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  • Choice of programming language for learning data structures and algorithms

    - by bguiz
    Which programming language would you recommend to learn about data structures and algorithms in? Considering the follwing: Personal experience Language features (pointers, OO, etc) Suitability for learning DS & A concepts I ask because there are some books out there that are programming language-agnostic (written from a Mathematical perspective, and use pseudocode). If I learn from one of these I would like to work out the algorithms in a chosen language. Then, there are other books which introduce DS & A concepts with examples in a particular programming laguage - and I would follow these examples as well. Either way, I have to choose a language, and I would like to stick to one throughout. Which one best fits the bill.

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  • Algorithm for Determining Variations of Differing Lengths

    - by joseph.ferris
    I have four objects - for the sake of arguments, let say that they are the following letters: A B C D I need to calculate the number of variations that can be made for these under the following two conditions: No repetition Objects are position agnostic Taking the above, this means that with a four object sequence, I can have only one sequence that matches the criteria (since order is not considered for being unique): ABCD There are four variations for a three object combination from the four object pool: ABC, ABD, ACD, and BCD There are six variations for a two object combination from the four object pool: AB, AC, AD, BC, BD, and CD And the most simple one, if taken on at a time: A, B, C, and D I swear that this was something covered in school, many, many years ago - and probably forgotten since I didn't think I would use it. :-) I am anticipating that factorials will come into play, but just trying to force an equation is not working. Any advice would be appreciated.

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  • Determining whether a file is a duplicate

    - by Todd R
    Is there a reliable way to determine whether or not two files are the same? For example, two files with the same size and type may or may not be the same binarilly (yeah, I know it's not really a word). I assume that comparing one or two checksums of the files will help, but I wonder: How reliable are checksums at determining whether two files are different; what are the chances of two different files having the same checksum? Would reliability increase by applying additional checksum comparisons? Which checksum algorithm(s) would be the most efficient and/or reliable? Any ideas, suggestions or thoughts are appreciated! P.S. The code for this is being written in Java running on a nix system, but generic or platform agnostic input is most helpful.

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  • What's the right way to handle "One, Both, or None" logic?

    - by Stephen
    I have a logic situation that is best described as two "Teams" trying to win a task. The outcome of this task could be a single winner, a tie (draw), or no winner (stalemate). Currently, I'm using a nested if/else statement like so: // using PHP, but the concept seems language agnostic. if ($team_a->win()) { if ($team_b->win()) { // this is a draw } else { // team_a is the winner } } else { if ($team_b->win()) { // team_b is the winner } else { // This is a stalemate, no winner. } } This seems rather spaghetti-like and repetitive. Is there a more logical, DRY pattern I could use?

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  • Reference table values in a war against magic numbers

    - by Alex N.
    This question bugged me for years now and can't seem to find good solution still. I working in PHP and Java but it sounds like this maybe language-agnostic :) Say we have a standard status reference table that holds status ids for some kind of entity. Further let's assume the table will have just 5 values, and will remain like this for a long time, maybe edited occasionally with addition of a new status. When you fetch a row and need to see what status it is you have 2 options(as I see it at least) - put it straight ID values(magic numbers that is) or use a named constant. Latter seem much cleaner, the question though is where those named constants should leave? In a model class? In a class that uses this particular constant? Somewhere else?

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  • Data storage advice needed: Best way to store location + time data?

    - by sobedai
    I have a project in mind that will require the majority of queries to be keyed off of lat/long as well as date + time. Initially, I was thinking of a standard RDBMS where lat, long, and the datetime field are properly indexed. Then, I began thinking of a document based system where the document was essentially a timestamp and each document has lat/long with in it. Each document could have n objects associated with it. I'm looking for advice on what would be the best type of storage engine for this sort of thing is - which of the above idea would be better or if there is something else completely that is the ideal solution. Thanks

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  • running code when two events have triggered

    - by Evert
    This is mostly a language-agnostic question. If I'm waiting for two events to complete (say, two IO events or http requests), what is the best pattern to deal with this. One thing I can think of is the following (pseudo js example). request1.onComplete = function() { req1Completed = true; eventsCompleted(); } request2.onComplete = function() { req2Completed = true; eventsCompleted(); } eventsCompleted = function() { if (!req1Completed || !req2Completed) return; // do stuff } Is this the most effective pattern, or are there more elegant ways to solve this issue?

