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  • How can I write simulations in Erlang?

    - by rick
    Hi guys, I want to do some numerical stuff in Erlang like this: You've got an array with the following values: [2,3,4] In each iteration, you calculate 0.1 * [n-1] + 0.7 *[n] + 0.2 * [n+1] This becomes the new [n]. If n == 0 then [n-1] = 0. If [n] == length of array then [n] = 0. So I try an example: [2,3,4] calculations: 0.1 * 0 + 0.7 * 2 + 0.2 * 3 = 2 0.1 * 2 + 0.7 * 3 + 0.2 * 4 = 3.1 0.1 * 3 + 0.7 * 4 + 0.2 * 0 = 3.1 So [2,3,4] becomes to [2, 3.1, 3.1] after one iteration. I know how to write this in a non-functional language like C. But I have difficulties to imagine, how this could be done in Erlang. I found some tutorials on how you read a file to a list. So this is not the problem. How can I spawn different Erlang processes that each process has one element of the list? How can I do calculations by communicating with 'the neighbors', so that the neighbors know where their neigbors are generically, without specifying each? How can I collect the data into a list? Eventually, is it possible to solve that problem in Erlang at all? Thanks for your help.

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  • Avoiding dependency injection

    - by dotnetdev
    When coding, I often come across the following pattern: -A method calls another method (Fine), but the method being called/callee takes parameters, so in the wrapping method, I pass in parameters. Problem is, this dependency carrying can go on and on. How could I avoid this (any sample code appreciated)? Thanks

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  • Challenging yourself as a programmer?

    - by Kevin
    We used to be a Coldfusion development shop before hopping over to PHP in 2008, now we primarily develop custom Drupal websites. I enjoyed going from CF to PHP, but I feel like I am getting a bit stale. I have been looking at different things like Ruby, Python, Obj C (iPhone). The problem is, there just isn't enough time in the day. What would be a fun new thing to learn that would refresh me a bit and challenge myself to learn more?

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  • Haskell: Why is it saying my function type is off?

    - by linkmaster03
    I wrote a little Haskell program to find the area of a triangle, primarily to practice custom types, but it keeps throwing the following error on compile: areafinder.hs:7:4: Couldn't match expected type 'Triangle' against inferred type 'm b' In a stmt of a 'do' expression: putStr "Base: " In the expression: do { putStr "Base: "; baseStr I'm not sure where 'm b' comes from, so I'm at a loss here. Why is it throwing this error, and what can I do to fix it? Here is my code: module Main where data Triangle = Triangle Double Double -- base, height getTriangle :: Triangle getTriangle = do putStr "Base: " baseStr Double calcTriangle (Triangle base height) = base * height main = putStrLn ("Area = " ++ show (calcTriangle getTriangle)) Thanks. :)

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  • Easy way to convert c code to assembly?

    - by Bob
    Is there an easy way (like a free program) that can covert c/c++ code to x86 assembly? I know that any c compiler does something very similar and that I can just compile the c code and then disassemble the complied executable, but that's kind of an overkill, all I want is to convert a few lines of code. Does anyone know of some program that can do that?

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  • HELP!! Implementing a search to match the specified author and displaying a book by the specified publisher

    - by Brian
    Hey guys! So i'm having problems with my assignment. I successfully got it to run multiple last names by the author, but now, I need to find all books by author, which means searching the collection for all books that match the specified author and I also need to find all books by publisher, which displays a list of books by the specified publisher. How would I implement this? Would I use string or vector? Any help will be much appreciated!

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  • List filtering: list comprehension vs. lambda + filter

    - by Agos
    I happened to find myself having a basic filtering need: I have a list and I have to filter it by an attribute of the items. My code looked like this: list = [i for i in list if i.attribute == value] But then i thought, wouldn't it be better to write it like this? filter(lambda x: x.attribute == value, list) It's more readable, and if needed for performance the lambda could be taken out to gain something. Question is: are there any caveats in using the second way? Any performance difference? Am I missing the Pythonic Way™ entirely and should do it in yet another way (such as using itemgetter instead of the lambda)? Thanks in advance

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  • Does a syntax for this exist? In any language?

