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  • Remove adjacent identical elements in a Ruby Array?

    - by Mike Woodhouse
    Ruby 1.8.6 I have an array containing numerical values. I want to reduce it such that sequences of the same value are reduced to a single instance of that value. So I want a = [1, 1, 1, 2, 2, 3, 3, 3, 3, 2, 2, 2, 3, 3, 3] to reduce to [1, 2, 3, 2, 3] As you can see, Array#uniq won't work in this case. I have the following, which works: (a.size - 1).downto(1) { |i| a[i] = nil if a[i - 1] == a[i] } Can anyone come up with something less ugly?

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  • Project Euler #163 understanding

    - by Paul
    I spent quite a long time searching for a solution to this problem. I drew tons of cross-hatched triangles, counted the triangles in simple cases, and searched for some sort of pattern. Unfortunately, I hit the wall. I'm pretty sure my programming/math skills did not meet the prereq for this problem. So I found a solution online in order to gain access to the forums. I didn't understand most of the methods at all, and some just seemed too complicated. Can anyone give me an understanding of this problem? One of the methods, found here: http://www.math.uni-bielefeld.de/~sillke/SEQUENCES/grid-triangles (Problem C) allowed for a single function to be used. How did they come up with that solution? At this point, I'd really just like to understand some of the concepts behind this interesting problem. I know looking up the solution was not part of the Euler spirit, but I'm fairly sure I would not have solved this problem anyhow.

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  • How to feed an xml database with tags obtained thru html forms ?

    - by blaise1
    Hello! Not a programmer, I begin with xml, html forms and xslt on Mac. I plan to use a form to post short texts in a xhtml page and invite end users to add some annotations to the said text. The users would select a specific part of the text posted and each annotation would stand for one specific chain of characters. My goal is to consolidate the tags obtained from various user's annotations to one xml "knowledge base" containing the original text with all the revision indicators. Then I plan to use xslt sheets to product various reports based on the tags obtained. my two questions are : 1- am I dreaming ? Is it really possible to do that with xml, xforms, xslt without using java, php, ajax or other seasoned programmer's tools ? 2- What should be my focus for further explorations aiming in that direction ? Which schema, events, sequences should I study ? Je vous remercie à l'avance, Please excuse my English. Blaise

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  • Time Complexities of recursive algorithms

    - by Peter
    Whenever I see a recursive solution, or I write recursive code for a problem, it is really difficult for me to figure out the time complexity, in most of the cases I just say its exponential? How is it exponential actually? How people say it is 2^n, when it is n!, when it is n^n or n^k. I have some questions in mind, let say find all permutations of a string (O(n!)) find all sequences which sum up to k in an array (exponential, how exactly do I calculate). Find all subsets of size k whose sum is 0 (will k come somewhere in complexity , it should come right?). Can any1 help me how to calculate the exact complexity of such questions, I am able to wrote code for them , but its hard understanding the exact time complexity.

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  • What is the representation of the mac command key in the terminal?

    - by freethinker
    Like control key is represented by a '^' in the terminal, what is the equivalent for the command key (mac)? I am trying to remap my bash shortcuts using stty For eg stty eof ^D But instead of control, I want to use the command key. EDIT: Okay so the issue I was trying to solve was that I wanted to interchange command and control keys because I work on osx and linux and the different key combinations cause me a lot of pain. So I interchanged the modifier keys using osx preferences. But now all the bash shortcuts like Ctrl+C etc had become equivalent of using the key sequences 'cmd+c' - which is not acceptable. Thankfully iTerm2, supports remapping of modifier keys as well, so for iterm2 I reversed them again which means iTerm2 recognizes command as command and control as control. So problem solved for now.

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  • How can I load an MP3 or similar music file for display and analysis in wxWidgets?

    - by Jon Cage
    I'm developing a GUI in wxPython which allows a user to generate sequences of colours for some toys I'm building. Part of the program needs to load an MP3 (and potentially other formats further down the line) and display it to the user. That should be sufficient to get started but later I'd like to add features like identifying beats and some crude frequency analysis. Is there any simple way of loading / understanding an MP3's contents to display a plot of its amplitudes to the screen using wxWidgets? I later intend to port to C++/wxWidgets for speed and to avoid having to distribute wxPython.

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  • byte-sized bit pattern in C and its relevance?

    - by Nikunj Banka
    I a reading Kerninghan and Ritchie's C programming language book and on page 37 it mentions byte sized bit patterns like : '\013' for vertical tab . '\007' for bell character . My doubts : What is byte sized in it and and what's a bit pattern ? What relevance does this hold and where can I apply it ? Is it in any sense related to escape sequences ? I can't seem to find any information what so ever about these byte sized bit patterns on the web . please help . thanks .

