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  • docs/examples on libxml2 type system?

    - by Wang
    I'm reading through the libxml2 API and examples on xmlsoft.com and having some real difficulty wrapping my head around the type system. For example, the _xmlAttribute struct has an xmlChar* field called name. This obviously refers to the name of the attribute (e.g., "bar" for the struct tied to the element <foo bar='baz' />). The _xmlAttribute struct also has a field called value, which I would expect to be "baz", except the type is xmlNodePtr. Um, what? I guess I could write up some test code and examine the memory in gdb, but there has to be an easier way. Has anyone written up examples of the data structures generated by a libxml2 parser? I'm looking for an English prose text, not generated documentation, that will walk me through the various types and the values they take when parsing some example bit of XML. Bonus points if it presents only the subset of libxml2 needed to read and write a config file---no namespaces or XPath or even modifying an existing document, just parse some XML, access the data, and then write it out again.

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  • Oracle XMLDB's XMLCAST and XMLQUERY incompatible with iBatis?

    - by tthong
    I've been trying to select a list of values from XMLs stored in an XMLType column but I keep getting the errors which are listed at the tail end of this post. The select id is getXMLFragment , and the relevant subset of the sqlmap.xml is as follows: <select id="getXMLFragment" resultClass="list"> SELECT XMLCAST(XMLQUERY('$CUSTOMER/CUSTOMER/DETAILS/ CUST_NAME/text()' PASSING CUSTOMER AS "CUSTOMER" RETURNING CONTENT) AS VARCHAR2(20)) AS customers FROM SHOP.CLIENT_INFO </select> (CUSTOMER is an XMLType column in CLIENT_INFO) and I call the statement using List<String> custNames= (List<String>) sqlMap.queryForList("getXMLFragment"); I am using ibatis-2.3.4.726.jar. Is it because iBatis does not recognise XMLDB queries and hence, tokenizes the string wrongly? On a sidenote, I have implemented XMLTypeCallback.java to handle XMLType insertions successfully, and I think it will work should I wish to retrieve the entire XML. However, in this case, I need to extract only individual values due to requirements. A workaround would be greatly appreciated. Thanks in advance. The exceptions generated are listed below: --- The error occurred in sqlMap.xml. --- The error occurred while preparing the mapped statement for execution. --- Check the getXMLFragment. --- Check the SQL statement. --- Cause: java.util.NoSuchElementException at com.ibatis.sqlmap.engine.mapping.statement.MappedStatement.executeQueryWithCallback(MappedStatement.java: 204) at com.ibatis.sqlmap.engine.mapping.statement.MappedStatement.executeQueryForList(MappedStatement.java: 139) at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForList(SqlMapExecutorDelegate.java: 567) at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.queryForList(SqlMapExecutorDelegate.java: 541) at com.ibatis.sqlmap.engine.impl.SqlMapSessionImpl.queryForList(SqlMapSessionImpl.java: 118) at com.ibatis.sqlmap.engine.impl.SqlMapSessionImpl.queryForList(SqlMapSessionImpl.java: 122) at com.ibatis.sqlmap.engine.impl.SqlMapClientImpl.queryForList(SqlMapClientImpl.java: 98) at Main.main(Main.java:60) Caused by: java.util.NoSuchElementException at java.util.StringTokenizer.nextToken(StringTokenizer.java:332) at com.ibatis.sqlmap.engine.mapping.sql.simple.SimpleDynamicSql.processDynamicElements(SimpleDynamicSql.java: 90) at com.ibatis.sqlmap.engine.mapping.sql.simple.SimpleDynamicSql.getSql(SimpleDynamicSql.java: 45) at com.ibatis.sqlmap.engine.mapping.statement.MappedStatement.executeQueryWithCallback(MappedStatement.java: 184) ... 7 more

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  • Help with JPQL query

    - by Robert
    I have to query a Message that is in a provided list of Groups and has not been Deactivated by the current user. Here is some pseudo code to illustrate the properties and entities: class Message { private int messageId; private String messageText; } class Group { private String groupId; private int messageId; } class Deactivated { private String userId; private int messageId; } Here is an idea of what I need to query for, it's the last AND clause that I don't know how to do (I made up the compound NOT IN expression). Filtering the deactivated messages by userId can result in multiple messageIds, how can I check if that subset of rows does not contain the messageId? SELECT msg FROM Message msg, Group group, Deactivated unactive WHERE group.messageId = msg.messageId AND (group.groupId = 'groupA' OR group.groupId = 'groupB' OR ...) AND ('someUserId', msg.messageId) NOT IN (unactive.userId, unactive.messageId) I don't know the number of groupIds ahead of time -- I receive them as a Collection<String> so I'll need to traverse them and add them to the JPQL dynamically.

