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• Unique identifiers for users

  - by Christopher McCann

  If I have a table of a hundred users normally I would just set up an auto-increment userID column as the primary key. But if suddenly we have a million users or 5 million users then that becomes really difficult because I would want to start becoming more distributed in which case an auto-increment primary key would be useless as each node would be creating the same primary keys. Is the solution to this to use natural primary keys? I am having a real hard time thinking of a natural primary key for this bunch of users. The problem is they are all young people so they do not have national insurance numbers or any other unique identifier I can think of. I could create a multi-column primary key but there is still a chance, however miniscule of duplicates occurring. Does anyone know of a solution? Thanks

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• T-SQL Re-Assigning Order Numbering

  - by Meltdown

  Say I have a table with a field called "ordernum" that denotes the order of a given set of rows. Now imagine that I delete one of these rows. What type of query would work best for re-assigning the order numbers so that they remain sequential? Here's an example: id group_id name ordernum active --------------------------------------------------- 0_____0______'Name1'___5__true 1_____0______'Name2'___4__true 2_____0______'Name3'___3__true 3_____1______'Name4'___2__true 4_____1______'Name5'__1__true 5_____1______'Name6'__NULL___false Now if I deleted the column with id='4' how would I reset the values in the 'ordernum' field for that specific group? Is this even possible? Or if I added a new row. (The first time the rows are created they are sorted by date, but then the user has the option to set the order himself.) In my table design I have a column 'active' boolean. If 'active' is set to false, then 'ordernum' is set to NULL. Otherwise it should be given an order number.

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• Memory footprint of a parsed XML file in Classic ASP?

  - by Pete Duncanson

  Anyone know of a way to find out the amount of memory/size of a XMLDocument once it has parsed a XML file? I've been doing "beer mat" calculations so far but have been asked to come up with some more legit numbers through monitoring some how. I need to create about 1500 XML files (via FreeThreadedXMl-DOM object), which verge between 3-9K in size and store them in Application vars but our SysAdmin is worried about us gobbling up too much memory. Other than the crude method of booting up a fresh IIS instance and then loading everything in and monitoring before and after memory usage in Task Manager I can't think of a way of doing it with a bit more accuracy.

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• search & replace on 3000 row, 25 column spreadsheet

  - by Deca

  I'm attempting to clean up data in this (old) spreadsheet and need to remove things like single and double quotes, HTML tags and so on. Trouble is, it's a 3000 row file with 25 columns and every spreadsheet app I've tried (NeoOffice, MS Excel, Apple Numbers) chokes on it. Hard. Any ideas on how else I can clean this thing up for import to MySQL? Clearly I could go through each record manually, row by row, but would like to avoid that if at all possible. Likewise, I could write a PHP script to handle it on import, but don't want to put the server into a death spiral either.

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• Do I need to use decimal places when using floats? Is the "f" suffix necessary?

  - by Paulo Fierro

  I've seen several examples in books and around the web where they sometimes use decimal places when declaring float values even if they are whole numbers, and sometimes using an "f" suffix. Is this necessary? For example: [UIColor colorWithRed:0.8 green:0.914 blue:0.9 alpha:1.00]; How is this different from: [UIColor colorWithRed:0.8f green:0.914f blue:0.9f alpha:1.00f]; Does the trailing "f" mean anything special? Getting rid of the trailing zeros for the alpha value works too, so it becomes: [UIColor colorWithRed:0.8 green:0.914 blue:0.9 alpha:1]; So are the decimal zeros just there to remind myself and others that the value is a float? Just one of those things that has puzzled me so any clarification is welcome :)

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• C - floating point rounding

  - by hatorade

  I'm trying to understand how floating point numbers work. I think I'd like to test out what I know / need to learn by evaluating the following: I would like to find the smallest x such that x + 1 = x, where x is a floating point number. As I understand it, this would happen in the case where x is large enough so that x + 1 is closer to x than the next number higher than x representable by floating point. So intuitively it seems it would be the case where I don't have enough digits in the significand. Would this number x then be the number where the significand is all 1's. But then I can't seem to figure out what the exponent would have to be. Obviously it would have to be big (relative to 10^0, anyway).

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• Equivalent of LaTeX's \label and \ref in HTML.

