Re: Evaluation order control between two expressions

Hi Carter, You are right. I had mixed case. In single thread case, I implicitly assumed IO context rather than pure parallel context. Thank you for explanation. Regards, Takenobu 2016-04-30 23:20 GMT+09:00 Carter Schonwald : > > > On Sat, Apr 30, 2016, 10:16 AM

Re: Evaluation order control between two expressions

> José Manuel Calderón Trilla writes: > Is this the reason it wasn't standardized this way to begin with? Miranda's > `seq` is like `pseq` (as was `seq` in other lazy language implementations) > so it's not as if there wasn't precedent. Note that this has been discussed

Re: Evaluation order control between two expressions

On Sat, Apr 30, 2016 at 6:11 AM, Lennart Augustsson wrote: > Order of evaluation can be very important for memory use. So I can imagine > cases where seq would run out of memory, but pseq would not. > That's fair enough. Do you think it's worth attempting to standardize

Re: Evaluation order control between two expressions

On Sat, Apr 30, 2016, 10:16 AM Takenobu Tani wrote: > Hi Prime, > > This is additional information to organize my brain. > > This issue also occurs in single thread. > Especially, when they have side effects. > >seq exp1 exp2 > > Because compiler can always re-order

Re: Evaluation order control between two expressions

Hi Prime, This is additional information to organize my brain. This issue also occurs in single thread. Especially, when they have side effects. seq exp1 exp2 Because compiler can always re-order two expressions in accordance with seq's denotational semantics. Regards, Takenobu

Re: Evaluation order control between two expressions

Order of evaluation can be very important for memory use. So I can imagine cases where seq would run out of memory, but pseq would not. I would argue that pseq is almost always what you want, but seq has a nicer denotational semantics. -- Lennart On Friday, April 29, 2016, José Manuel

Re: Evaluation order control between two expressions

Hi Jose and Cale, Thank you for clear and detailed explanation. short summary: * `seq` used to eliminate/manage space leaks * `pseq` used to specify order of evaluation * `seq` is a bad name, but well established. * If we introduce parallelism to standard, we need `pseq` or some method.

Re: Evaluation order control between two expressions

Well, the value of par x y is identical to that of y, so any expression which you could use to semantically distinguish pseq from seq using par could be rewritten into one which did so without involving par. If the way in which we're telling programs apart involves performance characteristics

Re: Evaluation order control between two expressions

Hello Takenobu, Great question, this is actually a pretty interesting issue! It isn't out of scope at all. The first thing to think about is the following thought experiment: Without the presence of side-effects, how can you tell the difference between a `seq` that conforms to the Haskell

Evaluation order control between two expressions

Dear Community, Apologies if I'm missing context. Does Haskell 2020 specify evaluation order control by `pseq`? We use `pseq` to guarantee the evaluation order between two expressions. But Haskell 2010 did not specify how to control the evaluation order between two expressions. (only specified