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  • help in the Donalds B. Johnson's algorithm, i cannot understand the pseudo code (PART II)

    - by Pitelk
    Hi all , i cannot understand a certain part of the paper published by Donald Johnson about finding cycles (Circuits) in a graph. More specific i cannot understand what is the matrix Ak which is mentioned in the following line of the pseudo code : Ak:=adjacency structure of strong component K with least vertex in subgraph of G induced by {s,s+1,....n}; to make things worse some lines after is mentins " for i in Vk do " without declaring what the Vk is... As far i have understand we have the following: 1) in general, a strong component is a sub-graph of a graph, in which for every node of this sub-graph there is a path to any node of the sub-graph (in other words you can access any node of the sub-graph from any other node of the sub-graph) 2) a sub-graph induced by a list of nodes is a graph containing all these nodes plus all the edges connecting these nodes. in paper the mathematical definition is " F is a subgraph of G induced by W if W is subset of V and F = (W,{u,y)|u,y in W and (u,y) in E)}) where u,y are edges , E is the set of all the edges in the graph, W is a set of nodes. 3)in the code implementation the nodes are named by integer numbers 1 ... n. 4) I suspect that the Vk is the set of nodes of the strong component K. now to the question. Lets say we have a graph G= (V,E) with V = {1,2,3,4,5,6,7,8,9} which it can be divided into 3 strong components the SC1 = {1,4,7,8} SC2= {2,3,9} SC3 = {5,6} (and their edges) Can anybody give me an example for s =1, s= 2, s= 5 what if going to be the Vk and Ak according to the code? The pseudo code is in my previous question in http://stackoverflow.com/questions/2908575/help-in-the-donalds-b-johnsons-algorithm-i-cannot-understand-the-pseudo-code and the paper can be found at http://stackoverflow.com/questions/2908575/help-in-the-donalds-b-johnsons-algorithm-i-cannot-understand-the-pseudo-code thank you in advance

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  • Large scale storage for incrementally-appended documents?

    - by Ben Dilts
    I need to store hundreds of thousands (right now, potentially many millions) of documents that start out empty and are appended to frequently, but never updated otherwise or deleted. These documents are not interrelated in any way, and just need to be accessed by some unique ID. Read accesses are some subset of the document, which almost always starts midway through at some indexed location (e.g. "document #4324319, save #53 to the end"). These documents start very small, at several KB. They typically reach a final size around 500KB, but many reach 10MB or more. I'm currently using MySQL (InnoDB) to store these documents. Each of the incremental saves is just dumped into one big table with the document ID it belongs to, so reading part of a document looks like "select * from saves where document_id=14 and save_id 53 order by save_id", then manually concatenating it all together in code. Ideally, I'd like the storage solution to be easily horizontally scalable, with redundancy across servers (e.g. each document stored on at least 3 nodes) with easy recovery of crashed servers. I've looked at CouchDB and MongoDB as possible replacements for MySQL, but I'm not sure that either of them make a whole lot of sense for this particular application, though I'm open to being convinced. Any input on a good storage solution?

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  • NAudio Mp3 Playback in Console

    - by Kurru
    Hi I'm trying to make a helper dll that will simplify the NAudio framework into a subset of functions I'm likely to need but I've hit a stumbling block right off the bat. I'm trying to use the following code to play an mp3 but I'm not hearing anything at all. Any help would be appreciated! static WaveOut waveout; static WaveStream playback; static System.Threading.ManualResetEvent wait = new System.Threading.ManualResetEvent(false); static void Main(string[] args) { System.Threading.Thread t = new System.Threading.Thread(new System.Threading.ThreadStart(PlaySong)); t.Start(); wait.WaitOne(); System.Threading.Thread.Sleep(2 * 1000); waveout.Stop(); waveout.Dispose(); playback.Dispose(); } static void PlaySong() { waveout = new WaveOut(); playback = OpenMp3Stream(@"songname.mp3"); waveout.Init(playback); waveout.Play(); Console.WriteLine("Started"); wait.Set(); } private static WaveChannel32 OpenMp3Stream(string fileName) { WaveChannel32 inputStream; WaveStream mp3Reader = new Mp3FileReader(fileName); WaveStream pcmStream = WaveFormatConversionStream.CreatePcmStream(mp3Reader); WaveStream blockAlignedStream = new BlockAlignReductionStream(pcmStream); inputStream = new WaveChannel32(blockAlignedStream); return inputStream; }