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  • Configure PERL DBI and DBD in Linux

    - by Balualways
    I am new to Perl and I work in a Linux OEL 5x server. I am trying to configure the Perl DB modules for Oracle connectivity (DBD and DBI modules). Can anyone help me out in the installation procedure? I had tried CPAN didn't really worked out. Any help would be appreciated. I am not quite sure I need to initialize any variables other than $LD_LIBRARY_PATH and $ORACLE_HOME These are my observations: ISSUE:: I am getting the following issue while using the DBI module to connect to Oracle: install_driver(Oracle) failed: Can't locate loadable object for module DBD::Oracle in @INC (@INC contains: /usr/lib64/perl5/site_perl/5.8.8/x86_64-linux-thread-multi /usr/lib/perl5/site_perl/5.8.8 /usr/lib/perl5/site_perl /usr/lib64/perl5/vendor_perl/5.8.8/x86_64-linux-thread-multi /usr/lib/perl5/vendor_perl/5.8.8 /usr/lib/perl5/vendor_perl /usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi /usr/lib/perl5/5.8.8 .) at (eval 3) line 3 Compilation failed in require at (eval 3) line 3. Perhaps a module that DBD::Oracle requires hasn't been fully installed at connectdb.pl line 57 I had installed the DBD for oracle from /usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi/DBD/DBD-Oracle-1.50 Could you please take a look into the steps and correct me if I am wrong: Observations: $ echo $LD_LIBRARY_PATH /opt/CA/UnicenterAutoSysJM/autosys/lib:/opt/CA/SharedComponents/Csam/SockAdapter/lib:/opt/CA/SharedComponents/ETPKI/lib:/opt/CA/CAlib $ echo $ORACLE_HOME /usr/local/oracle/ORA This is how I tried to install the DBD module: Download the file DBD 1.50 for Oracle Copy to /usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi/DBD Untar and Makefile.PL . Message: Using DBI 1.52 (for perl 5.008008 on x86_64-linux-thread-multi) installed in /usr/lib64/perl5/vendor_perl/5.8.8/x86_64-linux-thread-multi/auto/DBI/ Configuring DBD::Oracle for perl 5.008008 on linux (x86_64-linux-thread-multi) Remember to actually *READ* the README file! Especially if you have any problems. Installing on a linux, Ver#2.6 Using Oracle in /opt/oracle/product/10.2 DEFINE _SQLPLUS_RELEASE = "1002000400" (CHAR) Oracle version 10.2.0.4 (10.2) Found /opt/oracle/product/10.2/rdbms/demo/demo_rdbms.mk Found /opt/oracle/product/10.2/rdbms/demo/demo_rdbms64.mk Found /opt/oracle/product/10.2/rdbms/lib/ins_rdbms.mk Using /opt/oracle/product/10.2/rdbms/demo/demo_rdbms.mk Your LD_LIBRARY_PATH env var is set to '/usr/local/oracle/ORA/lib:/usr/dt/lib:/usr/openwin/lib:/usr/local/oracle/ORA/ows/cartx/wodbc/1.0/util/lib:/usr/local/oracle/ORA/lib:/usr/local/sybase/OCS-12_0/lib:/usr/local/sybase/lib:/home/oracle/jdbc/jdbcoci73/lib:./' WARNING: Your LD_LIBRARY_PATH env var doesn't include '/opt/oracle/product/10.2/lib' but probably needs to. Reading /opt/oracle/product/10.2/rdbms/demo/demo_rdbms.mk Reading /usr/local/oracle/ORA/rdbms/lib/env_rdbms.mk Attempting to discover Oracle OCI build rules sh: make: command not found by executing: [make -f /opt/oracle/product/10.2/rdbms/demo/demo_rdbms.mk build ECHODO=echo ECHO=echo GENCLNTSH='echo genclntsh' CC=true OPTIMIZE= CCFLAGS= EXE=DBD_ORA_EXE OBJS=DBD_ORA_OBJ.o] WARNING: Oracle build rule discovery failed (32512) Add path to make command into your PATH environment variable. Oracle oci build prolog: [sh: make: command not found] Oracle oci build command: [] WARNING: Unable to interpret Oracle build commands from /opt/oracle/product/10.2/rdbms/demo/demo_rdbms.mk. (Will continue by using fallback approach.) Please report this to [email protected]. See README for what to include. Found header files in /opt/oracle/product/10.2/rdbms/public. client_version=10.2 DEFINE= -Wall -Wno-comment -DUTF8_SUPPORT -DORA_OCI_VERSION=\"10.2.0.4\" -DORA_OCI_102 Checking for functioning wait.ph System: perl5.008008 linux ca-build9.us.oracle.com 2.6.20-1.3002.fc6xen #1 smp thu apr 30 18:08:39 pdt 2009 x86_64 x86_64 x86_64 gnulinux Compiler: gcc -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -Wdeclaration-after-statement -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm Linker: not found Sysliblist: -ldl -lm -lpthread -lnsl -lirc Oracle makefiles would have used these definitions but we override them: CC: cc CFLAGS: $(GFLAG) $(OPTIMIZE) $(CDEBUG) $(CCFLAGS) $(PFLAGS)\ $(SHARED_CFLAG) $(USRFLAGS) [$(GFLAG) -O3 $(CDEBUG) -m32 $(TRIGRAPHS_CCFLAGS) -fPIC -I/usr/local/oracle/ORA/rdbms/demo -I/usr/local/oracle/ORA/rdbms/public -I/usr/local/oracle/ORA/plsql/public -I/usr/local/oracle/ORA/network/public -DLINUX -D_GNU_SOURCE -D_LARGEFILE64_SOURCE=1 -D_LARGEFILE_SOURCE=1 -DSLTS_ENABLE -DSLMXMX_ENABLE -D_REENTRANT -DNS_THREADS -fno-strict-aliasing $(LPFLAGS) $(USRFLAGS)] build: $(CC) $(ORALIBPATH) -o $(EXE) $(OBJS) $(OCISHAREDLIBS) [ cc -L$(LIBHOME) -L/usr/local/oracle/ORA/rdbms/lib/ -o $(EXE) $(OBJS) -lclntsh $(EXPDLIBS) $(EXOSLIBS) -ldl -lm -lpthread -lnsl -lirc -ldl -lm $(USRLIBS) -lpthread] LDFLAGS: $(LDFLAGS32) [-m32 -o $@ -L/usr/local/oracle/ORA/rdbms//lib32/ -L/usr/local/oracle/ORA/lib32/ -L/usr/local/oracle/ORA/lib32/stubs/] Linking with /usr/local/oracle/ORA/rdbms/lib/defopt.o -lclntsh -ldl -lm -lpthread -lnsl -lirc -ldl -lm -lpthread [from $(DEF_OPT) $(OCISHAREDLIBS)] Checking if your kit is complete... Looks good LD_RUN_PATH=/usr/local/oracle/ORA/lib Using DBD::Oracle 1.50. Using DBD::Oracle 1.50. Using DBI 1.52 (for perl 5.008008 on x86_64-linux-thread-multi) installed in /usr/lib64/perl5/vendor_perl/5.8.8/x86_64-linux-thread-multi/auto/DBI/ Writing Makefile for DBD::Oracle Writing MYMETA.yml and MYMETA.json *** If you have problems... read all the log printed above, and the README and README.help.txt files. (Of course, you have read README by now anyway, haven't you?)

