Re: [boost] Re: Date iterators in Boost Date-Time
On Mon, 18 Aug 2003 16:28:22 -0400, Beman Dawes wrote > FWIW, I'm both a native-speaker and familiar with convex hulls. > Regardless, "span" sounds better to me for use in the context of a > Date-Time library. Ok, span it is. Updates checked into CVS Jeff ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
RE: [boost] Re: Date iterators in Boost Date-Time
Thanks - it does now make sense, but since (mercifully!) time is only 1-dimensional, I find the span suggestion more intuitive. Paul PS This explanation could usefully be added to the interval library documentation. I was puzzled why the word 'hull' was used. | -Original Message- | From: [EMAIL PROTECTED] | [mailto:[EMAIL PROTECTED] Behalf Of Guillaume Melquiond | Sent: Monday, August 18, 2003 8:36 AM | To: Boost mailing list | Subject: RE: [boost] Re: Date iterators in Boost Date-Time | | | En réponse à "Paul A. Bristow" <[EMAIL PROTECTED]>: | | > But as Michael Caine said "Not a lot of people know that" - so I trust | > you will explain what it does too for the benefit of us mere | non-mathematical | > mortals! | > | > Paul | | I'm not sure to understand. Do you want me to explain what a convex hull is or | to explain what the function of the date-time library is supposed to do? I | suppose it's the first, since the second is what started this subthread. | | A connected set is a set for which each couple of points are | connected by a path | itself included in the set (all the points are reachable from all the | points). A | convex set is a connected set with linear paths (all the points can be reached | from all the other points by following a segment). The convex hull of a set is | the smallest convex superset of it. For example, given three points in the | plane, the convex hull is the filled triangle defined by these points. | | In the case of a 1-dimension space, connected and convex set are equals: they | are segments (or half-line or line or empty). Date manipulated by the | date-time | library are in a 1-dimension space (the real line) and periods are segments | (non-empty bounded convex sets). So when you have two periods, the smallest | period enclosing these two is also the convex hull of them. Hence the name I | suggested. | | I hope it makes sense. | | Regards, | | Guillaume | ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
Beman Dawes <[EMAIL PROTECTED]> writes: | At 03:18 PM 8/18/2003, Victor A. Wagner, Jr. wrote: | | >At Monday 2003-08-18 11:39, you wrote: | >>"Victor A. Wagner, Jr." <[EMAIL PROTECTED]> writes: | >> | >>| how about "span" ? | >> | >>when read as "the period of time spanned by these two", I can make | >>sense of it, even not as a mathematician :-) | >> | >>Well, I don't know how it sounds to native speakers. | | FWIW, I'm both a native-speaker and familiar with convex | hulls. Regardless, "span" sounds better to me for use in the context | of a Date-Time library. Great! We're in violent agreement. -- Gaby ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
At 03:18 PM 8/18/2003, Victor A. Wagner, Jr. wrote: >At Monday 2003-08-18 11:39, you wrote: >>"Victor A. Wagner, Jr." <[EMAIL PROTECTED]> writes: >> >>| how about "span" ? >> >>when read as "the period of time spanned by these two", I can make >>sense of it, even not as a mathematician :-) >> >>Well, I don't know how it sounds to native speakers. FWIW, I'm both a native-speaker and familiar with convex hulls. Regardless, "span" sounds better to me for use in the context of a Date-Time library. --Beman ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
On the other hand, "hull" encompasses the idea of a "periodic hull" that can be used for periodic intervals of time... On Monday, August 18, 2003, at 02:39 PM, John Fuller wrote: It also has the advantage of being similar to the use of "makespan" as the time from the start time of the first job to the completion time of the last job in job scheduling problems. On Monday, August 18, 2003, at 02:18 PM, Victor A. Wagner, Jr. wrote: I suggested it because we write software for people who run multiple experiments with "rest periods" between the data collection sessions. They seem to use the word span to specify the approximate duration of the series of tests. "These experiments were conducted over a span of 3 weeks." Then again, Americans are notorious for abuse of the language, but around University of Arizona's Neural Systems, Memory & Aging Lab it would certainly be understood. At Monday 2003-08-18 11:39, you wrote: "Victor A. Wagner, Jr." <[EMAIL PROTECTED]> writes: | how about "span" ? when read as "the period of time spanned by these two", I can make sense of it, even not as a mathematician :-) Well, I don't know how it sounds to native speakers. -- Gaby ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost Victor A. Wagner Jr. http://rudbek.com The five most dangerous words in the English language: "There oughta be a law" ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