  - by dreeves

  I have an FAQ in HTML (example) in which the questions refer to each other a lot. That means whenever we insert/delete/rearrange the questions, the numbering changes. LaTeX solves this very elegantly with \label and \ref -- you give items simple tags and LaTeX worries about converting to numbers in the final document. How do people deal with that in HTML? ADDED: Note that this is no problem if you don't have to actually refer to items by number, in which case you can set a tag with <a name="foo"> and then link to it with <a href="#foo">some non-numerical way to refer to foo</a>. But I'm assuming "foo" has some auto-generated number, say from an <ol> list, and I want to use that number to refer to and link to it.

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• How to code Fizzbuzz in F#

  - by Russell

  I am currently learning F# and have tried (an extremely) simple example of FizzBuzz. This is my initial attempt: for x in 1..100 do if x % 3 = 0 && x % 5 = 0 then printfn "FizzBuzz" elif x % 3 = 0 then printfn "Fizz" elif x % 5 = 0 then printfn "Buzz" else printfn "%d" x What solutions could be more elegant/simple/better (explaining why) using F# to solve this problem? Note: The FizzBuzz problem is going through the numbers 1 to 100 and every multiple of 3 prints Fizz, every multiple of 5 prints Buzz, every multiple of both 3 AND 5 prints FizzBuzz. Otherwise, simple the number is displayed. Thanks :)

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• math syntax checker written in python

  - by neurino

  All I need is to check, using python, if a string is a valid math expression or not. For simplicity let's say I just need + - * / operators (+ - as unary too) with numbers and nested parenthesis. I add also simple variable names for completeness. So I can test this way: test("-3 * (2 + 1)") #valid test("-3 * ") #NOT valid test("v1 + v2") #valid test("v2 - 2v") #NOT valid ("2v" not a valid variable name) I tried pyparsing but just trying the example: "simple algebraic expression parser, that performs +,-,*,/ and ^ arithmetic operations" I get passed invalid code and also trying to fix it I always get wrong syntaxes being parsed without raising Exceptions just try: >>>test('9', 9) 9 qwerty = 9.0 ['9'] => ['9'] >>>test('9 qwerty', 9) 9 qwerty = 9.0 ['9'] => ['9'] both test pass... o_O Any advice?

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• Compatibility issues with <a> and calling a function(); across different web browsers

  - by Matthew

  Hi, I am new to javascript. I wrote the following function rollDice() to produce 5 random numbers and display them. I use an anchor with click event to call the function. Problem is, in Chrome it won't display, works fine in IE, in firefox the 5 values display and then the original page w/anchor appears! I am suspicious that my script tag is too general but I am really lost. Also if there is a display function that doesn't clear the screen first that would be great. diceArray = new Array(5) function rollDice() { var i; for(i=0; i<5; i++) { diceArray[i]=Math.round(Math.random() * 6) % 6 + 1; document.write(diceArray[i]); } } when I click should display 5 rand variables

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• Validate a string in a table in SQL Server

  - by Ashish Gupta

  I need to check If a column value (string) in SQL server table starts with a small letter and can only contain '_', '-', numbers and alphabets. I know I can use a SQL server CLR function for that. However, I am trying to implement that validation using a scalar UDF and could make very little here...I can use 'NOT LIKE', but I am not sure how to make sure I validate the string irrespective of the order of characters or in other words write a pattern in SQL for this. Am I better off using a SQL CLR function? Any help will be appreciated.. Thanks in advance

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• Sorting array containing strings in objective c

  - by jakob

  Hello experts! I have an array named 'names' with strings looking like this: ["name_23_something", "name_25_something", "name_2_something"]; Now I would like to sort this array in ascending order so it looks like this: ["name_25_something", "name_23_something", "name_2_something"]; I guess that should start of with extracting the numbers since I want that the sorting is done by them: for(NSString *name in arr) { NSArray *nameSegments = [name componentsSeparatedByString:@"_"]; NSLog("number: %@", (NSString*)[nameSegments objectAtIndex:1]); } I'm thinking of creating a dictionary with the keys but I'm not sure if that is the correct objective-c way, maybe there some some methods I could use instead? Could you please me with some tips or example code how this sorting should be done in a proper way. Thank you

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• Compact a given array problem

  - by Bragaadeesh

  Dont know whether this is a duplicate, but this was an interview question asked to me. Given an array of random numbers and -1 placed inbetween, I have to compact the array meaning all the -1s are to be replaced and the final output should be the last valid index with the fresh array. For example. Input: 3 4 -1 -1 -1 5 8 -1 8 Output: 3 4 5 8 8 5 8 -1 8 and last valid index is 4 Input: -1 -1 -1 -1 -1 2 Output: 2 -1 -1 -1 -1 2 and last valid index is 0 Input: -1 -1 -1 3 3 3 Output: 3 3 3 3 3 3 and last valid index is 2 You should not swap the values just the last valid index along with the array is enough to decipher the non negative values.

