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• How to write a Compiler in C for C

  - by Kerb_z

  I want to write a Compiler for C. This is a Project for my College i am doing as per my University. I am an intermediate programmer in C, with understanding of Data Structures. Now i know a Compiler has the following parts: 1. Lexer 2. Parser 3. Intermediate Code Generator 4. Optimizer 5. Code Generator I want to begin with the Lexer part and move on to Parser. I am consulting the following book: Compilers: Principles, Techniques, and Tools by Alfred V. Aho, Ravi Sethi, Jeffrey D. Ullman. The thing is that this book is highly theoretical and perplexing to me. I really appreciate the authors. But the point is i am not able to begin my project, as if i am blinded where to go. Need guidance please help.

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• HSQLDB and in-memory files

  - by lewap

  Is it possible to setup HSQLDB in a way, so that the files with the db information are written into memory instead of using actual files? I want to use hsqldb to export some data structures together with hibernate mappings. Is is, however, not possible to write temporary files, so that I need to generate the files in-memory and return a stream with their contents as a response. Setting hsqldb to use nio seems not to be a solution, because there is no way to get hold of those files before they get written onto the filesystem. What I'm thinking of is a protocol handler for hsqldb, but I didn't find a suitable solution yet. Just to describe in other words: A hack solution would be to pass hsqldb a stream or several streams. It would then during its operation write data into those streams. After all data is written, the user of the db could then use those streams to send it back over the network.

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• release vs setting-to-nil to free memory

  - by Dan Ray

  In my root view controller, in my didReceiveMemoryWarning method, I go through a couple data structures (which I keep in a global singleton called DataManager), and ditch the heaviest things I've got--one or maybe two images associated with possibly twenty or thirty or more data records. Right now I'm going through and setting those to nil. I'm also setting myself a boolean flag so that various view controllers that need this data can easily know to reload. Thusly: DataManager *data = [DataManager sharedDataManager]; for (Event *event in data.eventList) { event.image = nil; event.thumbnail = nil; } for (WondrMark *mark in data.wondrMarks) { mark.image = nil; } [DataManager sharedDataManager].cleanedMemory = YES; Today I'm thinking, though... and I'm not actually sure all that allocated memory is really being freed when I do that. Should I instead release those images and maybe hit them with a new alloc and init when I need them again later?

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• Protocol buffer deserialization and a dynamically loaded DLL in Compact Framework

  - by cloudraven

  I saw a question related to this on the full framework here. Since it seems to have stayed unresolved for quite a while and this is for the compact framework, I though it would be better to create a new question for it. I want to deserialize types for which I am loading assemblies dynamically (with Assembly.LoadFrom) and I am getting a "Unable to identify known-type for ProtoIncludeAttribute" error. In the related question I mentioned, it was hinted that hooking AppDomain.AssemblyResolve event would help solving the problem. It makes sense for the full framework, but that event is not available in the CF. I wonder if there is a way to do this with CF. The structures I am using look a lot like this and all the classes required for deserialization are loaded from the same Assembly. If the assembly is referenced instead of dynamically loaded it works fine, but fails if done dynamically.

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• How I can make Recycle Bin for Database ?Application?

  - by Wael Dalloul

  Hi, I have database application, I want to allow the user to restore the deleted records from the database, like in windows we have Recycle bin for files I want to do the same thing but for database records, Assume that I have a lot of related tables that have a lot of fields. Edit: let's say that I have the following structures: Reports table RepName primary key ReportData Users table ID primary key Name UserReports table RepName primary key UserID primary key IsDeleted now if I put isdeleted field in UserReports table, the user can't add same record again if it marked as deleted, because the record is already and this will make duplication.

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• Controlling LaTeX column flow

  - by hdhermans

  What I'm trying to do: I have a page that consists of pairs of two sentences each. The pairs are separated by a whole line break. My problem is that when I have an odd number of pairs, the second sentence will automatically be placed on the next column. How can I use LaTeX to make block structures that multicol does not ignore, to keep the two sentences together? If there's better code to solve this problem, or a better column implementation (though I don't believe I can use \twocolumn in the document declaration), please post it. My current code: \documentclass{article} \usepackage{fullpage} \usepackage{multicol} \setlength{\parindent}{0pt} \setlength{\parskip}{\baselineskip} \newcommand{\pair}[2]{ \emph{#1}\\* #2 } \begin{document} \begin{multicols}{2} \pair{Sentence 1.}{Sentence 2.} \pair{Sentence 2 (pair 2).}{Sentence 2 (pair 2).} \pair{The last pair, first sentence.}{Last sentence.} \end{multicols} \end{document} This generates: http://img541.imageshack.us/img541/3444/columns.png . The second pair is what I am trying to avoid.

