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  • compute mean in python for a generator

    - by nmaxwell
    Hi, I'm doing some statistics work, I have a (large) collection of random numbers to compute the mean of, I'd like to work with generators, because I just need to compute the mean, so I don't need to store the numbers. The problem is that numpy.mean breaks if you pass it a generator. I can write a simple function to do what I want, but I'm wondering if there's a proper, built-in way to do this? It would be nice if I could say "sum(values)/len(values)", but len doesn't work for genetators, and sum already consumed values. here's an example: import numpy def my_mean(values): n = 0 Sum = 0.0 try: while True: Sum += next(values) n += 1 except StopIteration: pass return float(Sum)/n X = [k for k in range(1,7)] Y = (k for k in range(1,7)) print numpy.mean(X) print my_mean(Y) these both give the same, correct, answer, buy my_mean doesn't work for lists, and numpy.mean doesn't work for generators. I really like the idea of working with generators, but details like this seem to spoil things. thanks for any help -nick

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  • Programming language for fast calculations with big integers

    - by sub
    I'm doing Project Euler problems at the moment and I can solve most of them using my own programming language which uses direct C++ integers (so they are bound to 2^32 on my machine). However, at times there are problems which require me to work with very high numbers, I can't do that with native integers. So I implemented a BigInt library in my language which unfortunately gets extremely slow at times. Is there a programming language suitable for very efficient handling of big numbers? I mean that I want to do the things I could do in other programming languages with it (variables, loops, etc.), but in a faster way. If you have got tips for workarounds of the 2^32 limit in my language/C++/other languages, please tell me too!

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  • Codeigniter: A nice straight forward tutorial on how to build a reset password/forgotten password?

    - by Psychonetics
    I've built a full sign up system with user account activation, login, validation, captcha etc. To complete this I now need to implement a forgot password/reset password feature.. I have created one function that generates a random password 8 characters, another method that takes that random password word and applies sha1 and hashing. Also one that takes that hashed password and stores it in a table in the database. I will keep these methods to one side as they might come in handy later on but for now I would like to know if anyone can point me to a nice tutorial for creating a password reset feature for my website. Thanks in advance

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  • How can I make my counter look less fake?

    - by Eddy Pronk
    I'm using this bit of code to display the number of users on a site. My customer is complaining it looks fake. Any suggestions? var visitors = 187584; var updateVisitors = function() { visitors++; var vs = visitors.toString(), i = Math.floor(vs.length / 3), l = vs.length % 3; while (i-->0) if (!(l==0&&i==0)) vs = vs.slice(0,i*3+l) + ',' + vs.slice(i*3+l); $('#count').text(vs); setTimeout(updateVisitors, Math.random()*2000); }; setTimeout(updateVisitors, Math.random()*2000);

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  • ordered list does not work on IE7 (<ol><li).

    - by Cesar Lopez
    Hi all, I am trying to create an ordered list on IE7 but for some reason does not work. Does anybody knows why this can be? Thanks. eg. <ol> <li></li> <li><li> <ol> Update As an example I saw this page where if you look at it on IE7 you wont see de numbers, but if you look at it on any other (but not ie) you will see the numbers. http://www.arraystudio.com/as-workshop/make-ol-list-start-from-number-different-than-1-using-css.html Thanks

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  • Coldfusion CFC creation taking a variable amout of time to execute.

    - by Bazza
    I've been doing some logging of object creation times in our open account process in production. Periodically, initializing an object would take way longer than expected. By initializing I mean calling it's init() and passing a couple of arguments that may be simple variables or objects. e.g. <cfset validateObj = createObject("component", "compExample").init( productionMode = VARIABLES.productionMode, ipWhiteListed = isWhiteListed, ipLocatorObj = VARIABLES.ipLocatorObj ) /> Thats all that happens in init() methods. Generally the execution time would be 0ms, but at random times I might get 3 or 3.5 seconds. This is not specific to one particular server or to our generally busy period. It appears to be quite random. One thought was that these templates were being evicted from our template cache as they are not especially frequently used, although I checked cfstat on a number of servers and the max CP/Sec is -1. Running CF 8,0,1 Has anybody else ever come across this?

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  • How to get a Javascript routine to NOT act if it's in a text box?

    - by talkingnews
    I've got a simple page, and in that page runs a simple jquery keypress routine to catch clicks of the numbers 1 to 9 (has to be that to pass RNIB accessibility test). And in that page is a form, which can have numbers entered as part of a postcode. http://find.talking-newspapers.co.uk/result.php?addressInput=kingston Scroll to the bottom, try typing 8 or 9 for example. The text is entered, but it also acts on the keypress. Expected, but not good. I'm aware of various things like document.getElementById, but I can't figure out how to put these together to ensure that while the cursor is in the text input box, it doesn't act out the keypress catcher.