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• How should I use random.jumpahead in Python

  - by Peter Smit

  I have a application that does a certain experiment 1000 times (multi-threaded, so that multiple experiments are done at the same time). Every experiment needs appr. 50.000 random.random() calls. What is the best approach to get this really random. I could copy a random object to every experiment and do than a jumpahead of 50.000 * expid. The documentation suggests that jumpahead(1) already scrambles the state, but is that really true? Or is there another way to do this in 'the best way'? (No, the random numbers are not used for security, but for a metropolis hasting algorithm. The only requirement is that the experiments are independent, not whether the random sequence is somehow predictable or so)

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• Overuse of guards in Erlang?

  - by dagda1

  Hi, I have the following function that takes a number like 5 and creates a list of all the numbers from 1 to that number so create(5). returns [1,2,3,4,5]. I have over used guards I think and was wondering if there is a better way to write the following: create(N) -> create(1, N). create(N,M) when N =:= M -> [N]; create(N,M) when N < M -> [N] ++ create(N + 1, M). Thanks, Paul

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• Easiest way to find the correct kademlia bucket

  - by Martin

  In the Kademlia protocol node IDs are 160 bit numbers. Nodes are stored in buckets, bucket 0 stores all the nodes which have the same ID as this node except for the very last bit, bucket 1 stores all the nodes which have the same ID as this node except for the last 2 bits, and so on for all 160 buckets. What's the fastest way to find which bucket I should put a new node into? I have my buckets simply stored in an array, and need a method like so: Bucket[] buckets; //array with 160 items public Bucket GetBucket(Int160 myId, Int160 otherId) { //some stuff goes here } The obvious approach is to work down from the most significant bit, comparing bit by bit until I find a difference, I'm hoping there is a better approach based around clever bit twiddling. Practical note: My Int160 is stored in a byte array with 20 items, solutions which work well with that kind of structure will be preferred.

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• Numeric comparison difficulty in R

  - by Matt Parker

  I'm trying to compare two numbers in R as a part of a if-statement condition: (a-b) >= 0.5 In this particular instance, a = 0.58 and b = 0.08... and yet (a-b) >= 0.5 is false. I'm aware of the dangers of using == for exact number comparisons, and this seems related: (a - b) == 0.5) is false, while all.equal((a - b), 0.5) is true. The only solution I can think of is to have two conditions: (a-b) > 0.5 | all.equal((a-b), 0.5). This works, but is that really the only solution? Should I just swear off of the = family of comparison operators forever?

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• Is there a way in Sphinx/Pygments to emphasize one or more lines of code in literal includes?

  - by Casey

  In some sphinx docs I am writing, I am including code samples from an ancillary file like so: .. literalinclude:: mymodule.py :pyobject: MyClass :linenos: This particular doc is a tutorial, where the classes are build up step by step. What I would like to do is include the entire class or a single method, and emphasize only the lines of interest to that section. That way the context is preserved but the interesting parts are obvious at a glance. Right now I have resorted to just referring to line numbers in the text, which is ok, but far from ideal. Looking at the docs and code for sphinx and pygments I don't find an obvious way to do this. I'm not opposed to patching them or doing something tricky in conf.py, but I wondered if anyone had solved this.

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• Monotone-increasing Version Number based on Mercurial Commits

  - by Isaac

  When I was using subversion for the code for an application, I could append a period and the result of svnversion to the version number to create a unique and monotone-increasing version number and also be guaranteed that any check-out of the same revision of the code would generate the same version number. In Mercurial, because revision numbers are not necessarily consistent across clones, the local revision number is not suitable. The hash is appropriately unique and consistent, but does not create a number that is monotone-increasing. How can I generate a suitable number to append to the version number based on the Mercurial repository commits?

