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  • Algorithm to generate a crossword

    - by nickf
    Given a list of words, how would you go about arranging them into a crossword grid? It wouldn't have to be like a "proper" crossword puzzle which is symmetrical or anything like that: basically just output a starting position and direction for each word.

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  • Static analysis of multiple if statements (conditions)

    - by koppernickus
    I have code similar to: if conditionA(x, y, z) then doA() else if conditionB(x, y, z) then doB() ... else if conditionZ(x, y, z) then doZ() else throw ShouldNeverHappenException I would like to validate two things (using static analysis): If all conditions conditionA, conditionB, ..., conditionZ are mutually exclusive (i.e. it is not possible that two or more conditions are true in the same time). All possible cases are covered, i.e. "else throw" statement will never be called. Could you recommend me a tool and/or a way I could (easily) do this? I would appreciate more detailed informations than "use Prolog" or "use Mathematica"... ;-)

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  • Is currying just a way to avoid inheritance?

    - by Alex Mcp
    So my understanding of currying (based on SO questions) is that it lets you partially set parameters of a function and return a "truncated" function as a result. If you have a big hairy function takes 10 parameters and looks like function (location, type, gender, jumpShot%, SSN, vegetarian, salary) { //weird stuff } and you want a "subset" function that will let you deal with presets for all but the jumpShot%, shouldn't you just break out a class that inherits from the original function? I suppose what I'm looking for is a use case for this pattern. Thanks!

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  • How is dynamic memory allocation handled when extreme reliability is required?

    - by sharptooth
    Looks like dynamic memory allocation without garbage collection is a way to disaster. Dangling pointers there, memory leaks here. Very easy to plant an error that is sometimes hard to find and that has severe consequences. How are these problems addressed when mission-critical programs are written? I mean if I write a program that controls a spaceship like Voyager 1 that has to run for years and leave a smallest leak that leak can accumulate and halt the program sooner or later and when that happens it translates into epic fail. How is dynamic memory allocation handled when a program needs to be extremely reliable?

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  • What is a good standard exercise to learn the OO features of a language?

    - by FarmBoy
    When I'm learning a new language, I often program some mathematical functions to get used to the control flow syntax. After that, I like to implement some sorting algorithms to get used to the array/list constructs. But I don't have a standard exercise for exploring the languages OO features. Does anyone have a stock exercise for this? A good answer would naturally lend to inheritance, polymorphism, etc., for a programmer already comfortable with these concepts. An ideal answer would be one that could be communicated in a few words, without ambiguity, in the way that "implement mergesort" is completely unambiguous. (As an example, answering "design a game" is so vague as to be useless.) Any ideas? EDIT: I have to remark that the results here are somewhat ironic. 10 upvotes and (originally) 5 favorites suggest that this is a question others are interested in. Yet the most upvoted answer is one that says there is no good answer. Oh well. I think I'll look at the textbook below, I've found games useful in the past for OO.

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  • Looking for examples of "real" uses of continuations

    - by Sébastien RoccaSerra
    I'm trying to grasp the concept of continuations and I found several small teaching examples like this one from the Wikipedia article: (define the-continuation #f) (define (test) (let ((i 0)) ; call/cc calls its first function argument, passing ; a continuation variable representing this point in ; the program as the argument to that function. ; ; In this case, the function argument assigns that ; continuation to the variable the-continuation. ; (call/cc (lambda (k) (set! the-continuation k))) ; ; The next time the-continuation is called, we start here. (set! i (+ i 1)) i)) I understand what this little function does, but I can't see any obvious application of it. While I don't expect to use continuations all over my code anytime soon, I wish I knew a few cases where they can be appropriate. So I'm looking for more explicitely usefull code samples of what continuations can offer me as a programmer. Cheers!

