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  • Matching an IP address with an IP range?

    - by Legend
    I have a MySQL table setup as follows: +---------------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------------+-------------+------+-----+---------+----------------+ | ipaddress_s | varchar(15) | YES | MUL | NULL | | | ipaddress_e | varchar(16) | YES | | NULL | | +---------------+-------------+------+-----+---------+----------------+ where, ipaddress_s and ipaddress_e look something like: 4.100.159.0-4.100.159.255 Now is there a way I can actually get the row that contains a given IP address? For instance, given the IP address: "4.100.159.5", I want the above row to be returned. So I am trying for a query that looks something like this (but of course this is wrong because in the following I am considering IPs as strings): SELECT * FROM ranges WHERE ipaddress_s<"4.100.159.5" AND ipaddress_e>"4.100.159.5" Any suggestions?

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  • Determining when or when not to escape output

    - by Ygam
    I have a page, where I have approximately 90 items I need to output. Most of them are object properties (I am using ORM so these objects map to my database tables). But the question is, do I have to escape each of those 90 outputs by applying functions to each (in my case, the htmlspecialchars)? Wouldn't that add a bit of an overhead (calling a single function 90 times)?

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  • How can I lookup data about a book from its barcode number?

    - by Joel Spolsky
    I'm building the world's simplest library application. All I want to be able to do is scan in a book's UPC (barcode) using a typical scanner (which just types the numbers of the barcode into a field) and then use it to look up data about the book... at a minimum, title, author, year published, and either the Dewey Decimal or Library of Congress catalog number. The goal is to print out a tiny sticker ("spine label") with the card catalog number that I can stick on the spine of the book, and then I can sort the books by card catalog number on the shelves in our company library. That way books on similar subjects will tend to be near each other, for example, if you know you're looking for a book about accounting, all you have to do is find SOME book about accounting and you'll see the other half dozen that we have right next to it which makes it convenient to browse the library. There seem to be lots of web APIs to do this, including Amazon and the Library of Congress. But those are all extremely confusing to me. What I really just want is a single higher level function that takes a UPC barcode number and returns some basic data about the book.

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  • Why are there so many DB management Systems ?

    - by mr.bio
    Hi there , i always asked myself. Why are there so many DB management systems? I am not an DB expert and i never thought about using another DB than mysql. Programming languages offer different paradigms, so there it makes sense to choose a specific language for your purpose. What are factors to choose a specific DB management system ?

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  • If you use MVC in your web app then you dont need to use Smarty(TemplateEngine) Right?

    - by Imran
    I'm just trying to understand the Templating(system). If you use MVC in your web application then you don't need to use something like Smarty(template engine) as you are already separating application code from presentation code anyway by using MVC right? please correct me? So am i correct in thinking it's MVC OR Templating or do you use both in your apps?If any one could explain this in detail it would be great. Thank you in advance;-)

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  • Searching algorithmics: Parsing and processing a request

    - by James P.
    Say you were to create a search engine that can accept a query statement under the form of a String. The statement can be used to retrieve different types of objects with a given set of characteristics and possibly linked to other objects. In plain english or pseudo-code using an OOP approach, how would you go about parsing and processing statements as follows to get the series of desired objects ? get fruit with colour green get variety of apples, pears from Andy get strawberry with colour "deep red" and origin not Spain get total of sales of melons between 2010-10-10 and 2010-12-30 get last deliverydate of bananas from "Pete" and state not sold Hope the question is clear. If not I'll be more than happy to reformulate. P.S: This isn't homework ;)

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  • How are a session identifiers generated?

    - by Asaf R
    Most web applications depend on some kind of session with the user (for instance, to retain login status). The session id is kept as a cookie in the user's browser and sent with every request. To make it hard to guess the next user's session these session-ids need to be sparse and somewhat random. The also have to be unique. The question is - how to efficiently generate session ids that are sparse and unique? This question has a good answer for unique random numbers, but it seems not scalable for a large range of numbers, simply because the array will end up taking a lot of memory.

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  • What Use are Threads Outside of Parallel Problems on MultiCore Systesm?

    - by Robert S. Barnes
    Threads make the design, implementation and debugging of a program significantly more difficult. Yet many people seem to think that every task in a program that can be threaded should be threaded, even on a single core system. I can understand threading something like an MPEG2 decoder that's going to run on a multicore cpu ( which I've done ), but what can justify the significant development costs threading entails when you're talking about a single core system or even a multicore system if your task doesn't gain significant performance from a parallel implementation? Or more succinctly, what kinds of non-performance related problems justify threading? Edit Well I just ran across one instance that's not CPU limited but threads make a big difference: TCP, HTTP and the Multi-Threading Sweet Spot Multiple threads are pretty useful when trying to max out your bandwidth to another peer over a high latency network connection. Non-blocking I/O would use significantly less local CPU resources, but would be much more difficult to design and implement.

