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  • When does it make sense to use a map?

    - by kiwicptn
    I am trying to round up cases when it makes sense to use a map (set of key-value entries). So far I have two categories (see below). Assuming more exist, what are they? Please limit each answer to one unique category and put up an example. Property values (like a bean) age -> 30 sex -> male loc -> calgary Presence, with O(1) performance peter -> 1 john -> 1 paul -> 1

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  • MVP pattern. Presenter requires new view instance. Best practice

    - by Andrew Florko
    I try to apply MVP pattern for win.forms application. I have 2 forms: main & child. Main has a button and when you click it - child form should appear. There are 2 views interfaces that forms implement IMainView { event OnClick; ... } IChildView { ... } There are two presenters MainPresenter(IMainView) & ChildPresenter(IChildView) MainPresenter listens to OnClick event and then should create IChildView implementation. MainPresenter { ... MainClicked() { // it's required to create IChildView instance here } } How would you implement such creation typically? Shall IMainView has factory method for IChildView or may be it should be separate Views factory. What would you advise? Or maybe there is some misunderstanding of MVP here? Thank you in advance!

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  • Unsigneds in order to prevent negative numbers

    - by Bruno Brant
    let's rope I can make this non-sujective Here's the thing: Sometimes, on fixed-typed languages, I restrict input on methods and functions to positive numbers by using the unsigned types, like unsigned int or unsigned double, etc. Most libraries, however, doesn't seem to think that way. Take C# string.Length. It's a integer, even though it can never be negative. Same goes for C/C++: sqrt input is an int or a double. I know there are reasons for this ... for example your argument might be read from a file and (no idea why) you may prefer to send the value directly to the function and check for errors latter (or use a try-catch block). So, I'm assuming that libraries are way better designed than my own code. So what are the reasons against using unsigned numbers to represent positive numbers? It's because of overflow when we cast then back to signed types?

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  • Fast, Vectorizable method of taking floating point number modulus of special primes?

    - by caffiend
    Is there a fast method for taking the modulus of a floating point number? With integers, there are tricks for Mersenne primes, so that its possible to calculate y = x MOD 2^31 without needing division. Can any similar tricks be applied for floating point numbers? Preferably, in a way that can be converted into vector/SIMD operations, or moved into GPGPU code. The primes I'm interested in would be 2^7 and 2^31, although if there are more efficient ones for floating point numbers, those would be welcome.

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  • Serializing persistent/functional data structures

    - by Rob
    Persistent data structures depend on the sharing of structure for efficiency. For an example, see here. How can I preserve the structure sharing when I serialize the data structures and write them to a file or database? If I just naively traverse the datastructures, I'll store the correct values, but I'll lose the structure sharing. I'd like to be able to save data-structures with shared components to a file, restore them, and still have most of the structure shared in the restored data.

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  • Creating huge images

    - by David Rutten
    My program has the feature to export a hi-res image of the working canvas to the disk. Users will frequently try to export images of about 20,000 x 10,000 pixels @ 32bpp which equals about 800MB. Add that to the serious memory consumption already going on in your average 3D CAD program and you'll pretty much guarantee an out-of-memory crash on 32-bit platforms. So now I'm exporting tiles of 1000x1000 pixels which the user has to stitch together afterwards in a pixel editor. Is there a way I can solve this problem without the user doing any work? I figured I could probably write a small exe that gets command-lined into the process and performs the stitching automatically. It would be a separate process and it would thus have 2GB of ram all to itself. Or is there a better way still? I'd like to support jpg, png and bmp so writing the image as a bytestream to the disk is not really possible.

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  • Is there a website to lookup already common code functions?

    - by pinnacler
    I'm sitting here writing a function that I'm positive has been written before, somewhere on earth. It's just too common to have not been attempted, and I'm wondering why I can't just go to a website and search for a function that I can then copy and paste into my project in 2 seconds, instead of wasting my day reinventing the wheel. Sure there are certain libraries you can use, but where do you find these libraries and when they are absent, is there a site like I'm describing?