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  • Need an algorithm to group several parameters of a person under the persons name

    - by QuickMist
    Hi. I have a bunch of names in alphabetical order with multiple instances of the same name all in alphabetical order so that the names are all grouped together. Beside each name, after a coma, I have a role that has been assigned to them, one name-role pair per line, something like whats shown below name1,role1 name1,role2 name1,role3 name1,role8 name2,role8 name2,role2 name2,role4 name3,role1 name4,role5 name4,role1 ... .. . I am looking for an algorithm to take the above .csv file as input create an output .csv file in the following format name1,role1,role2,role3,role8 name2,role8,role2,role4 name3,role1 name4,role5,role1 ... .. . So basically I want each name to appear only once and then the roles to be printed in csv format next to the names for all names and roles in the input file. The algorithm should be language independent. I would appreciate it if it does NOT use OOP principles :-) I am a newbie.

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  • Any Open Source Pregel like framework for distributed processing of large Graphs?

    - by Akshay Bhat
    Google has described a novel framework for distributed processing on Massive Graphs. http://portal.acm.org/citation.cfm?id=1582716.1582723 I wanted to know if similar to Hadoop (Map-Reduce) are there any open source implementations of this framework? I am actually in process of writing a Pseudo distributed one using python and multiprocessing module and thus wanted to know if someone else has also tried implementing it. Since public information about this framework is extremely scarce. (A link above and a blog post at Google Research)

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  • What "already invented" algorithm did you invent?

    - by Guy
    In my question Insert Update stored proc on SQL Server I explained an efficient way of doing an insert/update - perhaps THE most efficient. It's nothing amazing but it's a small algorithm that I came up with in a mini-Eureka moment. Although I had "invented" it by myself and secretly hoped that I was the first to do so I knew that it had probably been around for years but after posting on a couple of lists and not getting confirmation I had never found anything definitive written up about it. So my questions: What software algorithm did you come up with that you thought that you'd invented? Or better yet, did you invent one?

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  • Graph Algorithm To Find All Paths Between N Arbitrary Vertices

    - by russtbarnacle
    I have an graph with the following attributes: Undirected Not weighted Each vertex has a minimum of 2 and maximum of 6 edges connected to it. Vertex count will be < 100 I'm looking for paths between a random subset of the vertices (at least 2). The paths should simple paths that only go through any vertex once. My end goal is to have a set of routes so that you can start at one of the subset vertices and reach any of the other subset vertices. Its not necessary to pass through all the subset nodes when following a route. All of the algorithms I've found (Dijkstra,Depth first search etc.) seem to be dealing with paths between two vertices and shortest paths. Is there a known algorithm that will give me all the paths (I suppose these are subgraphs) that connect these subset of vertices?

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  • Any software for pattern-matching and -rewriting source code?

    - by Steven A. Lowe
    I have some old software (in a language that's not dead but is dead to me ;-)) that implements a basic pattern-matching and -rewriting system for source code. I am considering resurrecting this code, translating it into a modern language, and open-sourcing the project as a refactoring power-tool. Before I go much further, I want to know if anything like this exists already (my google-fu is fanning air on this tonight). Here's how it works: the pattern-matching part matches source-code patterns spanning multiple lines of code using a template with binding variables, the pattern-rewriting part uses a template to rewrite the matched code, inserting the contents of the bound variables from the matching template matching and rewriting templates are associated (1:1) by a simple (unconditional) rewrite rule the software operates on the abstract syntax tree (AST) of the input application, and outputs a modified AST which can then be regenerated into new source code for example, suppose we find a bunch of while-loops that really should be for-loops. The following template will match the while-loop pattern: Template oldLoopPtrn int @cnt@ = 0; while (@cnt@ < @max@) { … @body@ ++@cnt@; } End_Template while the following template will specify the output rewrite pattern: Template newLoopPtrn for(int @cnt@ = 0; @cnt@ < @max@; @cnt@++) { @body@ } End_Template and a simple rule to associate them Rule oldLoopPtrn --> newLoopPtrn so code that looks like this int i=0; while(i<arrlen) { printf("element %d: %f\n",i,arr[i]); ++i; } gets automatically rewritten to look like this for(int i = 0; i < arrlen; i++) { printf("element %d: %f\n",i,arr[i]); } The closest thing I've seen like this is some of the code-refactoring tools, but they seem to be geared towards interactive rewriting of selected snippets, not wholesale automated changes. I believe that this kind of tool could supercharge refactoring, and would work on multiple languages (even HTML/CSS). I also believe that converting and polishing the code base would be a huge project that I simply cannot do alone in any reasonable amount of time. So, anything like this out there already? If not, any obvious features (besides rewrite-rule conditions) to consider? EDIT: The one feature of this system that I like very much is that the template patterns are fairly obvious and easy to read because they're written in the same language as the target source code, not in some esoteric mutated regex/BNF format.