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  • Broken tables in RichTextBox control (word wrap)

    - by Ben Robbins
    We are having problems with the Windows.Forms.RichTextBox control in Visual Studio 2008. We are trying to display text supplied as an RTF file by a 3rd party in a windows forms application (.NET 3.5). In this RTF text file there are tables, which contain text that spans multiple lines. The RTF file displays correctly when opened with either WordPad or Word 2003. However, when we load the RTF file into the RichTextBox control, or copy & paste the whole text (including the table) into the control, the table does not display correctly - the cells are only single line, without wrapping. Here are links to images showing the exact problem: Correctly displayed in WordPad Incorrectly displayed in RichTextBox control I have googled for solutions and 3rd party .net RTF controls without success. I have found this exact problem asked on another forum without an answer (in fact that's where the link to the images come from) so I'm hoping stack overflow does better ;-) My preferred solution would be to use code or a 3rd party control that can correctly render the RTF. However, I suspect the problem is that the RichTextBox control only supports a subset of the full RTF spec, so another option would be to modify the RTF directly to remove the unsupported control codes or otherwise fix the RTF file itself (in which case any information as to what control codes need to be removed or modified would be a huge help).

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  • number->string and related procedures in GIMP scheme scripting

    - by dim fish
    I am frustrated with string-to-number and number-to-string conversion in GIMP scripting. I am runnning GIMP 2.6.8 in Windows Vista. I understand that GIMP's internal Scheme implementation changes over the versions and I can't seem to nail down the documentation. From what I can gather GIMP's Scheme is a subset of TinyScheme and/or supports the R5RS standard procedures. In any case, I usually just look in the packaged script directory for examples when I want to try something new, because that should work for sure, right? For example, grid-system.scm comes with the latest GIMP release and has the expression, (string-append (number->string obj) " ") which is exactly what I want. However, if I use number-string in my own script, or even type it into GIMP's script console (which is how I usually test out new stuff I want to do) it tells me number-string is an unbound variable: > (number->string 3) Error: eval: unbound variable: number->string Other standard procedures from, say R5RS, work just fine: > (string-append "frust" "rated") "frustrated" So, 1) Is there some lurking documentation for current GIMP Scheme scripting other than something drastic like searching GIMP's source code? 2) Can I use the GIMP console to spit out a list of all defined procedures to find something I need? 3) Anyone else confirm that number-string is not defined for the current Windows build, even though it appears in the packaged scripts? My web searches haven't turned up any related problems, and a complete uninstall of all GIMP versions, back to latest puts me in the same scrape.

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  • Composite key syntax in Boost MultiIndex

    - by Sarah
    Even after studying the examples, I'm having trouble figuring out how to extract ranges using a composite key on a MultiIndex container. typedef multi_index_container< boost::shared_ptr< Host >, indexed_by< hashed_unique< const_mem_fun<Host,int,&Host::getID> >, // ID index ordered_non_unique< const_mem_fun<Host,int,&Host::getAgeInY> >, // Age index ordered_non_unique< const_mem_fun<Host,int,&Host::getHousehold> >, // Household index ordered_non_unique< // Age & eligibility status index composite_key< Host, const_mem_fun<Host,int,&Host::getAgeInY>, const_mem_fun<Host,bool,&Host::isPaired> > > > // end indexed_by > HostContainer; My goal is to get an iterator pointing to the first of the subset of elements in HostContainer hmap that has age partnerAge and returns false to Host::isPaired(): std::pair< hmap::iterator,hmap::iterator > pit = hmap.equal_range(boost::make_tuple( partnerAge, false ) ); I think this is very wrong. How/Where do I specify the iterator index (which should be 3 for age & eligibility)? I will include other composite keys in the future. What exactly are the two iterators in std::pair? (I'm copying syntax from an example that I don't understand.) I would ideally use std::count to calculate the number of elements of age partnerAge that are eligible (return false to Host::isPaired()). What is the syntax for extracting the sorted index that meets these requirements? I'm obviously still learning C++ syntax. Thanks in advance for any help.