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• Easiest way to pass a javascript array or its values to a servlet and convert to a HashMap

  - by Ankur

  I have a Javascript array. I want to pass it's data to a servlet using the ajax() method of jQuery. What is the easiest way to do this. The index values i.e. the i in array[i] are not in order, they are numbers that have meaning themselves, hence I cannot simply loop through and create a GET queryString, or so I believe. Maybe I should be converting the JavaScript array to a JSON Object and sending that to the server ?? I am stumped on this one.

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• Can an app use the clipboard for its own purposes? (read: who owns the clipboard?)

  - by eran

  In PowerBuilder's IDE, the code autocomplete feature uses the clipboard to communicate the completed text to the code window. By doing so, it overrides whatever was stored on the clipboard before. So, if you had the winning numbers of the next lottary stored on your clipboard, and you used the autocomplete to turn m_goodfor into m_goodfornothing, you've just lost your only chance of ever getting rich, and you're left with nothing on your clipboard. Features like that are the reason I hate software. It looks like it was implemented by some intern that noone was looking after. However, there's also a chance I got all worked up for nothing, and making such use of the clipboard is absolutely legit. So, can an app use the clipboard for its own purposes? Who is considered the owner of the clipboard? (Bonus votes to whoever puts himself in place of the feature's programmer, and provides some reasoning for this being done on purpose, assuming the users would actually benefite from it)

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• how to read an address in multiple formats like google maps

  - by ratan

  notice that on google maps you can input the address any way you like. as long as it is a valid address...google maps will read it. In some ruby book I had seen code snippet for something like this, but with phone numbers. Any ideas how this could be done for addresses? in language of your choice. EDIT: i dont care about a "valid" address. I just want to parse an address. so that 123 fake street, WA, 34223 would be an address and so will 123 fake street WA 34223

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• How can I set a counter column value in MySQL?

  - by Jon Tackabury

  I have a table with a "SortID" column that is numbered using consecutive numbers. Whenever a row is deleted, it leaves a gap. Is there a way using pure SQL to update the rows with their row number? Something like this: UPDATE tbl SET SortID={rowindex} ORDER BY SortID (I realize this isn't valid SQL, that's why I'm asking for help) This should set the first row to #1, the second row to #2... etc. Is this possible using SQL? Please forgive the poorly worded question, I'm not really sure the best way to ask this. :)

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• Computed properties in NHibernate

  - by Liron Levi

  I'm having a problem in mapping an existing data class member to the database.. I have a database table where one of the columns is a string type, but actually stores a comma separated list of numbers. My data class shows this field as a list of integers. The problem is that I couldn't find any hook in NHibernate that allows me to invoke the custom code that is required to replace the string field by the list and vice versa. To illustrate (simplified of course): The database table: CREATE TABLE dummy ( id serial, numlist text -- (can store values such as '1,2,3') ) The data class: class Dummy { public int Id; public List<int> NumbersList; } Can anyone help?

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• PHP urlize function

  - by Maxime

  Hello guys, I'm using this function on my website to transform user input into acceptable URL: function urlize($url) { $search = array('/[^a-z0-9]/', '/--+/', '/^-+/', '/-+$/' ); $replace = array( '-', '-', '', ''); return preg_replace($search, $replace, utf2ascii($url)); } function utf2ascii($string) { $iso88591 = "\\xE0\\xE1\\xE2\\xE3\\xE4\\xE5\\xE6\\xE7"; $iso88591 .= "\\xE8\\xE9\\xEA\\xEB\\xEC\\xED\\xEE\\xEF"; $iso88591 .= "\\xF0\\xF1\\xF2\\xF3\\xF4\\xF5\\xF6\\xF7"; $iso88591 .= "\\xF8\\xF9\\xFA\\xFB\\xFC\\xFD\\xFE\\xFF"; $ascii = "aaaaaaaceeeeiiiidnooooooouuuuyyy"; return strtr(mb_strtolower(utf8_decode($string), 'ISO-8859-1'),$iso88591,$ascii); } I'm having a problem with it though, with numbers. For some reason when I try: echo urlize("test 23342"); I get "test-eiioe". Why is that and how can I fix it? Thank you very much!

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