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  • To Throw or Not to Throw

    - by serhio
    // To Throw void PrintType(object obj) { if(obj == null) { throw new ArgumentNullException("obj") } Console.WriteLine(obj.GetType().Name); } // Not to Throw void PrintType(object obj) { if(obj != null) { Console.WriteLine(obj.GetType().Name); } } What principle to keep? Personally Personally I prefer the first one its say developer-friendly. The second one its say user-friendly. What do you think?

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  • Code Golf: Easter Spiral

    - by friol
    What's more appropriate than a Spiral for Easter Code Golf sessions? Well, I guess almost anything. The Challenge The shortest code by character count to display a nice ASCII Spiral made of asterisks ('*'). Input is a single number, R, that will be the x-size of the Spiral. The other dimension (y) is always R-2. The program can assume R to be always odd and = 5. Some examples: Input 7 Output ******* * * * *** * * * * ***** * Input 9 Output ********* * * * ***** * * * * * * *** * * * * * ******* * Input 11 Output *********** * * * ******* * * * * * * * *** * * * * * * * * ***** * * * * * ********* * Code count includes input/output (i.e., full program). Any language is permitted. My easily beatable 303 chars long Python example: import sys; d=int(sys.argv[1]); a=[d*[' '] for i in range(d-2)]; r=[0,-1,0,1]; x=d-1;y=x-2;z=0;pz=d-2;v=2; while d>2: while v>0: while pz>0: a[y][x]='*'; pz-=1; if pz>0: x+=r[z]; y+=r[(z+1)%4]; z=(z+1)%4; pz=d; v-=1; v=2;d-=2;pz=d; for w in a: print ''.join(w); Now, enter the Spiral...

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  • What is technically more advanced: Python or Assembler? [closed]

    - by el ka es
    I wondered which of these languages is more powerful. With powerful I don't mean the readability, assembler would be naturally the winner here, but something resulting from, for example, the following factors: Which of them is more high-level? (Both aren't really but one has to be more) Who would be the possibly fastest in compiled state? (There is no Python compiler out there as far as I know but it wouldn't be hard writing one I suppose) Which of the both has the better code length/code action ratio? What I mean is If you get to distracted by the, compared to Python, improved readability of assembler, just think of writing plain binary/machine code as what assembler assembles to. Both languages are so basic that it should be possible to answer the question(s) in a rather objective view, I hope.

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  • Good implementations of reinforced learning?

    - by Paperino
    For an ai-class project I need to implement a reinforcement learning algorithm which beats a simple game of tetris. The game is written in Java and we have the source code. I know the basics of reinforcement learning theory but was wondering if anyone in the SO community had hands on experience with this type of thing. What would your recommended readings be for an implementation of reinforced learning in a tetris game? Are there any good open source projects that accomplish similar things that would be worth checking out? Thanks in advanced Edit: The more specific the better, but general resources about the subject are welcomed. Follow up: Thought it would be nice if I posted a followup. Here's the solution (code and writeup) I ended up with for any future students :). Paper / Code

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  • Programming Technique: How to create a simple card game

    - by Shyam
    Hi, As I am learning the Ruby language, I am getting closer to actual programming. So I was thinking of creating a simple card game. My question isn't Ruby orientated, but I do know want to learn how to solve this problem with a genuine OOP approach. In my card game I want to have four players. Using a standard deck with 52 cards, no jokers/wildcards. In the game I won't use the Ace as a dual card, it is always the highest card. So, the programming problems I wonder about are the following: How can I sort/randomize the deck of cards? There are four types, each having 13 values. Eventually there can be only unique values, so picking random values could generate duplicates. How can I implement a simple AI? As there are tons of card games, someone would have figured this part out already, so references would be great. I am a truly Ruby nuby, and my goal here is to learn to solve problems, so pseudo code would be great, just to understand how to solve the problem programmatically. I apologize for my grammar and writing style if it's unclear, for it is not my native language. Also pointers to sites where such challenges are explained, would be a great resource! Thank you for your comments, answers and feedback!