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  • routine to generate a 2d array from two 1d arrays and a function

    - by intuited
    I'm guessing that there's a word for this concept, and that it's available in at least some popular languages, but my perfunctory search was fruitless. A pseudocode example of what I'd like to do: function foo(a, b) { return a * b // EG } a = [ 1, 2, 3 ] b = [ 4, 5, 6 ] matrix = the_function_for_which_I_search(foo, [a, b] ) print matrix => [ [ 4, 8, 12], [5, 10, 15], [6, 12, 18] ] // or function concatenate(a,b) return a.b } print the_function_for_which_I_search( concatenate, [ a, b ]) => [ [ '14', '24', '34'], ['15', '25', '35'], [16', '26', '36'] ] In other words, function_for_which_I_search will apply the function given as its first argument to each combination of the elements of the two arrays passed as its second argument, and return the results as a two-dimensional array. I would like to know if such a routine has a common name, and if it's available in a python module, cpan package, ruby gem, pear package, etc. I'm also wondering if this is a core function in other languages, maybe haskell or R?

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  • Sort months ( with strings ) algorithm

    - by Oscar Reyes
    I have this months array: ["January", "March", "December" , "October" ] And I want to have it sorted like this: ["January", "March", "October", "December" ] I'm currently thinking in a "if/else" horrible cascade but I wonder if there is some other way to do this. The bad part is that I need to do this only with "string" ( that is, without using Date object or anything like that ) What would be a good approach?

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  • Language construct naming: Function/Goto

    - by sub
    How is a language construct with the following properties called? It has a beginning and an end, just like a function It has a header containing it's name, also like a function but without arguments There can be any number of statements between its beginning and end, like a function You can use a function to jump to its beginning from anywhere (even itself) and it will execute the statements contained in it until it reaches its end You can use a function to immediately stop the execution of its contents and jump back where it was called from The code it contains is in the same scope as everything else, so you can access all variables outside and create new ones which aren't deleted upon leaving the construct. All in all it is like a goto point with an end and the option to return where it was called from.

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  • Handling close-to-impossible collisions on should-be-unique values

    - by balpha
    There are many systems that depend on the uniqueness of some particular value. Anything that uses GUIDs comes to mind (eg. the Windows registry or other databases), but also things that create a hash from an object to identify it and thus need this hash to be unique. A hash table usually doesn't mind if two objects have the same hash because the hashing is just used to break down the objects into categories, so that on lookup, not all objects in the table, but only those objects in the same category (bucket) have to be compared for identity to the searched object. Other implementations however (seem to) depend on the uniqueness. My example (that's what lead me to asking this) is Mercurial's revision IDs. An entry on the Mercurial mailing list correctly states The odds of the changeset hash colliding by accident in your first billion commits is basically zero. But we will notice if it happens. And you'll get to be famous as the guy who broke SHA1 by accident. But even the tiniest probability doesn't mean impossible. Now, I don't want an explanation of why it's totally okay to rely on the uniqueness (this has been discussed here for example). This is very clear to me. Rather, I'd like to know (maybe by means of examples from your own work): Are there any best practices as to covering these improbable cases anyway? Should they be ignored, because it's more likely that particularly strong solar winds lead to faulty hard disk reads? Should they at least be tested for, if only to fail with a "I give up, you have done the impossible" message to the user? Or should even these cases get handled gracefully? For me, especially the following are interesting, although they are somewhat touchy-feely: If you don't handle these cases, what do you do against gut feelings that don't listen to probabilities? If you do handle them, how do you justify this work (to yourself and others), considering there are more probable cases you don't handle, like a supernonva?

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  • Is there anyone out there that codes like me?

    - by Jacob Relkin
    Hi, Some people have told me that my coding style is a lot different than theirs. I think I am somewhat neurotic when it comes to spacing and indenting though. Here's a snippet to show you what I mean: - ( void ) applicationDidFinishLaunching: ( UIApplication *) application { SomeObject *object = [ [ SomeObject alloc ] init ]; int x = 100 / 5; object.someInstanceVariable = ( ( 4 * x ) + rand() ); [ object someMethod ]; } Notice how I space out all of my brackets/parentheses, start curly braces on the same line, "my code has room to breathe", so to speak. So my questions are a) is this normal and b) What's your coding style?