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  • Simulating aspects of static-typing in a duck-typed language

    - by Mike
    In my current job I'm building a suite of Perl scripts that depend heavily on objects. (using Perl's bless() on a Hash to get as close to OO as possible) Now, for lack of a better way of putting this, most programmers at my company aren't very smart. Worse, they don't like reading documentation and seem to have a problem understanding other people's code. Cowboy coding is the game here. Whenever they encounter a problem and try to fix it, they come up with a horrendous solution that actually solves nothing and usually makes it worse. This results in me, frankly, not trusting them with code written in duck typed language. As an example, I see too many problems with them not getting an explicit error for misusing objects. For instance, if type A has member foo, and they do something like, instance->goo, they aren't going to see the problem immediately. It will return a null/undefined value, and they will probably waste an hour finding the cause. Then end up changing something else because they didn't properly identify the original problem. So I'm brainstorming for a way to keep my scripting language (its rapid development is an advantage) but give an explicit error message when an an object isn't used properly. I realize that since there isn't a compile stage or static typing, the error will have to be at run time. I'm fine with this, so long as the user gets a very explicit notice saying "this object doesn't have X" As part of my solution, I don't want it to be required that they check if a method/variable exists before trying to use it. Even though my work is in Perl, I think this can be language agnostic.

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  • Program Structure Design Tools? (Top Down Design)

    - by Lee Olayvar
    I have been looking to expand my methodologies to better involve Unit testing, and i stumbled upon Behavioral Driven Design (Namely Cucumber, and a few others). I am quite intrigued by the concept as i have never been able to properly design top down, only because keeping track of the design gets lost without a decent way to record it. So on that note, in a mostly language agnostic way, are there any useful tools out there i am (probably) unaware of? Eg, i have often been tempted to try building flow charts for my programs, but i am not sure how much that will help, and it seems a bit confusing to me how i could make a complex enough flow chart to handle the logic of a full program, and all its features.. ie, it just seems like flow charts would be limiting in the design scheme.. or possibly grow to an unmaintainable scale. BDD methods are nice, but with a system that is so tied to structure, tying into the language and unit testing seems like a must (for it to be worth it) and it seems to be hard to find something to work well with both Python and Java (my two main languages). So anyway.. on that note, any comments are much appreciated. I have searched around on here and it seems like top down design is a well discussed topic, but i haven't seen too much reference to tools themselves, eg, flow chart programs, etc. I am on Linux, if it matters (in the case of programs).