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  • How to use traceit to report function input variables in stack trace

    - by reckoner
    Hi, I've been using the following code to trace the execution of my programs: import sys import linecache import random def traceit(frame, event, arg): if event == "line": lineno = frame.f_lineno filename = frame.f_globals["__file__"] if filename == "<stdin>": filename = "traceit.py" if (filename.endswith(".pyc") or filename.endswith(".pyo")): filename = filename[:-1] name = frame.f_globals["__name__"] line = linecache.getline(filename, lineno) print "%s:%s:%s: %s" % (name, lineno,frame.f_code.co_name , line.rstrip()) return traceit def main(): print "In main" for i in range(5): print i, random.randrange(0, 10) print "Done." sys.settrace(traceit) main() Using this code, or something like it, is it possible to report the values of certain function arguments? In other words, the above code tells me "which" functions were called and I would like to know "what" the corresponding values of the input variables for those function calls. Thanks in advance.

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  • Standard (cross-platform) way for bit manipulation

    - by Kiril Kirov
    As are are different binary representation of the numbers (for example, take big/little endian), is this cross-platform: some_unsigned_type variable = some_number; // set n-th bit, starting from 1, // right-to-left (least significant-to most significant) variable |= ( 1 << ( n - 1 ) ); // clear the same bit: variable &= ~( 1 << ( n - 1 ) ); In other words, does the compiler always take care of the different binary representation of the unsigned numbers, or it's platform-specific? And what if variable is signed integral type (for example, int) and its value is zero positive negative? What does the Standard say about this? P.S. And, yes, I'm interesting in both - C and C++, please don't tell me they are different languages, because I know this :) I can paste real example, if needed, but the post will become too long

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  • I'm having a problem identifying a floating point exception.

    - by Peter Stewart
    I'm using c++ in visual studio express to generate random expression trees for use in a genetic algorithm type of program. Because they are random, the trees often generate (I'll call them exceptions, I'm not sure what they are) Thanks to a suggestion by George, I turned the mask _MCW_EM on so that hardware interrupts are turned off. (the default) So, the program runs uninterrupted, but some of the values returned are: -1.#INF, -1.#NAN, -1.#INV. I don't know how to identify these so that I can throw an exeption: if ( variable == -1.#INF) ?? DigitalRoss in this post seemed to have the solution, but as I understood it I couldn't make it work. I've been looking all over the place for this simple bit of code, that I assumed would be used all the time, but have had no luck. thanks

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  • How do I get the median/mode/range of a column in SQL using Java?

    - by Derek
    I have to get the median, mode and range of test scores from one column in a table but I am unsure how to go about doing that. When you connect to the database using java, you are normally returned a ResultSet that you can make a table or something out of but how do you get particular numbers or digits? Is there an SQL command to get the median/mode/range or will I have to calculate this myself, and how do you pull out numbers from the table in order to be able to calculate the mode/median/range? Thanks.

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  • A good Sorted List for Java

    - by Phuong Nguyen de ManCity fan
    I'm looking for a good sorted list for java. Googling around give me some hints about using TreeSet/TreeMap. But these components is lack of one thing: random access to an element in the set. For example, I want to access nth element in the sorted set, but with TreeSet, I must iterate over other n-1 elements before I can get there. It would be a waste since I would have upto several thousands elements in my Set. Basically, I'm looking for some thing similar to a sorted list in .NET, with ability to add element fast, remove element fast, and have random access to any element in the list. Has this kind of sorted list implemented somewhere? Thanks.

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  • Effective Data Validation

