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Coroutine documentation question
by Brian Wood 21 Feb '13

21 Feb '13

I have a question about a sentence on this page: http://www.boost.org/doc/libs/1_53_0/libs/coroutine/doc/html/coroutine/intr… "The principal difference between coroutines and routines is that a coroutine enables explicit suspend and resume their progress via additional operations by preserving local state ..." I'm wondering if it would be accurate/helpful to change that to this: "The principal difference between coroutines and routines is that coroutines enable explicit suspend and resume of their progress via additional operations by preserving local state ..." Shalom Brian Wood Ebenezer Enterprises - so far G-d has helped us. http://webEbenezer.net (651) 251-9384

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Boost.Geometry: Correct use of multi-part polygons
by John Lilley 20 Feb '13

20 Feb '13

Greetings, I am looking for some guidance around the correct creation and use of multi-part polygons. I am a bit confused about when to use each of the following: * Polygon with multiple rings * Vector of polygons * Polygon set * Set/vector of polygons, each potentially containing multiple rings I gather from this example picture: http://geometrylibrary.geodan.nl/03__polygon__example_8cpp-example.html That if one wants holes to be opened as a result of intersection, they need to be rings as opposed to polygon sets or vectors of polygons? An example would be polygon(s) representing an island chain. Some of the islands are atolls and as such have a hole in the middle. What would a representation of this set of islands look like? And, what If I don't know if I have "real" rings (interior) vs just a collection of polygons (like I got this from an external source that doesn't have the same model). If I just throw a pile of points at a polygon and call clean(), will that magic everything up for me? john

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Boost.geometry intersection / difference question
by John Lilley 20 Feb '13

20 Feb '13

What types are the intersection and difference algorithms implemented for? In particular: Can polygons intersect with non-polygons (e.g. point sets to produce clipped point sets, or linestrings to produce clipped linestrings)? Similar question for difference, where polygon is the second input. Thanks John

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Re: [Boost-users] [Atomic] [Tread] Proposal for Synchronized<T>
by Gabriel Bizzotto 20 Feb '13

20 Feb '13

Hi, > I've been working already on a synchronized_value class that is in trunk [1]. I plan to merge it to release branch as soon as I have finished the tests and the documentation. You can see some examples in [2] and [3]. > I've take a look to your class and I think my class provides everything yours provide. Surely your version has been given more thought. > My class allows in addition to lock several synchronized values using the deadlock free lock algorithm as e.g. I did not understand the unique_synchronize part, though. > Please could you compare your class to mine and let me know what do you think? I can't see any flaw right now, but I'm still playing with it. If anything shows up I'll let you know. Thanks !

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Re: [Boost-users] [Atomic] [Tread] Proposal for, Synchronized<T>
by Gabriel Bizzotto 20 Feb '13

20 Feb '13

> I have one that does reader/writer locking. I'll pass it along for comparison along with design notes (it was done partially for teaching), if it's OK to send a zip file to you. > ?John Sure, let's take a look ! You also want to carbon-copy to vicente.botet(a)wanadoo.fr, which is putting the finishing touch on the future boost::synchronized_value.

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Directed cycle detection in a DAG between two nodes
by Amanullah Yasin 20 Feb '13

20 Feb '13

Hi, In Hill Climbing algorithm, before applying an operation "add_edge", "reverse_edge" or "remove_edge", I need to check whether the graph will be a Directed Acyclic Graph (DAG) or not. So there is recursive function but in some cases it goes in infinite loop and gives "stack overflow" error. //======= Function ======= bool myAlgo::remainsADAG(const Node_type& nodeInit, const Node_type& node, const Graph_type& graph) { graph_traits<Graph_type>::adjacency_iterator vi, vi_end; tie(vi, vi_end) = adjacent_vertices(node, graph); for (; vi != vi_end; ++vi) { if ((*vi == nodeInit) || (!remainsADAG(nodeInit, *vi, graph))) return false; } return true; } ============== e.g. for Graph 12->19->20->23 19->24->31->18>19 18->32 To test if there is a directed path between v12 and v32 it goes as: 12->19->20->23 24->31->18>19 *There is an infinite loop{18->19->20->23, 24->31->18}.* ================= Can some one help me or is there any other easy way to find a directed path between two nodes in boost graph? Thanks in advance. YASIN

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[Preprocessor] Generate #include directive with preprocessor
by Adam Badura 20 Feb '13

20 Feb '13

Is it possible to use preprocessor to generate #include directives (or in any other way include the files)? For example if I would have a sequence of strings (being file paths) what to do to include all those files? It is possible at all?

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Sperical / geo coordinates question: crossing anti-meridian
by John Lilley 19 Feb '13

19 Feb '13

I am trying to determine if boost.geometry handles certain cases of spherical coordinates. Suppose you have county outlines of Alaska. The Aleutian Islands chain crosses the anti-meridian, and so contains latitudes that are in the ranges [ 180 - delta ... 180 ] and [ -180, -180 + delta ] where delta is < 20 degrees or so. Simple (2D planar) point-in-polygon and polygon intersection algorithms fall down on these cases due to anti-meridian crossings and flipping between +/- values. Does Boost geometry deal with these issues "correctly"? I put correctly in quotes because there is some real ambiguity in the coordinate system (maybe the polygon really does wrap around the world?), but one could apply a "minimum perimeter" heuristic and normalize the polygons before performing the computation by moving the [ 180 - delta ... 180 ] range over to [ -180 - delta ... -180 ] or vice-versa. Thanks, john

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[Atomic] [Tread] Proposal for, Synchronized<T>
by John M. Dlugosz 19 Feb '13

19 Feb '13

On 2/19/2013 4:02 PM, boost-users-request-at-lists.boost.org |Boost/Allow to home| wrote: > Subject: Re: [Boost-users] [Atomic] [Tread] Proposal for > Synchronized<T> > Message-ID:<5123C32D.9020700(a)wanadoo.fr> > Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" > > Le 19/02/13 17:58, Gabriel Bizzotto a ?crit : >> >Hi ! >> > >> >I've created two simples classes that helped me avoid data races when >> >sharing objects among threads. >> > >> >The idea is to declare objects that need for synchronization as >> >Synchronized<T>, which holds a T and a mutex. To use the T, a Get >> >function has to be called that returns a proxy, which holds a pointer >> >to the T and a scoped lock on the mutex. The proxy defines operator-> >> >and operator* to give access to the T. To have acces to the T, one has >> >to create the proxy. As long as the proxy exists, the mutex associated >> >with the T is locked, effectively preventing use by other threads. I have one that does reader/writer locking. I'll pass it along for comparison along with design notes (it was done partially for teaching), if it's OK to send a zip file to you. —John

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[property_map] constructor of vector_property_map
by Andreas Fabri 19 Feb '13

19 Feb '13

Hello, Why is initial_size in the constructor __________________________________________________________________ vector_property_map(unsigned initial_size, const IndexMap& index = IndexMap()) This constructor version allows to specify maximum index of element that will be stored. Correct number will improve performance, but semantic is always the same. Source: http://www.boost.org/doc/libs/1_53_0/libs/property_map/doc/vector_property_… __________________________________________________________________ not std::size_t, for the simple reason that the std::vector might be bigger. best regards, andreas -- Andreas Fabri, PhD Chief Officer, GeometryFactory Editor, The CGAL Project phone: +33.492.954.912 skype: andreas.fabri

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