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• IE7 not digesting JSON: "parse error"

  - by Kenny Leu

  While trying to GET a JSON, my callback function is NOT firing. $.ajax({ type:"GET", dataType:'json', url: myLocalURL, data: myData, success: function(returned_data){alert('success');} }); The strangest part of this is that my JSON(s) validates on JSONlint this ONLY fails on IE7...it works in Safari, Chrome, and all versions of Firefox. If I use 'error', then it reports "parseError"...even though it validates! Is there anything that I'm missing? Does IE7 not process certain characters, data structures (my data doesn't have anything non-alphanumeric, but it DOES have nested JSONs)? I have used tons of other AJAX calls that all work (even in IE7), but with the exception of THIS call. An example data return here is: {"question":{ "question_id":"19", "question_text":"testing", "other_crap":"none" }, "timestamp":{ "response":"answer", "response_text":"the text here" } } I am completely at a loss. Hopefully someone has some insight into what's going on...thank you!

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• Is there a language designed for code golf?

  - by J S

  I am not really a fan of code golf, but I have to wonder, is there an esoteric language designed for it? I mean a language with following properties: Common programs may be expressed in very short amount of characters It uses ASCII character set effectively (for example, common operators are not identifiers, so they don't have to be separated by whitespace, character usage is distributed more or less evenly because we cannot use Huffman coding and so on) Except the terse syntax, it should have very expressible and clean semantics (like, let's say, Python or Scheme); it shouldn't be difficult to program in It doesn't need features for large scale programs, such as OOP, but it definitely should allow custom functions and data structures It should have a large standard library, identifiers in this library should be as short as possible Maybe it should be called CG? Languages that can be a source of inspiration are Forth, APL and Joy.

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• Invoicing vs Quoting or Estimating

  - by FreshCode

  If invoices can be voided, should they be used as quotations? I have an Invoices tables that is created from inventory associated with a Job or Order. I could have a Quotes table as a halfway-house between inventory and invoices, but it feels like I would have duplicate data structures and logic just to handle an "Is this a quote?" bit. From a business perspective, quotes are different from invoices: a quote is sent prior to an undertaking and an invoice is sent once it is complete and payment is due, but how to represent this in my repository and model. What is an elegant way to store and manage quotes & invoices in a database? Edit: indicated Job === Order for this particular instance.

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• View controller/NIB architecture for non-navigation application with transitions?

  - by Ben

  I'm tinkering with an app that doesn't use the UINavigation root view control system, so I don't have natural ownership for each app "view". I essentially have two basic views, a document list view, and a document edit view. I'm playing with UIView animation for getting from a selected document to the edit view. I also have a toolbar that exists in both "views". Because I don't have UINavigation running the show for me, I have a tendency to just throw more and more stuff into one NIB and one view controller that owns the whole container. But now I'm trying to figure out how to segue from the document list view to the edit view if the edit view lives inside a different NIB, preserving the toolbar too. Anyone have thoughts or experience on app structures like this? I find the docs lacking on best practices around code/UI structure for anything except trivial one-screen apps or full-on navigation apps. Thanks!

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• Maximum Possible File Name Length in Windows Kernel

  - by Lambert

  I was wondering, what is the longest possible name length allowed by the Windows kernel? E.g.: I know the kernel uses UNICODE_STRING structures to hold all object paths, and since the byte length of a wide-character string is stored inside a USHORT, that allows for a maximum path length of 2^15 - 1 characters. Is there a similar, hard restriction on a file name (rather than path)? (I don't care if NTFS or FAT32 imposes a particular restriction; I'm looking for the longest possible theoretically allowed name in the kernel, assuming no additional file system or shell restrictions.) (Edit: For those wondering why this even matters, consider that normally, traversing a directory is achieved by FindFirstFile/FindNextFile calls, one call per file. Given the function named NtQueryDirectoryFile, which is the underlying system call and which returns multiple file names per call, it's actually possible to take advantage of this maximum-length restriction on the path to make an extremely-fast directory traverser that uses solely the stack as a buffer. Now I'm trying to extend that concept, and I need to know the maximum size of a file name.)