    - by John Conde
    What's an effective way to handle data validation, say, from a form submission? Originally I had a bunch of if statements that checked each value and collected invalid values in an array for later retrieval (and listing). // Store errors here $errors = array(); // Hypothetical check if a string is alphanumeric if (!preg_match('/^[a-z\d]+$/i', $fieldvalue)) { $errors[$fieldname] = 'Please only use letters and numbers for your street address'; } // etc... What I did next was create a class that handles various data validation scenarios and store the results in an internal array. After data validation was complete I would check to see if any errors occurred and handle accordingly: class Validation { private $errorList = array(); public function isAlphaNumeric($string, $field, $msg = '') { if (!preg_match('/^[a-z\d]+$/i', $string)) { $this->errorList[$field] = $msg; } } // more methods here public function creditCard($cardNumber, $field, $msg = '') { // Validate credit card number } // more methods here public function hasErrors() { return count($this->errorList); } } /* Client code */ $validate = new Validation(); $validate->isAlphaNumeric($fieldvalue1, $fieldname1, 'Please only use letters and numbers for your street address'); $validate->creditCard($fieldvalue2, $fieldname2, 'Please enter a valid credit card number'); if ($validate->hasErrors()) { // Handle as appropriate } Naturally it didn't take long before this class became bloated with the virtually unlimited types of data to be validated. What I'm doing now is using decorators to separate the different types of data into their own classes and call them only when needed leaving generic validations (i.e. isAlphaNumeric()) in the base class: class Validation { private $errorList = array(); public function isAlphaNumeric($string, $field, $msg = '') { if (!preg_match('/^[a-z\d]+$/i', $string)) { $this->errorList[$field] = $msg; } } // more generic methods here public function setError($field, $msg = '') { $this->errorList[$field] = $msg; } public function hasErrors() { return count($this->errorList); } } class ValidationCreditCard { protected $validate; public function __construct(Validation $validate) { $this->validate = $validate; } public function creditCard($cardNumber, $field, $msg = '') { // Do validation // ... // if there is an error $this->validate->setError($field, $msg); } // more methods here } /* Client code */ $validate = new Validation(); $validate->isAlphaNumeric($fieldvalue, $fieldname, 'Please only use letters and numbers for your street address'); $validateCC = new ValidationCreditCard($validate); $validateCC->creditCard($fieldvalue2, $fieldname2, 'Please enter a valid credit card number'); if ($validate->hasErrors()) { // Handle as appropriate } Am I on the right track? Or did I just complicate data validation more then I needed to?

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  • Simple RSA encryption (Java)

    - by jake blue
    This is simply for fun. This will not be used for any actual encryption. I'm only first year comp sci student and love cryptography. This took a long time to get working. At approximately N = 18, it begins breaking down. It won't encrypt messages properly after that point. I'm not sure why. Any insights? I'd also appreciate any links you could provide me to tutorials or interesting reading about Cryptography. import java.math.BigInteger; import java.security.SecureRandom; /** * Cryptography. * * Generates public and private keys used in encryption and * decryption * */ public class RSA { private final static BigInteger one = new BigInteger("1"); private final static SecureRandom random = new SecureRandom(); // prime numbers private BigInteger p; private BigInteger q; // modulus private BigInteger n; // totient private BigInteger t; // public key private BigInteger e; // private key private BigInteger d; private String cipherText; /** * Constructor for objects of class RSA */ public RSA(int N) { p = BigInteger.probablePrime(N/2, random); q = BigInteger.probablePrime(N/2, random); // initialising modulus n = p.multiply(q); // initialising t by euclid's totient function (p-1)(q-1) t = (p.subtract(one)).multiply(q.subtract(one)); // initialising public key ~ 65537 is common public key e = new BigInteger("65537"); } public int generatePrivateKey() { d = e.modInverse(t); return d.intValue(); } public String encrypt(String plainText) { String encrypted = ""; int j = 0; for(int i = 0; i < plainText.length(); i++){ char m = plainText.charAt(i); BigInteger bi1 = BigInteger.valueOf(m); BigInteger bi2 = bi1.modPow(e, n); j = bi2.intValue(); m = (char) j; encrypted += m; } cipherText = encrypted; return encrypted; } public String decrypt() { String decrypted = ""; int j = 0; for(int i = 0; i < cipherText.length(); i++){ char c = cipherText.charAt(i); BigInteger bi1 = BigInteger.valueOf(c); BigInteger bi2 = bi1.modPow(d, n); j = bi2.intValue(); c = (char) j; decrypted += c; } return decrypted; } }

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  • C++: Comparing list of doubles with some invalid values (QNAN)

    - by J.M.
    Hello, i need to compare two std::list < double , but some doubles may be invalid numbers (QNAN). If any invalid numbers are list entries the compare process won't work, because a comparison of the same invalid value will always result in 'false'. What is the easiest and most elegant way to solve the problem? My idea was to create copies of both lists, iterate through them and remove invalid values and then compare the remaining lists. The lists will typically have 20-50 values in them. Is there a more resource friendly way to solve it?

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  • Impersonating a user in wrong domain doesn't throw exception

    - by Rita
    I've used the common impersonation code and it worked just fine, until I inserted random 'dggdgsdg' in domain - and it worked nonetheless... if (LogonUser(Username, Domain, Password, Logon32LogonInteractive, Logon32ProviderDefault, ref existingTokenHandle) && DuplicateToken(existingTokenHandle, (int)SecurityImpersonationLevel.SecurityDelegation, ref duplicateTokenHandle)) { Identity = new WindowsIdentity(duplicateTokenHandle); ImpersonationContext = Identity.Impersonate(); } else { throw new Win32Exception(Marshal.GetLastWin32Error()); } I used some TestUser on my domain, and it worked. I then switched domain, to random nonsense 'werwerhrg', and it impersonated the TestUser on my domain! Why? I would expect an exception to be thrown, why on earth is it working?