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  • Majordomo/Mailman - Yahoo/Google Groups

    - by tom smith
    Hi. Not an app question, but thought that I might ask here anyway! The responses might help someone. I've got an app where we're going to be dealing with 5000-10000 people in a group/pool. Periodically, different subsets of people will break off in their own group. I'm looking for thoughts on how to manage/approach this situation. (For now, all of this is being managed on a few servers in the garage, with dynamic IP) I've looked into the Yahoo/google groups, and they seem to be reasonable. The primary issue that I see with this approach, is that I don't have a good way of quickly/easily alowing a subset of the group to form their own group for a given project. This kind of function is critical. The upside to this though, I wouldn't have to really set anything up. And the hosted groups could send emails to the user all day along, without running into cap/bandwidth limits The other approach is a managed list, like mailman/majordomo. This approach appears to be more flexible, and looks like ti could be modified to handle the quick creation of lists, allowing users to quickly be assigned to different lists on the fly.. The downside, I'd have to run my own Mailman/Majordomo instance, as well as the associated mail server. Or I could look at possibly using one of the hosted service.. But this is for a project on the cheap, so we're really trying to keep costs down. Thoughts/Comments/Pointers would be greatly appreciated. Thanks in advance -tom

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  • Efficient Context-Free Grammar parser, preferably Python-friendly

    - by Max Shawabkeh
    I am in need of parsing a small subset of English for one of my project, described as a context-free grammar with (1-level) feature structures (example) and I need to do it efficiently . Right now I'm using NLTK's parser which produces the right output but is very slow. For my grammar of ~450 fairly ambiguous non-lexicon rules and half a million lexical entries, parsing simple sentences can take anywhere from 2 to 30 seconds, depending it seems on the number of resulting trees. Lexical entries have little to no effect on performance. Another problem is that loading the (25MB) grammar+lexicon at the beginning can take up to a minute. From what I can find in literature, the running time of the algorithm used to parse such a grammar (Earley or CKY) should be linear to the size of the grammar and cubic to the size of the input token list. My experience with NLTK indicates that ambiguity is what hurts the performance most, not the absolute size of the grammar. So now I'm looking for a CFG parser to replace NLTK. I've been considering PLY but I can't tell whether it supports feature structures in CFGs, which are required in my case, and the examples I've seen seem to be doing a lot of procedural parsing rather than just specifying a grammar. Can anybody show me an example of PLY both supporting feature structs and using a declarative grammar? I'm also fine with any other parser that can do what I need efficiently. A Python interface is preferable but not absolutely necessary.

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  • Help matching fields between two classes

    - by Michael
    I'm not too experienced with Java yet, and I'm hoping someone can steer me in the right direction because right now I feel like I'm just beating my head against a wall... The first class is called MeasuredParams, and it's got 40+ numeric fields (height, weight, waistSize, wristSize - some int, but mostly double). The second class is a statistical classifier called Classifier. It's been trained on a subset of the MeasuredParams fields. The names of the fields that the Classifier has been trained on is stored, in order, in an array called reqdFields. What I need to do is load a new array, toClassify, with the values stored in the fields from MeasuredParams that match the field list (including order) found in reqdFields. I can make any changes necessary to the MeasuredParams class, but I'm stuck with Classifier as it is. My brute-force approach was to get rid of the fields in MeasuredParams and use an arrayList instead, and store the field names in an Enum object to act as an index pointer. Then loop through the reqdFields list, one element at a time, and find the matching name in the Enum object to find the correct position in the arrayList. Load the value stored at that positon into toClassify, and then continue on to the next element in reqdFields. I'm not sure how exactly I would search through the Enum object - it would be a lot easier if the field names were stored in a second arrayList. But then the index positions between the two would have to stay matched, and I'm back to using an Enum. I think. I've been running around in circles all afternoon, and I keep thinking there must be an easier way of doing it. I'm just stuck right now and can't see past what I've started. Any help would be GREATLY appreciated. Thanks so much! Michael

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  • Help a C# developer understand: What is a monad?

    - by Charlie Flowers
    There is a lot of talk about monads these days. I have read a few articles / blog posts, but I can't go far enough with their examples to fully grasp the concept. The reason is that monads are a functional language concept, and thus the examples are in languages I haven't worked with (since I haven't used a functional language in depth). I can't grasp the syntax deeply enough to follow the articles fully ... but I can tell there's something worth understanding there. However, I know C# pretty well, including lambda expressions and other functional features. I know C# only has a subset of functional features, and so maybe monads can't be expressed in C#. However, surely it is possible to convey the concept? At least I hope so. Maybe you can present a C# example as a foundation, and then describe what a C# developer would wish he could do from there but can't because the language lacks functional programming features. This would be fantastic, because it would convey the intent and benefits of monads. So here's my question: What is the best explanation you can give of monads to a C# 3 developer? Thanks! (EDIT: By the way, I know there are at least 3 "what is a monad" questions already on SO. However, I face the same problem with them ... so this question is needed imo, because of the C#-developer focus. Thanks.)