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• Most efficient way for a lookup/search in a huge list (python)

  - by user229269

  Hey guys, -- I just parsed a big file and I created a list containing 42.000 strings/words. I want to query [against this list] to check if a given word/string belongs to it. So my question is: What is the most efficient way for such a lookup? A first approach is to sort the list [list.sort()] and then just use the if word in list: print 'word' -- which is really trivial and I am sure there is a better way to do it. My goal is to apply a fast lookup that finds whether a given string is in this list or not. If you have any ideas of another data structure, they are welcome. Yet, I want to avoid for now more sophisticated data-structures like Tries etc. I am interested in hearing ideas (or tricks) about fast lookups or any other python library methods that might do the search faster than the simple 'in'. Thanks in advance!

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• How can i store data in C in a tabular format?

  - by aks

  Hi, I want to store data in C in tabular format. I am having difficulty in relating the following. Can someone help? For example: I want to store the follwong entries, then what should be the ideal way of storing in C? IP Address Domain Name 1.) 10.1.1.2 www.yahoo.com 2.) 20.1.1.3 www.google.com Should i use structures? Say for example? struct table { unsigned char ip address; char domain_name[20]; }; If not, please clarify?

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• Browser application & local file system access

  - by Beyond HTML

  I want to enhance my browser-based web application with functionality that enables management of local files and folders. E.g. folder tree structures should be synchronized between local workstation and server via HTTP(S). I am aware of security-related limitations in browser-based applications. However, there are some techniques that "work around" these issues: Signed Java applets (full trust) .NET Windows Forms browser controls (no joke, that works. Just the configuration is horrible) ActiveX My question is: What do you use/suggest, both technology and implementation practice? Key requirement is that the installation process is as simple as possible. Thanks for your opinions!

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• Building an http packet in libnet(tcp packet), Please help us as soon as posible. we are stuck!

  - by Hila

  we are building a NAT program,we change each packet that comes from our internal subnet, change it's source IP address by libnet functions.( catch the packet with libpcap, put it sniff structures and build the new packet with libnet) over TCP, the syn/ack packets are good after the change, and when a HTTP-GET request is coming, we can see by wireshark that there is an error on the checksum field.. all the other fields are exactly the same as the original packet. Is anyone knows what can cause this problem? the new checksum in other packets is calculated as it should be.. but in the HTTP packet it doesn't..

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• MSSQL "for xml", multiple tables, multiple nodes

  - by Nelson

  Is it possible to select multiple tables at once? For example, I can do: SELECT ( SELECT * FROM Articles FOR XML PATH('article'), TYPE ) FOR XML PATH('articles'), ROOT('data') and SELECT ( SELECT * FROM ArticleTypes FOR XML PATH('articleType'), TYPE ) FOR XML PATH('articleTypes'), ROOT('data') Can I join both so that I get the following output? I can't use UNION because the table structures don't match. <data> <articles> <article>...</article> ... </articles> <articleTypes> <articleType>...</articleType> ... </articleTypes> </data>

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• How to sanely read and dump structs to disk when some fields are pointers?

  - by bp

  Hello, I'm writing a FUSE plugin in C. I'm keeping track of data structures in the filesystem through structs like: typedef struct { block_number_t inode; filename_t filename; //char[SOME_SIZE] some_other_field_t other_field; } fs_directory_table_item_t; Obviously, I have to read (write) these structs from (to) disk at some point. I could treat the struct as a sequence of bytes and do something like this: read(disk_fd, directory_table_item, sizeof(fs_directory_table_item_t)); ...except that cannot possibly work as filename is actually a pointer to the char array. I'd really like to avoid having to write code like: read(disk_df, *directory_table_item.inode, sizeof(block_number_t)); read(disk_df, directory_table_item.filename, sizeof(filename_t)); read(disk_df, *directory_table_item.other_field, sizeof(some_other_field_t)); ...for each struct in the code, because I'd have to replicate code and changes in no less than three different places (definition, reading, writing). Any DRYer but still maintainable ideas?

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• Are raw C++ pointers first class objects?

  - by Shailesh Kumar

  According to Wikipedia: An object is first-class when it: can be stored in variables and data structures can be passed as a parameter to a subroutine can be returned as the result of a subroutine can be constructed at runtime has intrinsic identity (independent of any given name) Somebody had once told me that raw pointers are not first class objects while smart pointers like std::auto_ptr are. But to me, a raw pointer (to an object or to a function) in C++ does seem to me to satisfy the conditions stated above to qualify as a first class object. Am I missing something?