It also has the advantage of being similar to the use of "makespan" as the time from the start time of the first job to the completion time of the last job in job scheduling problems. On Monday, August 18, 2003, at 02:18 PM, Victor A. Wagner, Jr. wrote: I suggested it because we write software for people who run multiple experiments with "rest periods" between the data collection sessions. They seem to use the word span to specify the approximate duration of the series of tests. "These experiments were conducted over a span of 3 weeks." Then again, Americans are notorious for abuse of the language, but around University of Arizona's Neural Systems, Memory & Aging Lab it would certainly be understood. At Monday 2003-08-18 11:39, you wrote: "Victor A. Wagner, Jr." <[EMAIL PROTECTED]> writes: | how about "span" ? when read as "the period of time spanned by these two", I can make sense of it, even not as a mathematician :-) Well, I don't know how it sounds to native speakers. -- Gaby ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost Victor A. Wagner Jr. http://rudbek.com The five most dangerous words in the English language: "There oughta be a law" ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
I suggested it because we write software for people who run multiple experiments with "rest periods" between the data collection sessions. They seem to use the word span to specify the approximate duration of the series of tests. "These experiments were conducted over a span of 3 weeks." Then again, Americans are notorious for abuse of the language, but around University of Arizona's Neural Systems, Memory & Aging Lab it would certainly be understood. At Monday 2003-08-18 11:39, you wrote: "Victor A. Wagner, Jr." <[EMAIL PROTECTED]> writes: | how about "span" ? when read as "the period of time spanned by these two", I can make sense of it, even not as a mathematician :-) Well, I don't know how it sounds to native speakers. -- Gaby ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost Victor A. Wagner Jr. http://rudbek.com The five most dangerous words in the English language: "There oughta be a law" ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
"Victor A. Wagner, Jr." <[EMAIL PROTECTED]> writes: | how about "span" ? when read as "the period of time spanned by these two", I can make sense of it, even not as a mathematician :-) Well, I don't know how it sounds to native speakers. -- Gaby ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
how about "span" ? At Monday 2003-08-18 02:43, you wrote: Guillaume Melquiond <[EMAIL PROTECTED]> writes: | In the case of a 1-dimension space, connected and convex set are | equals: they are segments (or half-line or line or empty). Date | manipulated by the date-time library are in a 1-dimension space (the | real line) and periods are segments (non-empty bounded convex | sets). So when you have two periods, the smallest period enclosing | these two is also the convex hull of them. Hence the name I suggested. that is fine for some mathematically oriented mind. However, it is a terrible name. -- Gaby ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost Victor A. Wagner Jr. http://rudbek.com The five most dangerous words in the English language: "There oughta be a law" ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
"Jeff Garland" <[EMAIL PROTECTED]> writes: | On 18 Aug 2003 11:43:26 +0200, Gabriel Dos Reis wrote | > Guillaume Melquiond <[EMAIL PROTECTED]> writes: | > | > | In the case of a 1-dimension space, connected and convex set are | > | equals: they are segments (or half-line or line or empty). Date | > | manipulated by the date-time library are in a 1-dimension space | > (the | real line) and periods are segments (non-empty bounded convex | > | sets). So when you have two periods, the smallest period enclosing | > | these two is also the convex hull of them. Hence the name I suggested. | > | > that is fine for some mathematically oriented mind. However, it is a | > terrible name. | | | Here is how I explain it: Oh, I'm myself a Geometer and I understand the terminology and have a good mental picture of it. But if we were after accurate, descriptive and mathematically oriented terminology, I can throw "geodesic arc" for this particular case (and I may even attempt to justify it from General Relativity point of view :-). The point of my previous remark is that it is one thing to justify a a name from a mathematically oriented point of view, it is another to name a software entity designed for brother audience; and even for a mathematical audiance I doubt it would be a good name in the case under consideration. -- Gaby ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
On 18 Aug 2003 11:43:26 +0200, Gabriel Dos Reis wrote > Guillaume Melquiond <[EMAIL PROTECTED]> writes: > > | In the case of a 1-dimension space, connected and convex set are > | equals: they are segments (or half-line or line or empty). Date > | manipulated by the date-time library are in a 1-dimension space > (the | real line) and periods are segments (non-empty bounded convex > | sets). So when you have two periods, the smallest period enclosing > | these two is also the convex hull of them. Hence the name I suggested. > > that is fine for some mathematically oriented mind. However, it is a > terrible name. Here is how I explain it: Combines two periods and any gap between them such that start = min(p1.start, p2.start) end = max(p1.end , p2.end) Or graphically: [---p1---) [---p2---) result: [---p3--) Jeff ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
On Mon, 18 Aug 2003 06:34:35 -0500, John Fuller wrote
> HL7 v3, a health care application layer specification, uses the term
> with time intervals as
> an operation on a totally ordered set that produces the smallest
> interval that is a superset.