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  • How can a data ellipse be superimposed on a ggplot2 scatterplot?

    - by Radu
    Hi, I have an R function which produces 95% confidence ellipses for scatterplots. The output looks like this, having a default of 50 points for each ellipse (50 rows): [,1] [,2] [1,] 0.097733810 0.044957994 [2,] 0.084433494 0.050337990 [3,] 0.069746783 0.054891438 I would like to superimpose a number of such ellipses for each level of a factor called 'site' on a ggplot2 scatterplot, produced from this command: > plat1 <- ggplot(mapping=aes(shape=site, size=geom), shape=factor(site)); plat1 + geom_point(aes(x=PC1.1,y=PC2.1)) This is run on a dataset, called dflat which looks like this: site geom PC1.1 PC2.1 PC3.1 PC1.2 PC2.2 1 Buhlen 1259.5649 -0.0387975838 -0.022889782 0.01355317 0.008705276 0.02441577 2 Buhlen 653.6607 -0.0009398704 -0.013076251 0.02898955 -0.001345149 0.03133990 The result is fine, but when I try to add the ellipse (let's say for this one site, called "Buhlen"): > plat1 + geom_point(aes(x=PC1.1,y=PC2.1)) + geom_path(data=subset(dflat, site="Buhlen"),mapping=aes(x=ELLI(PC1.1,PC2.1)[,1],y=ELLI(PC1.1,PC2.1)[,2])) I get an error message: "Error in data.frame(x = c(0.0977338099339815, 0.0844334944904515, 0.0697467834016782, : arguments imply differing number of rows: 50, 211 I've managed to fix this in the past, but I cannot remember how. It seems that geom_path is relying on the same points rather than plotting new ones. Any help would be appreciated.

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  • ASP.NET required field validator firing on focus in Firefox

    - by ren33
    I have 2 asp.net textboxes in an update panel. Both textbox controls have some javascript attached to autotab to the next field and to allow only numeric input. When I enter some data into the first field and press enter, focus shifts to the next field and the requiredfieldvalidator of the second field displays its "* required" error message, even though I've just entered the field. This is only happening in Firefox. How can I prevent the validator from firing when I first enter the textbox? edit Here's the code: <asp:TextBox ID="add_ISBN" runat="server" Columns="14" MaxLength="17" CssClass="focus" /> <asp:TextBox ID="add_Qty" runat="server" Columns="4" MaxLength="4" /> <asp:RequiredFieldValidator ID="rfvQty" ControlToValidate="add_Qty" ErrorMessage="* required" ForeColor="Red" Display="Dynamic" EnableClientScript="true" ValidationGroup="Add" runat="server" /> In the codebehind: add_ISBN.Attributes.Add("onkeydown", "return isbnCheck(event, '" & add_Qty.ClientID & "')") And the javascript: function isbnCheck(e, id) { e = e || window.event; var key = e.which || e.keyCode if (validIsbnChars.indexOf(parseInt(key, 10)) >= 0) { return true; } else { if (key == 13) { var nextfield = document.getElementById(id); if (nextfield) nextfield.focus(); return false; } if (e.preventDefault) e.preventDefault(); e.returnValue = false; return false; } } The javascript allows only a valid subset of characters, and if the user presses enter, sets focus to the next field.

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  • Scaling Literate Programming?

    - by Tetha
    Greetings. I have been looking at Literate Programming a bit now, and I do like the idea behind it: you basically write a little paper about your code and write down as much of the design decisions, the code probably surrounding the module, the inner workins of the module, assumptions and conclusions resulting from the design decisions, potential extension, all this can be written down in a nice way using tex. Granted, the first point: it is documentation. It must be kept up-to-date, but that should not be that bad, because your change should have a justification and you can write that down. However, how does Literate Programming Scale to a larger degree? Overall, Literate Programming is still just text. Very human readable text, of course, but still text, and thus, it is hard to follow large systems. For example, I reworked large parts of my compiler to use and some magic to chain compile steps together, because some "x.register_follower(y); y.register_follower(z); y.register_follower(a);..." got really unwieldy, and changing that to x y z a made it a bit better, even though this is at its breaking point, too. So, how does Literate Programming scale to larger systems? Does anyone try to do that? My thought would be to use LP to specify components that communicate with each other using event streams and chain all of these together using a subset of graphviz. This would be a fairly natural extension to LP, as you can extract a documentation -- a dataflow diagram -- from the net and also generate code from it really well. What do you think of it? -- Tetha.

