On Wed, Feb 25, 2009 at 7:39 PM, Thorsten Ottosen <thorsten.ottosen@dezide.com> wrote:
Giovanni Piero Deretta skrev:
On Wed, Feb 25, 2009 at 7:04 PM, Thorsten Ottosen <thorsten.ottosen@dezide.com> wrote:
What about something like
total = r | filter(f) | map(m) -> accumulate(zero, a);
how would you make this work (leaving the framework extensible to new algorithm)? Maybe you meant ->*.
or
total = r | filter(f) | map(m) >> accumulate(zero, a);
I sort of like the >> syntax (btw, I think that there are functional languages that use the same syntax for function chaining), but I do not see the necessity of distinguishing between '|' and '>>'. Just use one.
Well, since there is a semantical difference, and a large one, I'm leaning towards that we should use two operators.
Still not convinced. You might have a case if the last algorithm in the above chain were a mutating one, like sort, but I used accumulate which is a pure function, like map and filter. I do not see much of a difference. Similarly for_each, which while not a pure fuction, it is often used in a way that doesn't mutate its arguments. So no, I do not think that there is a large difference between adaptors and algorithms. I only see the usual difference between mutating and non mutating algorithms.
Especially is we will have both adaptor::transform and transform as an algorithm.
Again, I think that the mutating and not mutating algorithm should have different names.
?
The is a problem when we just want to apply several algorithms:
boost::erase( cont, boost::unique( boost::sort(cont) ) );
I woudn't put many inplace algorithm in the same expression nor encourage users to do it. The unique->erase idiom is common, on the other hand sort has little reason being in that expression.
Unique won't work properly if you don'e have a sorted sequence, AFAIR
IIRC there is no requirement for the range to be sorted: unique will just remove all but one elements on a run of equivalent elements. But I agree that's not how it is often used. Anyways, probably that's more of a case for encapsulating the sort/unique/erase sequence in a single algorithm. -- gpd