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  • What Language Feature Can You Just Not Live Without?

    - by akdom
    I always miss python's built-in doc strings when working in other languages. I know this may seem odd, but it allows me to cut down significantly on excess comments while still providing a clean description of my code and any interfaces therein. What Language Feature Can You Just Not Live Without? If someone were building a new language and they asked you what one feature they absolutely must include, what would it be? This is getting kind of long, so I figured I'd do my best to summarize: Paraphrased to be language agnostic. If you know of a language which uses something mentioned, please at it in the parenthesis to the right of the feature. And if you have a better format for this list, by all means try it out (if it doesn't seem to work, I'll just roll back). Regular Expressions ~ torial (Perl) Garbage Collection ~ SaaS Developer (Python, Perl, Ruby, Java, .NET) Anonymous Functions ~ Vinko Vrsalovic (Lisp, Python) Arithmetic Operators ~ Jeremy Ross (Python, Perl, Ruby, Java, C#, Visual Basic, C, C++, Pascal, Smalltalk, etc.) Exception Handling ~ torial (Python, Java, .NET) Pass By Reference ~ Chris (Python) Unified String Format WalloWizard (C#) Generics ~ torial (Python, Java, C#) Integrated Query Equivalent to LINQ ~ Vyrotek (C#) Namespacing ~ Garry Shutler () Short Circuit Logic ~ Adam Bellaire ()

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  • Design pattern to use instead of multiple inheritance

    - by mizipzor
    Coming from a C++ background, Im used to multiple inheritance. I like the feeling of a shotgun squarely aimed at my foot. Nowadays, I work more in C# and Java, where you can only inherit one baseclass but implement any number of interfaces (did I get the terminology right?). For example, lets consider two classes that implement a common interface but different (yet required) baseclasses: public class TypeA : CustomButtonUserControl, IMagician { public void DoMagic() { // ... } } public class TypeB : CustomTextUserControl, IMagician { public void DoMagic() { // ... } } Both classes are UserControls so I cant substitute the base class. Both needs to implement the DoMagic function. My problem now is that both implementations of the function are identical. And I hate copy-and-paste code. The (possible) solutions: I naturally want TypeA and TypeB to share a common baseclass, where I can write that identical function definition just once. However, due to having the limit of just one baseclass, I cant find a place along the hierarchy where it fits. One could also try to implement a sort of composite pattern. Putting the DoMagic function in a separate helper class, but the function here needs (and modifies) quite a lot of internal variables/fields. Sending them all as (reference) parameters would just look bad. My gut tells me that the adapter pattern could have a place here, some class to convert between the two when necessery. But it also feels hacky. I tagged this with language-agnostic since it applies to all languages that use this one-baseclass-many-interfaces approach. Also, please point out if I seem to have misunderstood any of the patterns I named. In C++ I would just make a class with the private fields, that function implementation and put it in the inheritance list. Whats the proper approach in C#/Java and the like?

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  • Best way to enforce inter-table constraints inside database

    - by FerranB
    I looking for the best way to check for inter-table constraints an step forward of foreing keys. For instance, to check if a date child record value is between a range date on two parent rows columns. For instance: Parent table ID DATE_MIN DATE_MAX ----- ---------- ---------- 1 01/01/2009 01/03/2009 ... Child table PARENT_ID DATE ---------- ---------- 1 01/02/2009 1 01/12/2009 <--- HAVE TO FAIL! ... I see two approaches: Create materialized views on-commit as shown in this article (or other equivalent on other RDBMS). Use stored-procedures and triggers. Any other approach? Which is the best option? UPDATE: The motivation of this question is not about "putting the constraints on database or on application". I think this is a tired question and anyone does the way she loves. And, I'm sorry for detractors, I'm developing with constraints on database. From here, the question is "which is the best option to manage inter-table constraints on database?". I'm added "inside database" on the question title. UPDATE 2: Some one added the "oracle" tag. Of course materialized views are oracle-tools but I'm interested on any option regardless it's on oracle or others RDBMSs.

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  • is there a Universal Model for languages?