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  • Algorithm to match list of regular expressions

    - by DSII
    I have two algorithmic questions for a project I am working on. I have thought about these, and have some suspicions, but I would love to hear the community's input as well. Suppose I have a string, and a list of N regular expressions (actually they are wildcard patterns representing a subset of full regex functionality). I want to know whether the string matches at least one of the regular expressions in the list. Is there a data structure that can allow me to match the string against the list of regular expressions in sublinear (presumably logarithmic) time? This is an extension of the previous problem. Suppose I have the same situation: a string and a list of N regular expressions, only now each of the regular expressions is paired with an offset within the string at which the match must begin (or, if you prefer, each of the regular expressions must match a substring of the given string beginning at the given offset). To give an example, suppose I had the string: This is a test string and the regex patterns and offsets: (a) his.* at offset 0 (b) his.* at offset 1 The algorithm should return true. Although regex (a) does not match the string beginning at offset 0, regex (b) does match the substring beginning at offset 1 ("his is a test string"). Is there a data structure that can allow me to solve this problem in sublinear time? One possibly useful piece of information is that often, many of the offsets in the list of regular expressions are the same (i.e. often we are matching the substring at offset X many times). This may be useful to leverage the solution to problem #1 above. Thank you very much in advance for any suggestions you may have!

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  • Minimal-change algorithm which maximises 'swapping'

    - by Kim Bastin
    This is a question on combinatorics from a non-mathematician, so please try to bear with me! Given an array of n distinct characters, I want to generate subsets of k characters in a minimal-change order, i.e. an order in which generation n+1 contains exactly one character that was not in generation n. That's not too hard in itself. However, I also want to maximise the number of cases in which the character that is swapped out in generation n+1 is the same character that was swapped in in generation n. To illustrate, for n=7, k=3: abc abd abe* abf* abg* afg aeg* adg* acg* acd ace* acf* aef adf* ade bde bdf bef bcf* bce bcd* bcg* bdg beg* bfg* cfg ceg* cdg* cde cdf* cef def deg dfg efg The asterisked strings indicate the case I want to maximise; e.g. the e that is new in generation 3, abe, replaces a d that was new in generation 2, abd. It doesn't seem possible to have this happen in every generation, but I want it to happen as often as possible. Typical array sizes that I use are 20-30 and subset sizes around 5-8. I'm using an odd language, Icon (or actually its derivative Unicon), so I don't expect anyone to post code that I can used directly. But I will be grateful for answers or hints in pseudo-code, and will do my best to translate C etc. Also, I have noticed that problems of this kind are often discussed in terms of arrays of integers, and I can certainly apply solutions posted in such terms to my own problem. Thanks Kim Bastin

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  • Getting values from DataGridView back to XDocument (using LINQ-to-XML)

    - by Pretzel
    Learning LINQ has been a lot of fun so far, but despite reading a couple books and a bunch of online resources on the topic, I still feel like a total n00b. Recently, I just learned that if my query returns an Anonymous type, the DataGridView I'm populating will be ReadOnly (because, apparently Anonymous types are ReadOnly.) Right now, I'm trying to figure out the easiest way to: Get a subset of data from an XML file into a DataGridView, Allow the user to edit said data, Stick the changed data back into the XML file. So far I have Steps 1 and 2 figured out: public class Container { public string Id { get; set; } public string Barcode { get; set; } public float Quantity { get; set; } } // For use with the Distinct() operator public class ContainerComparer : IEqualityComparer<Container> { public bool Equals(Container x, Container y) { return x.Id == y.Id; } public int GetHashCode(Container obj) { return obj.Id.GetHashCode(); } } var barcodes = (from src in xmldoc.Descendants("Container") where src.Descendants().Count() > 0 select new Container { Id = (string)src.Element("Id"), Barcode = (string)src.Element("Barcode"), Quantity = float.Parse((string)src.Element("Quantity").Attribute("value")) }).Distinct(new ContainerComparer()); dataGridView1.DataSource = barcodes.ToList(); This works great at getting the data I want from the XML into the DataGridView so that the user has a way to manipulate the values. Upon doing a Step-thru trace of my code, I'm finding that the changes to the values made in DataGridView are not bound to the XDocument object and as such, do not propagate back. How do we take care of Step 3? (getting the data back to the XML) Is it possible to Bind the XML directly to the DataGridView? Or do I have to write another LINQ statement to get the data from the DGV back to the XDocument? Suggstions?