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• While using ConcurrentQueue, trying to dequeue while looping through in parallel

  - by James Black

  I am using the parallel data structures in my .NET 4 application and I have a ConcurrentQueue that gets added to while I am processing through it. I want to do something like: personqueue.AsParallel().WithDegreeOfParallelism(20).ForAll(i => ... ); as I make database calls to save the data, so I am limiting the number of concurrent threads. But, I expect that the ForAll isn't going to dequeue, and I am concerned about just doing ForAll(i => { personqueue.personqueue.TryDequeue(...); ... }); as there is no guarantee that I am popping off the correct one. So, how can I iterate through the collection and dequeue, in a parallel fashion. Or, would it be better to use PLINQ to do this processing, in parallel?

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• How to specify unique container styles for heterogenous hierarchies using SL3 and TreeView control

  - by rcecil

  Hello, Just look for strategies that have been successful in rendering hierarchies that represent inheritance structures using SL3/4 TreeViews. I need to render certain nodes differently than others, depending upon what kind of container they are (a choice between things, or simply a list of related things, etc.) So far, I've been very successful with the DataTemplate route: I've been able to use a technique described in Ted Glaza's post "Easy DataTemplateSelectors in Silverlight" (you may have retrieve a Google cache of this page). SO what I'm trying to discover is something on the order of a StyleSelector, not a DataTemplateSelector. I'm considering leveraging my current implementations of Glaza's pattern of selector objects to somehow detect the node type and set the ItemContainerStyle there, but it doesn't seem clear right now. Thanks for your thoughts.

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• Flexibility starting to develop applications and DB

  - by kristaps

  Hi! First of all I want to say some info for admins. This post can help to all DBA and developers. Hope You don't close this. I'm writing about widespread problem I'm writing master work and I want that You will had little time to answer my questions in my form. These questions are about db structures. Visit here: http://spreadsheets.google.com/embeddedform?formkey=dEhmOWFGb2twWVFreWJwWXp2U3c5a1E6MQ After I summarized results, I insert it in new post and developers can choose which structure to use to reach needed requirements developing new applications. I think that my test will help a lot of people. Best regards, Kristaps

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• O(log N) == O(1) - Why not?

  - by phoku

  Whenever I consider algorithms/data structures I tend to replace the log(N) parts by constants. Oh, I know log(N) diverges - but does it matter in real world applications? log(infinity) < 100 for all practical purposes. I am really curious for real world examples where this doesn't hold. To clarify: I understand O(f(N)) I am curious about real world examples where the asymptotic behaviour matters more than the constants of the actual performance. If log(N) can be replaced by a constant it still can be replaced by a constant in O( N log N). This question is for the sake of (a) entertainment and (b) to gather arguments to use if I run (again) into a controversy about the performance of a design.

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• C++ library for Coordinate Transformation Matrices (CTM)?

  - by BastiBense

  I'm looking for a C++ library which allows for easy integration of Coordinate Transformation Matrices (CTM) in my application. You might know CTMs from PDF or PostScript. For one project we are using C++/Qt4 as a framework, which offers a QTransform class, which provides methods like .translate(double x, double y) or .rotate(double degrees). After doing some transformations, it would allow me to get all 6 CTM values, which I could feed into a PDF library or use a transformation matrix in export files. Qt's API also allows for arbitrary mapping of polygons (QPolygon), rectangles (QRect) and other primitive data structures into transformed coordinate systems. So basically I'm looking for something similar to what Qt provides, but without the need of using Qt. I know I could do the matrix multiplications myself, but I'm not really interested in doing so, as I'm very sure that someone already solved this problem, so please no links to books or other guides on how to multiply matrices. Thanks!

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• Are memory barriers necessary for atomic reference counting shared immutable data?

  - by Dietrich Epp

  I have some immutable data structures that I would like to manage using reference counts, sharing them across threads on an SMP system. Here's what the release code looks like: void avocado_release(struct avocado *p) { if (atomic_dec(p->refcount) == 0) { free(p->pit); free(p->juicy_innards); free(p); } } Does atomic_dec need a memory barrier in it? If so, what kind of memory barrier? Additional notes: The application must run on PowerPC and x86, so any processor-specific information is welcomed. I already know about the GCC atomic builtins. As for immutability, the refcount is the only field that changes over the duration of the object.

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• Storage for large gridded datasets

  - by nullglob

  I am looking for a good storage format for large, gridded datasets. The application is meteorology, and we would prefer a format that is common within this field (to help exchange data with others). I don't need to deal with special data structures, and there should be a Fortran API. I am currently considering HDF5, GRIB2 and NetCDF4. How do these formats compare in terms of data compression? What are their main limitations? How steep is the learning curve? Are there any other storage formats worth investigating? I have not found a great deal of material outlining the differences and pros/cons of these formats (there is one relevant SO thread, and a presentation comparing GRIB and NetCDF).

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