    - by Smandoli
    Many programming languages share generic and even fairly universal features. For example, if you compared Java, VB6, .NET, PHP, Python, then you would find common functions such as control structures, numeric and string manipulation, etc. What has been done to define these features at a meta-language (or language-agnostic) level? UML offers a descriptive reference of software in every aspect, but the real-world focus seems to be data processes. Is UML relevant? I'm not asking "Why we don't have a single language that replaces the current plethora." We need many different tools (at least in this eon). I'm not asking that all languages fit a template -- assembly vs. compiled languages are different enough to make that unfeasible (and some folks call HTML a language, though I wouldn't). Any attempt would start with a properly narrow scope. In line with this, I wouldn't expect the model to cover even a small selection with full validity. I would expect however that such a model could be used to transpose from one language to another (with limited goals -- think jist translation).

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  • Is this a variation of the traveling salesman problem?

    - by Ville Koskinen
    I'm interested in a function of two word lists, which would return an order agnostic edit distance between them. That is, the arguments would be two lists of (let's say space delimited) words and return value would be the minimum sum of the edit (or Levenshtein) distances of the words in the lists. Distance between "cat rat bat" and "rat bat cat" would be 0. Distance between "cat rat bat" and "fat had bad" would be the same as distance between "rat bat cat" and "had fat bad", 4. In the case the number of words in the lists are not the same, the shorter list would be padded with 0-length words. My intuition (which hasn't been nurtured with computer science classes) does not find any other solution than to use brute force: |had|fat|bad| a solution ---+---+---+---+ +---+---+---+ cat| 2 | 1 | 2 | | | 1 | | ---+---+---+---+ +---+---+---+ rat| 2 | 1 | 2 | | 3 | | | ---+---+---+---+ +---+---+---+ bat| 2 | 1 | 1 | | | | 4 | ---+---+---+---+ +---+---+---+ Starting from the first row, pick a column and go to the next rows without ever revisiting a column you have already visited. Do this over and over again until you've tried all combinations. To me this sounds a bit like the traveling salesman problem. Is it, and how would you solve my particular problem?

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  • should the builder reset its build environment after delivering the product

    - by Sudhi
    I am implementing a builder where in the deliverable is retrieved by calling Builder::getProduct() . The director asks various parts to build Builder::buildPartA() , Builder::buildPartB() etc. in order to completely build the product. My question is, once the product is delivered by the Builder by calling Builder::getProduct(), should it reset its environment (Builder::partA = NULL;, Builder::partB = NULL;) so that it is ready to build another product? (with same or different configuration?) I ask this as I am using PHP wherein the objects are by default passed by reference (nope, I don't want to clone them, as one of their field is a Resource) . However, even if you think from a language agnostic point of view, should the Builder reset its build environment ? If your answer is 'it depends on the case' what use cases would justify reseting the environment (and other way round) ? For the sake of providing code sample here's my Builder::gerProcessor() which shows what I mean by reseting the environment /** * @see IBuilder::getProessor() */ public function getProcessor() { if($this->_processor == NULL) { throw new LogicException('Processor not yet built!'); } else { $retval = $this->_processor; $this->_product = NULL, $this->_processor = NULL; } return $retval; }

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  • Should client-server code be written in one "project" or two?

    - by Ricket
    I've been beginning a client-server application. At first I naturally created two projects in Eclipse, two source control repositories, etc. But I'm quickly seeing that there is a bit of shared code between the two that would probably benefit to sharing instead of copying. In addition, I've been learning and trying test-driven development, and it seems to me that it would be easier to test based on real client components rather than having to set up a huge amount of code just to mock something, when the code is probably mostly in the client. My biggest concern in merging the client and server is of security; how do I ensure that the server pieces of the code do not reach an user's computer? So especially if you are writing client-server applications yourself (and especially in Java, though this can turn into a language-agnostic question if you'd like to share your experience with this in other languages), what sort of separation do you keep between your client and server code? Are they just in different packages/namespaces or completely different binaries using shared libraries, or something else entirely? How do you test the code together and yet ship separately?

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  • How to keep confirmation messages after POST while doing a post-submit redirect?