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  • Pros & Cons of Google App Engine

    - by Rishi
    Pros & Cons of Google App Engine [An Updated List 21st Aug 09] Help me Compile a List of all the Advantages & Disadvantages of Building an Application on the Google App Engine Pros: 1) No Need to buy Servers or Server Space (no maintenance). 2) Makes solving the problem of scaling much easier. Cons: 1) Locked into Google App Engine ?? 2)Developers have read-only access to the filesystem on App Engine. 3)App Engine can only execute code called from an HTTP request (except for scheduled background tasks). 4)Users may upload arbitrary Python modules, but only if they are pure-Python; C and Pyrex modules are not supported. 5)App Engine limits the maximum rows returned from an entity get to 1000 rows per Datastore call. 6)Java applications may only use a subset (The JRE Class White List) of the classes from the JRE standard edition. 7)Java applications cannot create new threads. Known Issues!! http://code.google.com/p/googleappengine/issues/list Hard limits Apps per developer - 10 Time per request - 30 sec Files per app - 3,000 HTTP response size - 10 MB Datastore item size - 1 MB Application code size - 150 MB Pro or Con? App Engine's infrastructure removes many of the system administration and development challenges of building applications to scale to millions of hits. Google handles deploying code to a cluster, monitoring, failover, and launching application instances as necessary. While other services let users install and configure nearly any *NIX compatible software, App Engine requires developers to use Python or Java as the programming language and a limited set of APIs. Current APIs allow storing and retrieving data from a BigTable non-relational database; making HTTP requests; sending e-mail; manipulating images; and caching. Most existing Web applications can't run on App Engine without modification, because they require a relational database.

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  • merge() multiple data frames (do.call ?)

    - by Vincent
    Hi everyone, here's my very simple question: merge() only takes two data frames as input. I need to merge a series of data frames from a list, using the same keys for every merge operation. Given a list named "test", I want to do something like: do.call("merge", test). I could write some kind of loop, but I'm wondering if there's a standard or built-in way to do this more efficiently. Any advice is appreciated. Thanks! Here's a subset of the dataset in dput format (note that merging on country is trivial in this case, but that there are more countries in the original data): test <- list(structure(list(country = c("United States", "United States", "United States", "United States", "United States"), NY.GNS.ICTR.GN.ZS = c(13.5054687, 14.7608697, 14.1115876, 13.3389063, 12.9048351), year = c(2007, 2006, 2005, 2004, 2003)), .Names = c("country", "NY.GNS.ICTR.GN.ZS", "year"), row.names = c(NA, 5L), class = "data.frame"), structure(list( country = c("United States", "United States", "United States", "United States", "United States"), NE.TRD.GNFS.ZS = c(29.3459277, 28.352838, 26.9861939, 25.6231246, 23.6615328), year = c(2007, 2006, 2005, 2004, 2003)), .Names = c("country", "NE.TRD.GNFS.ZS", "year"), row.names = c(NA, 5L), class = "data.frame"), structure(list( country = c("United States", "United States", "United States", "United States", "United States"), NY.GDP.MKTP.CD = c(1.37416e+13, 1.31165e+13, 1.23641e+13, 1.16309e+13, 1.0908e+13), year = c(2007, 2006, 2005, 2004, 2003)), .Names = c("country", "NY.GDP.MKTP.CD", "year"), row.names = c(NA, 5L), class = "data.frame"))

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  • Django Models / SQLAlchemy are bloated! Any truly Pythonic DB models out there?

    - by Luke Stanley
    "Make things as simple as possible, but no simpler." Can we find the solution/s that fix the Python database world? from someAmazingDB import * class Task (model): title = '' isDone = False db.taskList = [] #or db.taskList = expandableTypeCollection(Task) #not sure what this syntax would be db['taskList'].append(Task(title='Beat old sql interfaces',done=False)) db.taskList.append(Task('Illustrate different syntax modes',True)) #at this point it should autosave #we should be able to reload the console and access like: >> from someAmazingDB import * >> print 'Done tasks:' >> for task in db.taskList: >> if task.done: >> print task 'Illustrate different syntax modes' I'm a fan of Python, webPy and Cherry Py, and KISS in general. We're talking automatic Python to SQL type translation or NoSQL. We don't have to totally be SQL compatible! Just a scalable subset or ignore it! Re:model changes, it's ok to ask the developer when they try to change it or have a set of sensible defaults. Here is the challenge: The above code should work with very little modification or thinking required. Why must we put up with compromise when we know better? It's 2010, we should be able to code scalable, simple databases in our sleep. If you think this is important, please upvote!

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  • Should a Perl constructor return an undef or a "invalid" object?