> For example, hull({[1,5], [7,10]}) == [1,10]
> The unabridged specification part II available on Dr. Schadow's page
> http://aurora.regenstrief.org/v3dt/
> gives nice examples.
John -
Thanks for this pointer. I've changed the name to hull in CVS so it will be
nice to have some examples. This is one of the more interesting public
specifications of time related concepts I've seen -- matches up quite well
with many of the concepts in the library :-)
Jeff
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Re: [boost] Re: Date iterators in Boost Date-Time
HL7 v3, a health care application layer specification, uses the term with time intervals as
an operation on a totally ordered set that produces the smallest interval that is a superset.
For example, hull({[1,5], [7,10]}) == [1,10]
The unabridged specification part II available on Dr. Schadow's page http://aurora.regenstrief.org/v3dt/
gives nice examples.
On Sunday, August 17, 2003, at 05:13 PM, Paul A. Bristow wrote:
But as Michael Caine said "Not a lot of people know that" - so I trust you will
explain what it does too for the benefit of us mere non-mathematical mortals!
Paul
| -Original Message-
| From: [EMAIL PROTECTED]
| [mailto:[EMAIL PROTECTED] Behalf Of [EMAIL PROTECTED]
| Sent: Sunday, August 17, 2003 7:11 AM
| To: Boost mailing list
| Subject: Re: [boost] Re: Date iterators in Boost Date-Time
|
|
| En réponse à Jeff Garland <[EMAIL PROTECTED]>:
|
| I just wanted to mention that the interval library names this
| operation "hull".
| It is a mathematically defined term since the operation is indeed a
| convex hull.
|
| Just my two eurocents,
|
| Guillaume
|
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Re: [boost] Re: Date iterators in Boost Date-Time
Guillaume Melquiond <[EMAIL PROTECTED]> writes: | In the case of a 1-dimension space, connected and convex set are | equals: they are segments (or half-line or line or empty). Date | manipulated by the date-time library are in a 1-dimension space (the | real line) and periods are segments (non-empty bounded convex | sets). So when you have two periods, the smallest period enclosing | these two is also the convex hull of them. Hence the name I suggested. that is fine for some mathematically oriented mind. However, it is a terrible name. -- Gaby ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
RE: [boost] Re: Date iterators in Boost Date-Time
En réponse à "Paul A. Bristow" <[EMAIL PROTECTED]>: > But as Michael Caine said "Not a lot of people know that" - so I trust > you will explain what it does too for the benefit of us mere non-mathematical > mortals! > > Paul I'm not sure to understand. Do you want me to explain what a convex hull is or to explain what the function of the date-time library is supposed to do? I suppose it's the first, since the second is what started this subthread. A connected set is a set for which each couple of points are connected by a path itself included in the set (all the points are reachable from all the points). A convex set is a connected set with linear paths (all the points can be reached from all the other points by following a segment). The convex hull of a set is the smallest convex superset of it. For example, given three points in the plane, the convex hull is the filled triangle defined by these points. In the case of a 1-dimension space, connected and convex set are equals: they are segments (or half-line or line or empty). Date manipulated by the date-time library are in a 1-dimension space (the real line) and periods are segments (non-empty bounded convex sets). So when you have two periods, the smallest period enclosing these two is also the convex hull of them. Hence the name I suggested. I hope it makes sense. Regards, Guillaume ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
RE: [boost] Re: Date iterators in Boost Date-Time
But as Michael Caine said "Not a lot of people know that" - so I trust you will explain what it does too for the benefit of us mere non-mathematical mortals! Paul | -Original Message- | From: [EMAIL PROTECTED] | [mailto:[EMAIL PROTECTED] Behalf Of [EMAIL PROTECTED] | Sent: Sunday, August 17, 2003 7:11 AM | To: Boost mailing list | Subject: Re: [boost] Re: Date iterators in Boost Date-Time | | | En réponse à Jeff Garland <[EMAIL PROTECTED]>: | | I just wanted to mention that the interval library names this | operation "hull". | It is a mathematically defined term since the operation is indeed a | convex hull. | | Just my two eurocents, | | Guillaume | ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
On Sun, 17 Aug 2003 08:11:14 +0200 (CEST), gmelquio wrote > I just wanted to mention that the interval library names this > operation "hull". It is a mathematically defined term since the > operation is indeed a convex hull. > > Just my two eurocents, > > Guillaume Thanks, I like it. Precise and short. Hate to admit I didn't know that, but whatever, my editor is firing up now :-) Jeff ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