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  • Reusability, testability, code complexity reduction and showing-off-ability programming importance

    - by Andrew Florko
    There are lots of programming and architecture patterns. Patterns allow to make code cleaner, reusable, more testable & at last (but not at least) to feel the follower a real cool developer. How do you rank these considerations for you? What does affect you most when you decide to apply pattern? I wonder how many times code reusability (especially for MVP, MVC patterns) was important? For example DAL library often shared between projects (it's reusable) but how often controllers/views (abstracted via interfaces) are reused?

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  • What are CAD apps written in, and how are they organized ?

    - by ldigas
    What are CAD applications (Rhino, Autocad) of today written in and how are they organized internally ? I gave as an example, Autocad and Rhino, although I would love to hear of other examples as well. I'm particularly interested in knowing what is their backend written in (multilanguage ?) and how is it organized, and how do they handle their frontend (GUI) in real time ? Do they use native windows API's or some libraries of their own, since I imagine, as good as may be, the open source solutions on today's market won't cut it. I may be wrong ... As most of you who have used them know, they handle amongs other things relatively complex rotational operations in realtime (shading is not interesting me). I've been doing some experiments with several packages recently, and for some larger models found that there is considerable difference in speed in, for example, programed rotation (big full ship models) amongst some of them (which I won't name). So I'm wondering about their internals ... Also, if someone knows of some book on the subject, I'd be interested to hear of it.

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  • Is XML-RPC bad used as a protocol for a public API implementation?

    - by Jack Duluoz
    I need to implement a web API for a project I'm working on in this period. I read there are many standard protocols to do it: XML-RPC, SOAP, REST. Apparently, the XML-RPC one is the easiest one to implement and use from what I saw, but I didn't find anything about using it to implement an API. Instead I found many tutorial about creating a REST API in PHP, for example. Is there any counter-indication for using XML-RPC to implement a public web API? Also, more generally speaking, I could (sort of) define a custom protocol for my API, to keep things simpler (i.e. accepting only GET request containing the parameters I need): would this be so bad? Is using a standard protocol a must-do?

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  • when to make a method static

    - by Don
    Hi, I'd like to know how people decide whether to define a method as static. I'm aware that a method can only be defined as static if it doesn't require access to instance fields. So lets say we have a method that does not access instance fields, do you always define such a method as static, or only if you need to call it statically (without a reference to an instance). Perhaps another way of asking the same question, is whether you use static or non-static as the default? Thanks, Don

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  • What different terms mean the same thing (or don't, but people think they do)?

    - by Matthew Jones
    One of the pitfalls I run into on a daily basis is customers saying one thing while meaning another. Usually, this is just due to a miscommunication somewhere, but occasionally they are, in fact, saying the same thing I am just using a different term. For example, one of my customers the other day mentioned a feature he called, "find as you type." Being a little confused, I asked him what he meant, and he described the feature in Google where, once you start typing a search query, Google suggests other, popular queries that match the letters you have typed. Click! He meant AutoComplete! He was not wrong, it is just that I had never heard that term before. In the spirit of reducing confusion, what terms can you think of that are different but mean, essentially, the same thing? Also, what terms do people think mean the same thing, but don't. Please differentiate between the two. Please only one set of terms per answer, so we can vote on the best ones.

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  • Convince teammates to follow standards

    - by folone
    There's always one or two guys, who think, they are great programmers, and they don't need any literature/specifications/etc. They usually write awful code, that makes you want to hurt them. They catch and suppress Throwable's, return null's, concatenate String's in large loops, do other stupid stuff. So the question is — How do I make such a person follow best practices and specifications? He does not listen (cause he's the best programmer), team lead does not give a damn ("It actually works, so why changing it?.."), and I'm actually tired of rewriting that awful code on my own. What do I do? What would you do?

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  • Is it kEatSpeed or kSpeedEat?