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  • Object-oriented Programming - need your help

    - by wanderameise
    hey folks, I try to realize a little game project to dive deeper into OO programming (winforms c++/cli). I already started coding but now I´d like to make a re-design. For the beginning the game should consist of four parts like game-engine, user interface, highscore and playground. Heres a little (non-UML-conform) class diagramm to visualize my purposes http://i.imgur.com/lmpwj.png Would this be the right way? In my eyes the game engine is responsible to control the game sequences (state machine?) and exchanges information betweens all other classes. I appreciate any help!

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  • Replacing elements within a string in R

    - by Maureen
    Hi, I have a row in a data frame in R that is made up of sequences of undetermined length of 0s 1s and 2s as characters. So "01", "010", "201", "102", "00012"... things like this. I'd like to find a way to determine if the last character in the string is NUMERICALLY the largest. It's important that I keep the row in the data frame as characters for other purposes. So basically I want to take substr(x, nchar(x), nchar(x)) and determine if it, as a number, is the largest of the numbers in the character string. I'm super lost as to how to do this, since I'm not all that familiar with regular expressions and I have to back and forth between treating elements as characters and numbers. Thanks in advance. ~Maureen

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  • PHP with SQL Injection

    - by Scott S
    For our first assignment in a System Security class, we have to hack into the professors "cheaply organized" sql database. I know the only user is "admin" and the select statement generated in the php is: select user_id from user where user_username = 'admin' AND user_password = md5('noob') I am having a number of problems attempting to bypass the password part of this statement as the professor has some javascript embedded in the page to sanitize the username and password of any non-alphanumeric values. This can be bypassed by turning off javascript :P but any values sent still get cleaned by the operating system (some build of Debian 32-bit). I've seen the code for the login request and it does not escape any characters. How do I bypass the operating systems escape sequences?

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  • bash: How to evaluate PS1, PS2, ...?

    - by Harry
    Is there any way to 'evaluate' PS1, PS2, etc from within a bash script? Although, I can use alternate means to get all elements of my current PS1, I would really like to be able to reuse its definition instead of using these alternate means. For example, ===================================== PS1 element --> Alternate means ===================================== \u --> $USER \h --> $HOSTNAME \w --> $PWD ... ===================================== I could very well use the 'alternate means' column in my script, but I don't want to. In my PS1, I, for example, use bold blue color via terminal escape sequences which I'd like to be able to simply reuse by evaluating PS1.

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  • Emulating a transaction-safe SEQUENCE in MySQL

    - by Michael Pliskin
    We're using MySQL with InnoDB storage engine and transactions a lot, and we've run into a problem: we need a nice way to emulate Oracle's SEQUENCEs in MySQL. The requirements are: - concurrency support - transaction safety - max performance (meaning minimizing locks and deadlocks) We don't care if some of the values won't be used, i.e. gaps in sequence are ok. There is an easy way to archieve that by creating a separate InnoDB table with a counter, however this means it will take part in transaction and will introduce locks and waiting. I am thinking to try a MyISAM table with manual locks, any other ideas or best practices?

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  • write cache and write sequence order

    - by excanoe
    ok, here i have some weird question: let say we have some binary file (.log), and sequence of write operations, for example log1, log2, log3 and each has some block size n (raw data). question: can I be sure that log1,log2 and log3 sequences can be written in the correct order in ONE file, even if i have few cache levels (disk hardware and os level)? update very interested in what will be with records order (not with records) if we have software or hardware failure (reboot or another reason). update there can be some percent of write failures, but main question is: will write order stay correct?

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  • Forking Multiple Apps Under Python Subprocess

    - by noxtion
    Hello all. I have been looking through Google and SO for something that could help me solve this but I have run into a block. I am a bit new to Python but I am looking for a way to run multiple apps that will continuously run in the background. For example, I need 4 apps to start up with a param -appnum set to a different value. I would like to use python to count up and then start up a new app that will continue to run. I assumed I would use subprocess but I feel a bit overwhelmed by the documentation. I also plan to have the app print out sequences of numbers and would like to redirect this to a file. I noticed some of the SO questions talked about this, but I am a little confused on what to do. -Mike

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  • How can I load an MP3 or similar music file for display and anaysis in wxWdigets?