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  • How does the verbosity of identifiers affect the performance of a programmer?

    - by DR
    I always wondered: Are there any hard facts which would indicate that either shorter or longer identifiers are better? Example: clrscr() opposed to ClearScreen() Short identifiers should be faster to read because there are fewer characters but longer identifiers often better resemble natural language and therefore also should be faster to read. Are there other aspects which suggest either a short or a verbose style? EDIT: Just to clarify: I didn't ask: "What would you do in this case?". I asked for reasons to prefer one over the other, i.e. this is not a poll question. Please, if you can, add some reason on why one would prefer one style over the other.

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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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  • simplify expression k/m%n

    - by aaa
    hello. Simple question, is it possible to simplify (or replace division or modulo by less-expensive operation) (k/m)%n where variables are integers and operators are C style division and modulo operators. what about the case where m and n are constants (both or just one), not based 2? Thank you

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  • How to program simple chat bot AI?

    - by Larsenal
    I want to build a bot that asks someone a few simple questions and branches based on the answer. I realize parsing meaning from the human responses will be challenging, but how do you setup the program to deal with the "state" of the conversation? EDIT: It will be a one-to-one conversation between a human and the bot.

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  • How to implement square root and exponentiation on arbitrary length numbers?

    - by tomp
    I'm working on new data type for arbitrary length numbers (only non-negative integers) and I got stuck at implementing square root and exponentiation functions (only for natural exponents). Please help. I store the arbitrary length number as a string, so all operations are made char by char. Please don't include advices to use different (existing) library or other way to store the number than string. It's meant to be a programming exercise, not a real-world application, so optimization and performance are not so necessary. If you include code in your answer, I would prefer it to be in either pseudo-code or in C++. The important thing is the algorithm, not the implementation itself. Thanks for the help.

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  • Bit Flipping in Hex

    - by freyrs
    I have an 8 digit hexadecimal number of which I need certain digits to be either 0 or f. Given the specific place of the digits is there a quick way to generate the hex number with those places "flipped" to f. For example: flip_digits(1) = 0x000000f flip_digits(1,2,4) = 0x0000f0ff flip_digits(1,7,8) = 0xff00000f I'm doing this on an embedded device so I can't call any math libraries, I suspect it can be done with just bit shifts but I can't quite figure out the method. Any sort of solution (Python, C, Pseudocode) will work. Thanks in advance.

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  • What are some good code optimization methods?

    - by esac
    I would like to understand good code optimization methods and methodology. How do I keep from doing premature optimization if I am thinking about performance already. How do I find the bottlenecks in my code? How do I make sure that over time my program does not become any slower? What are some common performance errors to avoid (e.g.; I know it is bad in some languages to return while inside the catch portion of a try{} catch{} block

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  • Can I change class types in a setter with an object-oriented language?

    - by user214626
    Hello, Here is the problem statement : Calling a setter on the object should result in the object to change to an object of a different class, which language can support this ? Ex. I have a class called "Man" (Parent Class), and two children namely "Toddler" and "Old Man", they are its children because they override a behaviour in Man called as walk.( i.e Toddler sometimes walks using both his hands and legs kneeled down and the Old man uses a stick to support himself). The Man class has a attribute called age, I have a setter on Man,say it is called setAge(int ageValue). I have 3 objects, 2 toddlers, 1 old-Man. (The system is up and running,i guess when we say objects it is obvious) .I will make this call, toddler.setAge(80), I expect the toddler to change to an object of type Old Man. Is this possible.Please suggest. Thanks,

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  • Is it advisable to have non-ascii characters in the URL?

    - by Ravi Gummadi
    We are currently working on a I18N project. I was just wondering what are the complications of having the non-ascii characters in the URL. If its not, what are the alternatives to deal with this problem? EDIT (in response to Maxym's answer): The site is going to be local to specific country and I need not worry about the world wide public accessing this site. I understand that from usability point of view, It is really annoying. What are the other technical problem associated with this?

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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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  • How to handle printing of HTML pages?

    - by Jaran
    In my portfolio site I have listed my projects under separate tabs (tab menu). This works well except for printing which requires the user to click on a tab, print, click on the next tab and print the same page again to get everything. Being a portfolio I'd assume that visitors want to print all of the content. Is there a general way to create a different style when printing a web page? Or should I just add a printer icon on my page which redirects the user to a different page where all the data is in a big chunk and then prompt the user's browser to start printing?

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