    - by MicE
    Hello, I'm looking for advise on how to share certain bits of data (i.e. post-submit confirmation messages) between individual requests in a web application. Let me explain: Current approach: user submits an add/edit form for a resource if there were no errors, user is shown a confirmation with links to: submit a new resource (for "add" form) view the submitted/edited resource view all resources (one step above in hierarchy) user then has to click on one of the three links to proceed (i.e. to the page "above") Progmatically, the form and its confirmation page are one set of classes. The page above that is another. They can technically share code, but at the moment they are both independent during processing of individual requests. We would like to amend the above as follows: user submits an add/edit form for a resource if there were no errors, the user is redirected to the page with all resources (one step above in hierarchy) with one or more confirmation messages displayed at the top of the page (i.e. success message, to whom was the request assigned, etc) This will: save users one click (they have to go through a lot of these add/edit forms) the post-submit redirect will address common problems with browser refresh / back-buttons What approach would you recommend for sharing data needed for the confirmation messages between the two requests, please? I'm not sure if it helps, it's a PHP application backed by a RESTful API, but I think that this is a language-agnostic question. A few simple solutions that come to mind are to share the data via cookies or in the session, this however breaks statelessness and would pose a significant problem for users who work in several tabs (the data could clash together). Passing the data as GET parameters is not suitable as we are talking about several messages which are dynamic (e.g. changing actors, dates). Thanks, M.

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  • How would I code a complex formula parser manually?

    - by StormianRootSolver
    Hm, this is language - agnostic, I would prefer doing it in C# or F#, but I'm more interested this time in the question "how would that work anyway". What I want to accomplish ist: a) I want to LEARN it - it's about my ego this time, it's for a fun project where I want to show myself that I'm a really good at this stuff b) I know a tiny little bit about EBNF (although I don't know yet, how operator precedence works in EBNF - Irony.NET does it right, I checked the examples, but this is a bit ominous to me) c) My parser should be able to take this: 5 * (3 + (2 - 9 * (5 / 7)) + 9) for example and give me the right results d) To be quite frankly, this seems to be the biggest problem in writing a compiler or even an interpreter for me. I would have no problem generating even 64 bit assembler code (I CAN write assembler manually), but the formula parser... e) Another thought: even simple computers (like my old Sharp 1246S with only about 2kB of RAM) can do that... it can't be THAT hard, right? And even very, very old programming languages have formula evaluation... BASIC is from 1964 and they already could calculate the kind of formula I presented as an example f) A few ideas, a few inspirations would be really enough - I just have no clue how to do operator precedence and the parentheses - I DO, however, know that it involves an AST and that many people use a stack So, what do you think?

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  • Program structure in long running data processing python script

    - by fmark
    For my current job I am writing some long-running (think hours to days) scripts that do CPU intensive data-processing. The program flow is very simple - it proceeds into the main loop, completes the main loop, saves output and terminates: The basic structure of my programs tends to be like so: <import statements> <constant declarations> <misc function declarations> def main(): for blah in blahs(): <lots of local variables> <lots of tightly coupled computation> for something in somethings(): <lots more local variables> <lots more computation> <etc., etc.> <save results> if __name__ == "__main__": main() This gets unmanageable quickly, so I want to refactor it into something more manageable. I want to make this more maintainable, without sacrificing execution speed. Each chuck of code relies on a large number of variables however, so refactoring parts of the computation out to functions would make parameters list grow out of hand very quickly. Should I put this sort of code into a python class, and change the local variables into class variables? It doesn't make a great deal of sense tp me conceptually to turn the program into a class, as the class would never be reused, and only one instance would ever be created per instance. What is the best practice structure for this kind of program? I am using python but the question is relatively language-agnostic, assuming a modern object-oriented language features.

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  • CakePHP Multiple Nested Joins

    - by Paul
    I have an App in which several of the models are linked by hasMany/belongsTo associations. So for instance, A hasMany B, B hasMany C, C hasMany D, and D hasMany E. Also, E belongs to D, D belongs to C, C belongs to B, and B belongs to A. Using the Containable behavior has been great for controlling the amount of information comes back with each query, but I seem to be having a problem when trying to get data from table A while using a condition that involves table D. For instance, here is an example of my 'A' model: class A extends AppModel { var $name = 'A'; var $hasMany = array( 'B' => array('dependent' => true) ); function findDependentOnE($condition) { return $this->find('all', array( 'contain' => array( 'B' => array( 'C' => array( 'D' => array( 'E' => array( 'conditions' => array( 'E.myfield' => $some_value ) ) ) ) ) ) )); } } This still gives me back all the records in 'A', and if it's related 'E' records don't satisfy the condition, then I just get this: Array( [0] => array( [A] => array( [field1] => // stuff [field2] => // more stuff // ...etc ), [B] => array( [field1] => // stuff [field2] => // more stuff // ...etc ), [C] => array( [field1] => // stuff [field2] => // more stuff // ...etc ), [D] => array( [field1] => // stuff [field2] => // more stuff // ...etc ), [E] => array( // empty if 'E.myfield' != $some_value' ) ), [1] => array( // ...etc ) ) When If 'E.myfield' != $some_value, I don't want the record returned at all. I hope this expresses my problem clearly enough... Basically, I want the following query, but in a database-agnostic/CakePHP-y kind of way: SELECT * FROM A INNER JOIN (B INNER JOIN (C INNER JOIN (D INNER JOIN E ON D.id=E.d_id) ON C.id=D.c_id) ON B.id=C.b_id) ON A.id=B.a_id WHERE E.myfield = $some_value

