia.org/wiki/Fold_%28higher-order_function%29#In_various_languages

Kind regards,

Steffen

Richard O'Keefe schrieb am Donnerstag, 13. April 2023 13:16:28 (+02:00):

The standard prelude in Haskell does not define anything

called "fold".  It defines fold{l,r}{,1} which can be

applied to any Foldable data (see Data.Foldable).  For

technical reasons having to do with Haskell's

non-strict evaluation, foldl' and foldr' also exist.

But NOT "fold".

https://hackage.haskell.org/package/base-4.18.0.0/docs/Data-Foldable.html#laws

On Thu, 13 Apr 2023 at 21:17, Sebastian Jordan Montano <sebastian.jordan@inria.fr> wrote:

Hello Steffen,

Let's take Kotlin documentation (https://kotlinlang.org/docs/collection-aggregate.html#fold-and-reduce)

> The difference between the two functions is that fold() takes an initial value and uses it as the accumulated value on the first step, whereas the first step of reduce() uses the first and the second elements as operation arguments on the first step.

Naming is not so consistent in all the programming languages, they mix up the names "reduce" and "fold". For example in Haskell "fold" does not take an initial value, so it is like a "reduce" in Kotlin. In Kotlin, Java, Scala and other oo languages "reduce" does not take an initial value while "fold" does. Pharo align with those languages (except that out fold is called #inject:into:)

So for me the Pharo methods #reduce: and #inject:into represent well what they are doing and they are well named.

Cheers,
Sebastian

----- Mail original -----
> De: "Steffen M��rcker" <merkste@web.de>
> ��: "Any question about pharo is welcome" <pharo-users@lists.pharo.org>
> Envoy��: Mercredi 12 Avril 2023 19:03:01
> Objet: [Pharo-users] Collection>>reduce naming

> Hi!
>
> I wonder whether there was a specific reason to name this method #reduce:?
> I would have expected #fold: as this is the more common term for what it
> does. And in fact, even the comment reads "Fold the result of the receiver
> into aBlock." Whereas #reduce: is the common term for what we call with
> #inject:into: .
>
> I am asking not to annoy anyone but out of curiosity. It figured this out
> only by some weird behaviour after porting some code that (re)defines
> #reduce .
>
> Ciao!
> Steffen

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