On Wednesday, 29 October 2014 at 19:55:14 UTC, H. S. Teoh via
Digitalmars-d wrote:
> On Wed, Oct 29, 2014 at 06:40:50PM +0000, Freddy via Digitalmars-d wrote:
>> On Wednesday, 29 October 2014 at 18:04:30 UTC, John Colvin wrote:
>> >On Wednesday, 29 October 2014 at 17:36:41 UTC, H. S. Teoh via
>> >Digitalmars-d wrote:
> [...]
>> >>I've submitted a PR for byPair before, but it was roadblocked by the
>> >>fact that people demand that it return std.typecons.Tuple, yet we're
>> >>not allowed to import Phobos in druntime. Other than this IMO
>> >>nitpicky issue, the code was already all ready to go many moons ago.
>> >>
>> >>
>> >>T
>> >
>> >Can byPair be implemented in phobos, or does it need to access
>> >private/package stuff in druntime?
>> 
>> I don't see why not,It could be put into std.range and accept a
>> generic associative range(which includes the build-in associative
>> array).
>
> And how would it be implemented in a way that is stable across AA
> implementations?
>
>
> --T
in std.range
----
auto byKeyPair(R)(R r) if(isAssociativeRange!R){
	return zip(r.byKey,r.byValue);
}
----
Although it will not be possible for lazy associative ranges
because they don't allow iteration
b.t.w should I add this to by PR?

On Tuesday, 28 October 2014 at 22:44:32 UTC, Freddy wrote:
> http://wiki.dlang.org/DIP67
> Abstraction over the build-in associative array(one type of range
> for containers and another type for dynamic generators).
> Plese criticize.

Does any one now a better way to implement lazy associative
ranges other than my KeyType and ValueType hack?

On Wed, Oct 29, 2014 at 11:33:53PM +0000, Freddy via Digitalmars-d wrote:
> On Wednesday, 29 October 2014 at 19:55:14 UTC, H. S. Teoh via Digitalmars-d wrote:
[...]
> >And how would it be implemented in a way that is stable across AA implementations?
> >
> >
> >--T
> in std.range
> ----
> auto byKeyPair(R)(R r) if(isAssociativeRange!R){
> 	return zip(r.byKey,r.byValue);
> }
> ----

This is not stable across AA implementations.  There is no guarantee that byKey and byValue will return elements in the same order. The current implementation does, but it's a shaky assumption.

Besides, it wastefully keeps two iterators over the AA, whereas a proper native implementation would only need a single one.

In any case, this is a backwards approach. What we *should* have started with, is an iteration over key/value pairs, with byKey and byValue implemented on top of that, rather than the other way round.

If it weren't for the std.typecons.Tuple issue, we'd already have a proper AA byPair by now. But perhaps there is a way to work around this, if the AA interface can export a "raw" iteration function that can be wrapped in Phobos to produce a range of key/value Tuples... It wouldn't be the prettiest solution, but might be the best we can do right now since we can't import Phobos from druntime.


T

-- 
Windows 95 was a joke, and Windows 98 was the punchline.

On Thursday, 30 October 2014 at 00:10:47 UTC, H. S. Teoh via Digitalmars-d wrote:
> On Wed, Oct 29, 2014 at 11:33:53PM +0000, Freddy via Digitalmars-d wrote:
>> On Wednesday, 29 October 2014 at 19:55:14 UTC, H. S. Teoh via
>> Digitalmars-d wrote:
> [...]
>> >And how would it be implemented in a way that is stable across AA
>> >implementations?
>> >
>> >
>> >--T
>> in std.range
>> ----
>> auto byKeyPair(R)(R r) if(isAssociativeRange!R){
>> 	return zip(r.byKey,r.byValue);
>> }
>> ----
>
> This is not stable across AA implementations.  There is no guarantee
> that byKey and byValue will return elements in the same order. The
> current implementation does, but it's a shaky assumption.

It's already covered by the DIP. Simply, it's one of the requirements of an associative range: "byKey and byValue must be align to the same Pair when iterating." While the compiler can't enforce this, there are many things about ranges which the compiler is unable to check, so we merely expect the implementation to follow the rules.