    - by Jon Cage
    I'm developing a GUI in wxPython which allows a user to generate sequences of colours for some toys I'm building. Part of the program needs to load an MP3 (and potentially other formats further down the line) and display it to the user. That shuold be sufficient to get started but later I'd like to add features like identifying beats and some crude frequency analysis. Is there any simple way of loading / understanding an MP3's contents to display a plot of it's amplitudes to the screen using wxWidgets? I later intend to port to C++/wxWidgets for speed and to avoid having to distribute wxPython.

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  • What algorithm would you use to code a parrot?

    - by Phil H
    A parrot learns the most commonly uttered words and phrases in its vicinity so it can repeat them at inappropriate moments. So how would you create a software version? Assuming it has access to a microphone and can record sound at will, how would you code it without requiring infinite resources? The best I can imagine is to divide the stream using silences in the sound, and then use some pattern recognition to encode each one as a list of tokens, storing new ones as you meet them. Hashing the token sequences and counting occurrences in a database, you could build up a picture of the most frequently uttered phrases. But given the huge variety in phrases, how do you prevent this just becoming a huge list? And the sheer number of pairs to match would surely generate lot of false positives from the combinatorial nature of matching. Would you use a neural net, since that's how a real parrot manages it? Or is there another, cleverer way of matching large-scale patterns in analogue data?

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  • How to enter decimal/binary numbers when creating byte objects in python?

    - by Eric
    I'm using python 3.1.1. I know that I can create byte objects using the byte literal in the form of b'...'. In these byte objects, each byte can be represented as a character(in ascii code if I'm not wrong) or as a hexadecimal/octal number. Hexadecimal and octal numbers can be entered using an escape of \x for hexadecimal numbers and just a \ for octal numbers. However, there's no escape sequences for decimal or binary numbers. Is there any way to enter them into byte objects?

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  • OS X Terminal: Meta key + alt functionality at the same time

    - by abababa22
    Is there a way to use "alt/option" key as a meta key but still be able to use the key to make some characters which need it? For example in my local keyboard layout: @ is alt-2 \ is alt-shift-7 | is alt-7 etc. So if I set alt as meta key, I can't make those characters. On the other hand using "press esc, release esc, press a key" to make meta key sequences makes my hands hurt. Any emacs users with international keyboards who have solved this, please give any tips you might have! :) edit: It appears that I can set alt as meta key and then add these kind of settings in inputrc: "\e2": "@" This works in bash shell but it still won't work with emacs though, so no good.

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  • Count double palindromes in given int sequence

    - by jakubmal
    For a given int sequence check number of double palindromes, where by double palindrome we mean sequence of two same palindromes without break between them. So for example: in 1 0 1 1 0 1 we have 1 0 1 as a palindrome which appears 2 times without a break, in 1 0 1 5 1 0 1 we have 1 0 1 but it's separated (apart from the other palindromes in these sequences) Problem example test data is: 3 12 0 1 1 0 0 1 1 0 0 1 1 0 12 1 0 1 0 1 0 1 0 1 0 1 0 6 3 3 3 3 3 3 with answers 8 0 9 Manacher is obvious for the begging, but I'm not sure what to do next. Any ideas appreciated. Complexity should be below n^2 I guess. EDIT: int is here treated as single element of alphabet

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  • Should I convert overly-long UTF-8 strings to their shortest normal form?

    - by Grant McLean
    I've just been reworking my Encoding::FixLatin Perl module to handle overly-long UTF-8 byte sequences and convert them to the shortest normal form. My question is quite simply "is this a bad idea"? A number of sources (including this RFC) suggest that any over-long UTF-8 should be treated as an error and rejected. They caution against "naive implementations" and leave me with the impression that these things are inherently unsafe. Since the whole purpose of my module is to clean up messy data files with mixed encodings and convert them to nice clean utf8, this seems like just one more thing I can clean up so the application layer doesn't have to deal with it. My code does not concern itself with any semantic meaning the resulting characters might have, it simply converts them into a normalised form. Am I missing something. Is there a hidden danger I haven't considered?

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  • OneToMany association updates instead of insert

    - by Shvalb
    I have an entity with one-to-many association to child entity. The child entity has 2 columns as PK and one of the column is FK to the parent table. mapping looks like this: @OneToMany(cascade = {CascadeType.ALL}, fetch = FetchType.EAGER ) @JoinColumn(name="USER_RESULT_SEQUENCES.USER_RESULT_ID", referencedColumnName="USER_RESULT_ID", unique=true, insertable=true, updatable=false) private List<UserResultSequence> sequences; I create an instance of parent and add children instances to list and then try to save it to DB. If child table is empty it inserts all children and it works perfectly. if the child table is not empty it updates existing rows! I don't know why it updates instead of inserts, any ideas why this might happen?? Thank you!