    - by DVK
    Question: What is considered to be "Best practice" - and why - of handling errors in a constructor?. "Best Practice" can be a quote from Schwartz, or 50% of CPAN modules use it, etc...; but I'm happy with well reasoned opinion from anyone even if it explains why the common best practice is not really the best approach. As far as my own view of the topic (informed by software development in Perl for many years), I have seen three main approaches to error handling in a perl module (listed from best to worst in my opinion): Construct an object, set an invalid flag (usually "is_valid" method). Often coupled with setting error message via your class's error handling. Pros: Allows for standard (compared to other method calls) error handling as it allows to use $obj->errors() type calls after a bad constructor just like after any other method call. Allows for additional info to be passed (e.g. 1 error, warnings, etc...) Allows for lightweight "redo"/"fixme" functionality, In other words, if the object that is constructed is very heavy, with many complex attributes that are 100% always OK, and the only reason it is not valid is because someone entered an incorrect date, you can simply do "$obj->setDate()" instead of the overhead of re-executing entire constructor again. This pattern is not always needed, but can be enormously useful in the right design. Cons: None that I'm aware of. Return "undef". Cons: Can not achieve any of the Pros of the first solution (per-object error messages outside of global variables and lightweight "fixme" capability for heavy objects). Die inside the constructor. Outside of some very narrow edge cases, I personally consider this an awful choice for too many reasons to list on the margins of this question. UPDATE: Just to be clear, I consider the (otherwise very worthy and a great design) solution of having very simple constructor that can't fail at all and a heavy initializer method where all the error checking occurs to be merely a subset of either case #1 (if initializer sets error flags) or case #3 (if initializer dies) for the purposes of this question. Obviously, choosing such a design, you automatically reject option #2.

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  • Databinding question: DataGridView <=> XDocument (using LINQ-to-XML)

    - by Pretzel
    Learning LINQ has been a lot of fun so far, but despite reading a couple books and a bunch of online resources on the topic, I still feel like a total n00b. Recently, I just learned that if my query returns an Anonymous type, the DataGridView I'm populating will be ReadOnly (because, apparently Anonymous types are ReadOnly.) Right now, I'm trying to figure out the easiest way to: Get a subset of data from an XML file into a DataGridView, Allow the user to edit said data, Stick the changed data back into the XML file. So far I have Steps 1 and 2 figured out: public class Container { public string Id { get; set; } public string Barcode { get; set; } public float Quantity { get; set; } } // For use with the Distinct() operator public class ContainerComparer : IEqualityComparer<Container> { public bool Equals(Container x, Container y) { return x.Id == y.Id; } public int GetHashCode(Container obj) { return obj.Id.GetHashCode(); } } var barcodes = (from src in xmldoc.Descendants("Container") where src.Descendants().Count() > 0 select new Container { Id = (string)src.Element("Id"), Barcode = (string)src.Element("Barcode"), Quantity = float.Parse((string)src.Element("Quantity").Attribute("value")) }).Distinct(new ContainerComparer()); dataGridView1.DataSource = barcodes.ToList(); This works great at getting the data I want from the XML into the DataGridView so that the user has a way to manipulate the values. Upon doing a Step-thru trace of my code, I'm finding that the changes to the values made in DataGridView are not bound to the XDocument object and as such, do not propagate back. How do we take care of Step 3? (getting the data back to the XML) Is it possible to Bind the XML directly to the DataGridView? Or do I have to write another LINQ statement to get the data from the DGV back to the XDocument? Suggstions?

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  • MySQL get list of unique items in a SET

    - by The Disintegrator
    I have a products table with a column of type SET (called especialidad), with these possible values. [0] => NADA [1] => Freestyle / BMX [2] => Street / Dirt [3] => XC / Rural Bike [4] => All Mountain [5] => Freeride / Downhill / Dual / 4x [6] => Ruta / Triathlon / Pista [7] => Comfort / City / Paseo [8] => Kids [9] => Playera / Chopper / Custom [10] => MTB recreacion [11] => Spinning / Fitness Any given product can have one or many of these i/e "Freestyle / BMX,Street / Dirt" Given a subset of the rows, I need to get a list of all the present "especialidad" values. But I need a list to be exploded and unique Article1: "Freestyle / BMX,Street / Dirt" Article2: "Street / Dirt,Kids" Article2: "Kids" Article4: "Street / Dirt,All Mountain" Article5: "Street / Dirt" I need a list like this Freestyle / BMX Street / Dirt" Kids" All Mountain" I tried with group_concat(UNIQUE) but I get a list of the permutations...

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