> Besides, it wastefully keeps two iterators over the AA, whereas a proper
> native implementation would only need a single one.
>
> In any case, this is a backwards approach. What we *should* have started
> with, is an iteration over key/value pairs, with byKey and byValue
> implemented on top of that, rather than the other way round.
>
> If it weren't for the std.typecons.Tuple issue, we'd already have a
> proper AA byPair by now. But perhaps there is a way to work around this,
> if the AA interface can export a "raw" iteration function that can be
> wrapped in Phobos to produce a range of key/value Tuples... It wouldn't
> be the prettiest solution, but might be the best we can do right now
> since we can't import Phobos from druntime.
>
>
> T

On Tuesday, 28 October 2014 at 22:44:32 UTC, Freddy wrote:
> http://wiki.dlang.org/DIP67
> Abstraction over the build-in associative array(one type of range
> for containers and another type for dynamic generators).
> Plese criticize.

Any examples of what this actually accomplishes? Maybe an example of an algorithm that can do something useful with these primitives? A rationale for why these are the chosen primitives?

As the proposed "associative range" isn't consumable like other ranges, this seems more like a specific kind of *container*, not a *range*; indeed the text of the DIP seems to conflate the concepts, but they are separate by necessity.

Note that opIndex and opBinaryRight are already container primitives (see std.container). There's also the additional relevant primitive `removeKey`. Beyond that though, associative containers could need some more fleshing out in the container concept.

As it is, I think this proposal suffers both from lack of substance and confusing terminology.

On Saturday, 1 November 2014 at 00:04:18 UTC, Jakob Ovrum wrote:
> ... opIndex and opBinaryRight are already container ...

Correction: opBinaryRight!"in"

On Saturday, 1 November 2014 at 00:04:18 UTC, Jakob Ovrum wrote:
> On Tuesday, 28 October 2014 at 22:44:32 UTC, Freddy wrote:
>> http://wiki.dlang.org/DIP67
>> Abstraction over the build-in associative array(one type of range
>> for containers and another type for dynamic generators).
>> Plese criticize.
>
> Any examples of what this actually accomplishes? Maybe an example of an algorithm that can do something useful with these primitives? A rationale for why these are the chosen primitives?
>
> As the proposed "associative range" isn't consumable like other ranges, this seems more like a specific kind of *container*, not a *range*; indeed the text of the DIP seems to conflate the concepts, but they are separate by necessity.
>
> Note that opIndex and opBinaryRight are already container primitives (see std.container). There's also the additional relevant primitive `removeKey`. Beyond that though, associative containers could need some more fleshing out in the container concept.
>
> As it is, I think this proposal suffers both from lack of substance and confusing terminology.

The pull request has already been denied. I didn't know about
std.container's definitions.

They can't be consumable, built-in associative arrays overload
foreach(key,value;array) adding input range primitives would
conflict.

On Sat, Nov 01, 2014 at 12:04:16AM +0000, Jakob Ovrum via Digitalmars-d wrote:
> On Tuesday, 28 October 2014 at 22:44:32 UTC, Freddy wrote:
> >http://wiki.dlang.org/DIP67
> >Abstraction over the build-in associative array(one type of range
> >for containers and another type for dynamic generators).
> >Plese criticize.
> 
> Any examples of what this actually accomplishes? Maybe an example of an algorithm that can do something useful with these primitives? A rationale for why these are the chosen primitives?
> 
> As the proposed "associative range" isn't consumable like other ranges, this seems more like a specific kind of *container*, not a *range*; indeed the text of the DIP seems to conflate the concepts, but they are separate by necessity.
> 
> Note that opIndex and opBinaryRight are already container primitives (see std.container). There's also the additional relevant primitive `removeKey`.  Beyond that though, associative containers could need some more fleshing out in the container concept.
> 
> As it is, I think this proposal suffers both from lack of substance and confusing terminology.

I think a better name would be "associative array concept" rather than "associative range".

Basically, this DIP is proposing a set of primitives that can be used to identify some given type as AA-like, so that generic code that expect AA-like objects would be able to work with any type that implements the expected interface. Ostensibly, one could then implement generic algorithms that work with AA-like objects.

It's not a bad idea, really, except perhaps for the name. And the API could use more careful thought to boil it down to the essentials, rather than throwing in everything current AA syntax supports, just because AA syntax supports it. If we can boil down AA's and AA-like types into a small but expressive set of primitive operations, it could turn out to be a very useful abstraction that generic code could use. The current AA syntactic sugar can then be implemented in terms of the minimal primitives, and one could easily build AA-like objects by implementing the primitives, and automatically get all the syntactic sugar "for free" via UFCS and so on.


T

-- 
Why waste time reinventing the wheel, when you could be reinventing the engine? -- Damian Conway