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  • Algorithm to Render a Horizontal Binary-ish Tree in Text/ASCII form

    - by Justin L.
    It's a pretty normal binary tree, except for the fact that one of the nodes may be empty. I'd like to find a way to output it in a horizontal way (that is, the root node is on the left and expands to the right). I've had some experience expanding trees vertically (root node at the top, expanding downwards), but I'm not sure where to start, in this case. Preferably, it would follow these couple of rules: If a node has only one child, it can be skipped as redundant (an "end node", with no children, is always displayed) All nodes of the same depth must be aligned vertically; all nodes must be to the right of all less-deep nodes and to the left of all deeper nodes. Nodes have a string representation which includes their depth. Each "end node" has its own unique line; that is, the number of lines is the number of end nodes in the tree, and when an end node is on a line, there may be nothing else on that line after that end node. As a consequence of the last rule, the root node should be in either the top left or the bottom left corner; top left is preferred. For example, this is a valid tree, with six end nodes (node is represented by a name, and its depth): [a0]------------[b3]------[c5]------[d8] \ \ \----------[e9] \ \----[f5] \--[g1]--------[h4]------[i6] \ \--------------------[j10] \-[k3] Which represents the horizontal, explicit binary tree: 0 a / \ 1 g * / \ \ 2 * * * / \ \ 3 k * b / / \ 4 h * * / \ \ \ 5 * * f c / \ / \ 6 * i * * / / \ 7 * * * / / \ 8 * * d / / 9 * e / 10 j (branches folded for compactness; * representing redundant, one-child nodes; note that *'s are actual nodes, storing one child each, just with names omitted here for presentation sake) (also, to clarify, I'd like to generate the first, horizontal tree; not this vertical tree) I say language-agnostic because I'm just looking for an algorithm; I say ruby because I'm eventually going to have to implement it in ruby anyway. Assume that each Node data structure stores only its id, a left node, and a right node. A master Tree class keeps tracks of all nodes and has adequate algorithms to find: A node's nth ancestor A node's nth descendant The generation of a node The lowest common ancestor of two given nodes Anyone have any ideas of where I could start? Should I go for the recursive approach? Iterative?

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  • The 80 column limit, still useful?

    - by Tim Post
    Related: While coding, how many columns do you format for? Is there a valid reason for enforcing a maximum width of 80 characters in a code file, this day and age? I mostly use C, however this question is language agnostic. Its also subjective, so I'll tag it as such. Many individual projects set their own various coding standards, a guide to adjust your coding style. Many enforce an 80 column limit on code, i.e. don't force a dumb 80 x 25 terminal to wrap your lines in someone else's editor of choice if they are stuck with such a display, don't force them to turn off wrapping. Both private and open source projects usually have some style guidelines. My question is, in this day and age, is that requirement more of a pest than a helper? Does anyone still login via the local console with no framebuffer and actually edit code? If so, how often and why cant you use SSH? I help to manage a few open source projects, I was considering extending this limit to 110 columns, but I wanted to get feedback first. So, any feedback is appreciated. I can see the need to make certain OUTPUT of programs (i.e. a --help /h display) 80 columns or less, but I really don't see the need to force people to break up code under 110 columns long into 2 lines, when its easier to read on one line. I can also see the case for adhering to an 80 column limit if you're writing code that will be used on micro controllers that have to be serviced in the field with a god-knows-what terminal emulator. Beyond that, what are your thoughts? Edit: This is not an exact duplicate. I am asking very specific questions, such as how many people are actually still using such a display. I am also not asking "what is a good column limit", I'm proposing one and hoping to gather feedback. Beyond that, I'm also citing cases where the 80 column limit is still a good idea. I don't want a guide to my own "c-style", I'm hoping to adjust standards for several projects. If the duplicate in question had answered all of my questions, I would not have posted this one :) That will teach me to mention it next time. Edit 2 question |= COMMUNITY_WIKI

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  • Finding open contiguous blocks of time for every day of a month, fast