En réponse à Jeff Garland <[EMAIL PROTECTED]>: > On Sat, 16 Aug 2003 23:31:05 -0400, Jeremy B. Maitin-Shepard wrote > > > > Yes, of course, it is not really a union either. I think > > > merge_inclusive is fine. > > > > How about "maximize" or "maximize_duration" or just "max" or > > "max_duration"? > > Thx for the ideas, but... > > I'm leary of these b/c this is an operation on a period not a duration. > max is way too overloaded; and still not sure it explains the operation. I > still haven't heard a name that really strikes me as really good. > > Jeff I just wanted to mention that the interval library names this operation "hull". It is a mathematically defined term since the operation is indeed a convex hull. Just my two eurocents, Guillaume ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
On Sat, 16 Aug 2003 23:31:05 -0400, Jeremy B. Maitin-Shepard wrote > > Yes, of course, it is not really a union either. I think > > merge_inclusive is fine. > > How about "maximize" or "maximize_duration" or just "max" or > "max_duration"? Thx for the ideas, but... I'm leary of these b/c this is an operation on a period not a duration. max is way too overloaded; and still not sure it explains the operation. I still haven't heard a name that really strikes me as really good. Jeff ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
[boost] Re: Date iterators in Boost Date-Time
On Sat, 16 Aug 2003 12:28:57 +1000 "Chris Trengove" <[EMAIL PROTECTED]> wrote: > "Jeff Garland" <[EMAIL PROTECTED]> wrote in message > news:[EMAIL PROTECTED] > > I don't think the it is technically a union because the result draws > > in points in the time period that aren't part of either of the > > initial > periods. > > Anyway I wrote the code as merge_inclusive so unless you have a > > major objection I'll leave it that way pending a better idea... > > Yes, of course, it is not really a union either. I think > merge_inclusive is fine. How about "maximize" or "maximize_duration" or just "max" or "max_duration"? -- Jeremy B. Maitin-Shepard [EMAIL PROTECTED] ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
Re: [boost] Re: Date iterators in Boost Date-Time
On Fri, 15 Aug 2003 12:36:52 +1000, Chris Trengove wrote > I think the big issue in using random access iterators is whether > you want to support the difference concept. It is relatively > straightforward to implement, say > > year_iterator i(date(2003,1,1)); > year_iterator j(date(2005,1,1)); > cout << j - i;// prints "2" Right. > but how do you handle the case when the dates are not neatly aligned > on the places where the iterator would normally put them? Ok. But I suspect day_iterators and time_iterators would probably be ok. month_iterators would be a problem... > Your period concept supports the merge (ie. union) function, which returns > an empty period if there is no intersection. I also have a need for a > function returning the actual [earliest,latest) of the two periods, > regardless of whether they intersect. Obviously, this is trival to > write, but it would be nice if the concept was included in the library. Sure, can do. What would you call it: merge_inclusive, earliest_latest, rename merge to union and call it merge, something else? Jeff ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
[boost] Re: Date iterators in Boost Date-Time
"Jeff Garland" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > Another user has submitted a change to me, that hasn't made it into > the library, that performs the equivalent by modifying adjust_functors.hpp. > Looking back on the history of the number of requests on this it looks like > it should be a priority to officially support this option. Or perhaps, even > better, to step up and support bi-directional or random access iterators. I think the big issue in using random access iterators is whether you want to support the difference concept. It is relatively straightforward to implement, say year_iterator i(date(2003,1,1)); year_iterator j(date(2005,1,1)); cout << j - i;// prints "2" but how do you handle the case when the dates are not neatly aligned on the places where the iterator would normally put them? I have one more question/suggestion. Your period concept supports the merge (ie. union) function, which returns an empty period if there is no intersection. I also have a need for a function returning the actual [earliest,latest) of the two periods, regardless of whether they intersect. Obviously, this is trival to write, but it would be nice if the concept was included in the library. Chris ___ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