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  • Error occurs while using SPADE method in R

    - by Yuwon Lee
    I'm currently mining sequence patterns using SPADE algorithm in R. SPADE is included in "arulesSequence" package of R. I'm running R on my CentOS 6.3 64bit. For an exercise, I've tried an example presented in http://en.wikibooks.org/wiki/Data_Mining_Algorithms_In_R/Sequence_Mining/SPADE When I tried to do "cspade(x, parameter = list(support = 0.4), control = list(verbose = TRUE))" R says: parameter specification: support : 0.4 maxsize : 10 maxlen : 10 algorithmic control: bfstype : FALSE verbose : TRUE summary : FALSE preprocessing ... 1 partition(s), 0 MB [0.096s] mining transactions ... 0 MB [0.066s] reading sequences ...Error in asMethod(object) : 's' is not an integer vector When I try to run SPADE on my Window 7 32bit, it runs well without any error. Does anybody know why such errors occur?

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  • dynamic memory allocation [closed]

    - by gcc
    i wanna write a program that creates (allocating memory) and manipulates (adding elements and increasing memory etc.) integer arrays dynamically according to given input sequences. input sequence which starts with the maximum number of arrays, includes integers to be put into arrays and some one letter characters which are commands to carry out some tasks (activating next array, deleting an array etc). also, i wanna create *c_arrays which is the address of the array whose elements are the actual capacities (How many integer slots are already allocated for an array?) of arrays how should i organize(set up) the algorithm?

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  • Removing control / special characters from log file

    - by digitalsky
    I have a log file captured by tclsh which captures all the backspace characters (ctrl-H, shows up as "^H") and color-setting sequences (eg. ^[[32m .... ^[[0m ). What is an efficient way to remove them? ^[...m This one is easy since, I can just do "sed -i /^[.*m//g" to remove them ^H Right now I have "sed -i s/.^H//", which "applies" a backspace, but I have to keep looping this until there are no more backspaces. while [ logfile == `grep -l ^H logfile` ]; do sed -i s/.^H// logfile ; done; "sed -i s/.^H//g" doesn't work because it would match consecutive backspaces. This process takes 11 mins for my log file with ~6k lines, which is too long. Any better ways to remove the backspace?

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  • Imperative Programming v/s Declarative Programming v/s Functional Programming

    - by kaleidoscope
    Imperative Programming :: Imperative programming is a programming paradigm that describes computation in terms of statements that change a program state. In much the same way as the imperative mood in natural languages expresses commands to take action, imperative programs define sequences of commands for the computer to perform. The focus is on what steps the computer should take rather than what the computer will do (ex. C, C++, Java). Declarative Programming :: Declarative programming is a programming paradigm that expresses the logic of a computation without describing its control flow. It attempts to minimize or eliminate side effects by describing what the program should accomplish, rather than describing how to go about accomplishing it. The focus is on what the computer should do rather than how it should do it (ex. SQL). A  C# example of declarative v/s. imperative programming is LINQ. With imperative programming, you tell the compiler what you want to happen, step by step. For example, let's start with this collection, and choose the odd numbers: List<int> collection = new List<int> { 1, 2, 3, 4, 5 }; With imperative programming, we'd step through this, and decide what we want: List<int> results = new List<int>(); foreach(var num in collection) {     if (num % 2 != 0)           results.Add(num); } Here’s what we are doing: *Create a result collection *Step through each number in the collection *Check the number, if it's odd, add it to the results With declarative programming, on the other hand, we write the code that describes what you want, but not necessarily how to get it var results = collection.Where( num => num % 2 != 0); Here, we're saying "Give us everything where it's odd", not "Step through the collection. Check this item, if it's odd, add it to a result collection." Functional Programming :: Functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions.Functional programming has its roots in the lambda calculus. It is a subset of declarative languages that has heavy focus on recursion. Functional programming can be a mind-bender, which is one reason why Lisp, Scheme, and Haskell have never really surpassed C, C++, Java and COBOL in commercial popularity. But there are benefits to the functional way. For one, if you can get the logic correct, functional programming requires orders of magnitude less code than imperative programming. That means fewer points of failure, less code to test, and a more productive (and, many would say, happier) programming life. As systems get bigger, this has become more and more important. To know more : http://stackoverflow.com/questions/602444/what-is-functional-declarative-and-imperative-programming http://msdn.microsoft.com/en-us/library/bb669144.aspx http://en.wikipedia.org/wiki/Imperative_programming   Technorati Tags: Ranjit,Imperative Programming,Declarative programming,Functional Programming

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