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  • Encode complex number as RGB pixel

    - by Vi
    How is it better to encode a complex number into RGB pixel and vice versa? Probably (logarithm of) an absolute value goes to brightness and an argument goes to hue. Desaturated pixes should receive randomized argument in reverse transformation. Something like: 0 - (0,0,0) 1 - (255,0,0) -1 - (0,255,255) 0.5 - (128,0,0) i - (255,255,0) -i - (255,0,255) (0,0,0) - 0 (255,255,255) - e^(i * random) (128,128,128) - 0.5 * e^(i *random) (0,128,128) - -0.5 Are there ready-made formulas for that?

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  • How would you go about tackling this problem?

    - by incrediman
    I have a programming contest coming up in about half a week, and I've been prepping :) I found a bunch of questions from this canadian competition, they're great practice: http://cemc.math.uwaterloo.ca/contests/computing/2009/stage2/day1.pdf I'm looking at problem B ("Dinner"). Any idea where to start? I can't really think of anything besides the naive approach (ie. trying all permutations) which would take too long to be a valid answer. Btw, the language there says c++ and pascal I think, but i don't care what language you use - I mean really all I want is a brief description of how to tackle the problem. Like "use X technique treating each programmer as a Y" or something :)

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  • Do you still limit line length in code?

    - by Noldorin
    This is a matter on which I would like to gauge the opinion of the community: Do you still limit the length of lines of code to a fixed maximum? This was certainly a convention of the past for many languages; one would typically cap the number of characters per line to a value such as 80 (and more recnetly 100 or 120 I believe). As far as I understand, the primary reasons for limiting line length are: Readability - You don't have to scroll over horizontally when you want to see the end of some lines. Printing - Admittedly (at least in my experience), most code that you are working on does not get printed out on paper, but by limiting the number of characters you can insure that formatting doesn't get messed up when printed. Past editors (?) - Not sure about this one, but I suspect that at some point in the distant past of programming, (at least some) text editors may have been based on a fixed-width buffer. I'm sure there are points that I am still missing out, so feel free to add to these... Now, when I tend to observe C or C# code nowadays, I often see a number of different styles, the main ones being: Line length capped to 80, 100, or even 120 characters. As far as I understand, 80 is the traditional length, but the longer ones of 100 and 120 have appeared because of the widespread use of high resolutions and widescreen monitors nowadays. No line length capping at all. This tends to be pretty horrible to read, and I don't see it too often, though it's certainly not too rare either. Inconsistent capping of line length. The length of some lines are limited to a fixed maximum (or even a maximum that changes depending on the file/location in code), while others (possibly comments) are not at all. My personal preference here (at least recently) has been to cap the line length to 100 in the Visual Studio editor. This means that in a decently sized window (on a non-widescreen monitor), the ends of lines are still fully visible. I can however see a few disadvantages in this, especially when you end up writing code that's indented 3 or 4 levels and then having to include a long string literal - though I often take this as a sign to refactor my code! In particular, I am curious what the C and C# coders (or anyone who uses Visual Studio for that matter) think about this point, though I would be interested in hearing anyone's thoughts on the subject. Edit Thanks for the all answers - I appreciate the variety of opinions here, all presenting sound reasons. Consensus does seem to be tipping in the direction of always (or almost always) limit the line length. Interestingly, it seems to be in various coding standards to limit the line length. Judging by some of the answers, both the Python and Google CPP guidelines set the limit at 80 chars. I haven't seen anything similar regarding C# or VB.NET, but I would be curious to see if there are ones anywhere.

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