    - by bobobobo
    I have a bunch of related constants that are not identical. What's the better way to name them? way #1 kWalkSpeed kRunSpeed kEatSpeed kDrinkSpeed Or, way #2 kSpeedWalk kSpeedRun kSpeedEat kSpeedDrink If we evaluate these based on readability understandability not bug prone with subtle errors due to using wrong variable name I think way #1 wins readability, they tie for understandability, and way #2 wins for not bug prone. I'm not sure how often it happens to others, but when variable names like this get long, then its easy to write kSpeedEatingWhenInAHurry when you really meant kSpeedEatingWhenInHome, especially when using autocomplete. Any perspectives?

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  • Are there any context-sensitive code search tools?

    - by Vicky
    I have been getting very frustrated recently in dealing with a massive bulk of legacy code which I am trying to get familiar with. Say I try to search for a particular function call, I get loads of results that turn out to be completely irrelevant; some of them are easy to spot, eg a comment saying // Fixed functionality in foo() so don't need to handle this here any more But others are much harder to spot manually, because they turn out to be calls from other functions in modules that are only compiled in certain cases, or are part of a much larger block of code that is #if 0'd out in its entirety. What I'd like would be a search tool that would allow me to search for a term and give me the choice to include or exclude commented out or #if 0'd out code. Then the search results would be displayed alongside a list of #defines that are required in order for that snippet of code to be relevant. I'm working in C / C++, but other than the specific comment syntax I guess the techniques should be more generally applicable. Does such a tool exist?

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  • Do similar passwords have similar hashes?

    - by SLC
    Our computer system at work requires users to change their password every few weeks, and you cannot have the same password as you had previously. It remembers something like 20 of your last passwords. I discovered most people simply increment a digit at the end of their password, so "thisismypassword1" becomes "thisismypassword2" then 3, 4, 5 etc. Since all of these passwords are stored somewhere, I wondered if there was any weakness in the hashes themselves, for standard hashing algorithms used to store passwords like MD5. Could a hacker increase their chances of brute-forcing the password if they have a list of hashes of similar passwords?

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  • Data clean up: are there libraries of common permutations that we can use? Or is there a better appr

    - by anyaelena
    We are working on clean-up and analysis of a lot of human-entered customer data. We need to decide programmatically whether 2 addresses (for example) are the same, even though the data was entered with slight variations. Right now we run each address through fairly simplistic string replacement (replacing avenue with ave, for example), concatenate the fields and compare the results. We are doing something similar with names. At the very least, it seems like our list of search-replace values should already exist somewhere. Or perhaps you can suggest a totally different and superior way to detect matches?

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  • what is the best algorithm to use for this problem

    - by slim
    Equilibrium index of a sequence is an index such that the sum of elements at lower indexes is equal to the sum of elements at higher indexes. For example, in a sequence A: A[0]=-7 A[1]=1 A[2]=5 A[3]=2 A[4]=-4 A[5]=3 A[6]=0 3 is an equilibrium index, because: A[0]+A[1]+A[2]=A[4]+A[5]+A[6] 6 is also an equilibrium index, because: A[0]+A[1]+A[2]+A[3]+A[4]+A[5]=0 (sum of zero elements is zero) 7 is not an equilibrium index, because it is not a valid index of sequence A. If you still have doubts, this is a precise definition: the integer k is an equilibrium index of a sequence if and only if and . Assume the sum of zero elements is equal zero. Write a function int equi(int[] A); that given a sequence, returns its equilibrium index (any) or -1 if no equilibrium indexes exist. Assume that the sequence may be very long.

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  • What is the fastest way to check if files are identical?

    - by ojblass
    If you have 1,000,0000 source files, you suspect they are all the same, and you want to compare them what is the current fasted method to compare those files? Assume they are Java files and platform where the comparison is done is not important. cksum is making me cry. When I mean identical I mean ALL identical. Update: I know about generating checksums. diff is laughable ... I want speed. Update: Don't get stuck on the fact they are source files. Pretend for example you took a million runs of a program with very regulated output. You want to prove all 1,000,000 versions of the output are the same. Update: read the number of blocks rather than bytes? Immediatly throw out those? Is that faster than finding the number of bytes? Update: Is this ANY different than the fastest way to compare two files?

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