    - by Michael
    It seems pretty common to me to have an argument, in a dynamically typed language that is either an Object or a key to lookup that object. For instance when I'm working with a database I might have a method getMyRelatedStuff(person) All I really need to lookup the related stuff is the id of the person so my method could look like this in python: def getMyRelatedStuff(person_or_id): id = person_or_id.id if isinstance(person,User) else person_or_id #do some lookup Or going the other direction: def someFileStuff(file_or_name): file = file_or_name if hasattr(file,'write') else open(file_or_name)

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  • Scala, make my loop more functional

    - by Pengin
    I'm trying to reduce the extent to which I write Scala (2.8) like Java. Here's a simplification of a problem I came across. Can you suggest improvements on my solutions that are "more functional"? Transform the map val inputMap = mutable.LinkedHashMap(1->'a',2->'a',3->'b',4->'z',5->'c') by discarding any entries with value 'z' and indexing the characters as they are encountered First try var outputMap = new mutable.HashMap[Char,Int]() var counter = 0 for(kvp <- inputMap){ val character = kvp._2 if(character !='z' && !outputMap.contains(character)){ outputMap += (character -> counter) counter += 1 } } Second try (not much better, but uses an immutable map and a 'foreach') var outputMap = new immutable.HashMap[Char,Int]() var counter = 0 inputMap.foreach{ case(number,character) => { if(character !='z' && !outputMap.contains(character)){ outputMap2 += (character -> counter) counter += 1 } } }

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  • how to configure IP cam to stream using right network card?

    - by robin hood
    I have IP cam that supports RTSP streaming. It's connected to router with 2 network cards with IP1 and IP2 addresses. I make 2 connections to IP cam by IP1 and IP2 addresses from the same IP and I need to receive corresponding streams thru correct network card, but both streams (RTP over UDP) go thru IP1. How this can be resolved? I don't know if RTSP server binds UDP sockets to corresponding IP and I don't know what IP stack is in IP cam (weak end system or strong end system). I haven't found anything interesting in router configuration. As I understand, routing table cannot help me cos I'm connected from the same IP, is it right? Also Sorry for incomplete info but it's all I have at the moment. Thanks for your time.

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  • Parallelism on two duo-core processor system

    - by Qin
    I wrote a Java program that draw the Mandelbrot image. To make it interesting, I divided the for loop that calculates the color of each pixel into 2 halves; each half will be executed as a thread thus parallelizing the task. On a two core one cpu system, the performance of using two thread approach vs just one main thread is nearly two fold. My question is on a two dual-core processor system, will the parallelized task be split among different processor instead of just utilize the two core on one processor? I suppose the former scenario will be slower than the latter one simply because the latency of communicating between 2 CPU over the motherboard wires. Any ideas? Thanks

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  • How to see "anti if" movement and its gaol?

    - by Vijay Shanker
    I have a developer for last 3 years, have been using if-else or if-else if statements a lot in my programing habit. And today, I found This link. One obvious sample i put here public void doSomthing(String target, String object){ //validate requests if(target != null && target.trim().length() < 1){ //invalid request; } //further logic } Now, I have seen this sort of check all over the places, libraries. So, I wanted to have a discussion about the worthiness of such a movement. Please let me know your views.

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  • Need a good website URL to test against

    - by Zombies
    I need a URL to just test basic http connectivity. It needs to be consistent and: Always be up Never change drastically due to IP or user agent. (IE: 301 Location redirect/ huge difference in content... minor would be tolerable) The URL itself has a consistent content-length. (IE: it doesn't vary from by 2kb at most, ever) A few examples, yet none match all 3 criteria: One example of always up: www.google.com (yet it 301 redirects based on IP location). Another good one is http://www.google.com/webhp?hl=en. but the problem there is that based on a given holiday, the content-length can really vary.

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  • how to set cache for css/js file.

    - by coderex
    Hi all, I have to use the cache for the css files and js file which i used in the site. my site running in a shared hosting server. nothing can be done with server. so what could be the solution for use cache and compression for js and css files.

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  • Directory name "cache" in IIS 5.

    - by Chuck Conway
    In IIS 5 one of the directories off the root has a leading underscore. All files under the directory are unreachable (404) from the browser. I have verified that the paths are correct. Other javascript files outside the directory comedown fine. Any thoughts? Example: http://fm74g4rndmu02.corp.com/_cache/softwarecommunity/api.js

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  • Low Throughput on Windows Named Pipe Over WAN

    - by MichaelB76
    I'm having problems with low performance using a Windows named pipe. The throughput drops off rapidly as the network latency increases. There is a roughly linear relationship between messages sent per second and round trip time. It seems that the client must ack each message before the server will send the next one. This leads to very poor performance, I can only send 5 (~100 byte) messages per second over a link with an RTT of 200 ms. The pipe is asynchronous, using multiple overlapped write operations (and multiple overlapped reads at the client end), but this is not improving throughput. Is it possible to send messages in parallel over a named pipe? The pipe is created using PIPE_TYPE_MESSAGE, would PIPE_READMODE_BYTE work better? Is there any other way I can improve performance? This is a deployed solution, so I can't simply replace the pipe with a socket connection (I've read that Windows named pipe aren't recommended for use over a WAN, and I'm wondering if this is why). I'd be grateful for any help with this matter.

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