    - by Chris
    I am working on a booking availability system for a group of several venues, and am having a hard time generating the availability of time blocks for days in a given month. This is happening server-side in PHP, but the concept itself is language agnostic -- I could be doing this in JS or anything else. Given a venue_id, month, and year (6/2012 for example), I have a list of all events occurring in that range at that venue, represented as unix timestamps start and end. This data comes from the database. I need to establish what, if any, contiguous block of time of a minimum length (different per venue) exist on each day. For example, on 6/1 I have an event between 2:00pm and 7:00pm. The minimum time is 5 hours, so there's a block open there from 9am - 2pm and another between 7pm and 12pm. This would continue for the 2nd, 3rd, etc... every day of June. Some (most) of the days have nothing happening at all, some have 1 - 3 events. The solution I came up with works, but it also takes waaaay too long to generate the data. Basically, I loop every day of the month and create an array of timestamps for each 15 minutes of that day. Then, I loop the time spans of events from that day by 15 minutes, marking any "taken" timeslot as false. Remaining, I have an array that contains timestamp of free time vs. taken time: //one day's array after processing through loops (not real timestamps) array( 12345678=>12345678, // <--- avail 12345878=>12345878, 12346078=>12346078, 12346278=>false, // <--- not avail 12346478=>false, 12346678=>false, 12346878=>false, 12347078=>12347078, // <--- avail 12347278=>12347278 ) Now I would need to loop THIS array to find continuous time blocks, then check to see if they are long enough (each venue has a minimum), and if so then establish the descriptive text for their start and end (i.e. 9am - 2pm). WHEW! By the time all this looping is done, the user has grown bored and wandered off to Youtube to watch videos of puppies; it takes ages to so examine 30 or so days. Is there a faster way to solve this issue? To summarize the problem, given time ranges t1 and t2 on day d, how can I determine the remaining time left in d that is longer than the minimum time block m. This data is assembled on demand via AJAX as the user moves between calendar months. Results are cached per-page-load, so if the user goes to July a second time, the data that was generated the first time would be reused. Any other details that would help, let me know. Edit Per request, the database structure (or the part that is relevant here) *events* id (bigint) title (varchar) *event_times* id (bigint) event_id (bigint) venue_id (bigint) start (bigint) end (bigint) *venues* id (bigint) name (varchar) min_block (int) min_start (varchar) max_start (varchar)

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  • Looking for a function that will split profits/loss equally between 2 business partners.

    - by Hamish Grubijan
    This is not homework, for I am not a student. This is for my general curiosity. I apologize if I am reinventing the wheel here.The function I seek can be defined as follows (language agnostic): int getPercentageOfA(double moneyA, double workA, double moneyB, double workB) { // Perhaps you may assume that workA == 0 // Compute result return result; } Suppose Alice and Bob want to do business together ... such as ... selling used books. Alice is only interested in investing money in it and nothing else. Bob might invest some money, but he might have no $ available to invest. He will, however, put in the effort in finding a seller, a buyer, and doing maintenance. There are no tools, education, health insurance costs, or other expenses to consider. Both Alice and Bob wish to split the profits "equally" (A different weight like 40/60 for advanced users). Both are entrepreneurs, so they deal with low ROI/wage, and high income alike. There is no fixed wage, minimum wage, fixed ROI, or minimum ROI. They try to find the best deal possible, assume risks and go for it. Now, let's stick with the 50/50 model. If Alice invests $100, Bob invests work, and they will end up with a profit (or loss) of $60, they will split it equally - either both get $30 for their efforts/investments, or Bob ends up owing $30 to Alice. A second possibility: Both Alice and Bob invest 100, then Bob does all the work, and they end up splitting $60 profit. It looks like Alice should get only $15, because $30 of that profit came from Bob's investment and Bob's effort, so Alice shall have none of it, and the other $30 is to be split 50/50. Both of the examples above are trivial even when A and B want to split it 35/65 or what have you. Now it gets more complicated: What if Alice invests $70, and Bob invests $30 + does all of the work. It appears simple: (70,30) = (30,30) + (40,0) ... but, if only we knew how to weigh the two parts relative to each other. Another complicated (I think) example: what if Alice and Bob invest $70 and $30 respectively, and also put in an equal amount of work? I have a few data points: When A and B put in the same amount of work and the same $ - 50/50. When A puts in 100% of the money, and B does 100% of the work - 50/50. When A does all of the work and puts in all of the money - 100 for A / 0 for B (and vice-versa). When A puts in 50% of the money, and B puts in 50% of the money as well as does all of the work - 25 for A, and 75 for B (and vice-versa). If I fix things such that always workA = 0%, workB = 100% of the total work, then getPercentageOfA becomes a function: height z given x and y. The question is - how do you extrapolate this function between these several points? What is this function? If you can cover the cases when workA does not have to be 0% of the total work, and when investment vs work is split as 85/15 or using some other model, then what would the new function be?

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