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  • How to execute a large PHP Script ?

    - by atif089
    Well basically I may want to execute a script that may take as much as 1 hours as well. What I really want to do is Send SMS to my users using a third party API. So its basically like I supply my script with an array of phone numbers and fire the method to send SMS. However assuming it take 5 seconds to send 1 SMS and I want to send 1000 SMS which is roughly 1 - 2 hours. I can use set_time_limit() because I am on shared host. One way to do this is store numbers in a session and execute each SMS and use javascript to refresh that page until end. This way I need to keep my browser open and the execution will stop if my Internet Connection is disconnected. So, Is there any better way to do this ? Hope I am clear enough to explain what I want? I want to execute a large script that may take hours to execute without getting timeout.

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  • zChaff not showing output

    - by pns
    Hello, So I downloaded the latest version of zChaff (2007), and was trying out some very simple SAT problems. But zChaff does not output the solution (variable assignments). A very simple example input: p cnf 2 2 1 2 0 1 -2 0 And what I get: c 2 Clauses are true, Verify Solution successful. Instance Satisfiable 1 -2 Random Seed Used 0 Max Decision Level 1 Num. of Decisions 2 ( Stack + Vsids + Shrinking Decisions ) 0 + 1 + 0 Original Num Variables 2 Original Num Clauses 2 Original Num Literals 4 Added Conflict Clauses 0 Num of Shrinkings 0 Deleted Conflict Clauses 0 Deleted Clauses 0 Added Conflict Literals 0 Deleted (Total) Literals 0 Number of Implication 2 Total Run Time 5.1e-05 RESULT: SAT I can see the 1 -2 on the left of "Random Seed Used", but shouldn't this be outputing the variable assignments as "v ..." ? Thanks

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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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  • Why does C++ mandate that complex only be instantiated for float, double, or long double?

    - by templatetypedef
    According to the C++ ISO spec, §26.2/2: The effect of instantiating the template complex for any type other than float, double or long double is unspecified. Why would the standard authors explicitly add this restriction? This makes it unspecified, for example, what happens if you make complex<int> or a complex<MyCustomFixedPointType> and seems like an artificial restriction. Is there a reason for this limitation? Is there a workaround if you want to instantiate complex with your own custom type? I'm primarily asking this question because of this earlier question, in which the OP was confused as to why abs was giving bizarre outputs for complex<int>. That said, this still doesn't quite make sense given that we also might want to make complex numbers out of fixed-points types, higher-precision real numbers, etc. Thanks!

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  • plane bombing problems- help

    - by peiska
    I'm training code problems, and on this one I am having problems to solve it, can you give me some tips how to solve it please. The problem is something like this: Your task is to find the sequence of points on the map that the bomber is expected to travel such that it hits all vital links. A link from A to B is vital when its absence isolates completely A from B. In other words, the only way to go from A to B (or vice versa) is via that link. Notice that if we destroy for example link (d,e), it becomes impossible to go from d to e,m,l or n in any way. A vital link can be hit at any point that lies in its segment (e.g. a hit close to d is as valid as a hit close to e). Of course, only one hit is enough to neutralize a vital link. Moreover, each bomb affects an exact circle of radius R, i.e., every segment that intersects that circle is considered hit. Due to enemy counter-attack, the plane may have to retreat at any moment, so the plane should follow, at each moment, to the closest vital link possible, even if in the end the total distance grows larger. Given all coordinates (the initial position of the plane and the nodes in the map) and the range R, you have to determine the sequence of positions in which the plane has to drop bombs. This sequence should start (takeoff) and finish (landing) at the initial position. Except for the start and finish, all the other positions have to fall exactly in a segment of the map (i.e. it should correspond to a point in a non-hit vital link segment). The coordinate system used will be UTM (Universal Transverse Mercator) northing and easting, which basically corresponds to a Euclidian perspective of the world (X=Easting; Y=Northing). Input Each input file will start with three floating point numbers indicating the X0 and Y0 coordinates of the airport and the range R. The second line contains an integer, N, indicating the number of nodes in the road network graph. Then, the next N (<10000) lines will each contain a pair of floating point numbers indicating the Xi and Yi coordinates (1 No two links will ever cross with each other. Output The program will print the sequence of coordinates (pairs of floating point numbers with exactly one decimal place), each one at a line, in the order that the plane should visit (starting and ending in the airport). Sample input 1 102.3 553.9 0.2 14 342.2 832.5 596.2 638.5 479.7 991.3 720.4 874.8 744.3 1284.1 1294.6 924.2 1467.5 659.6 1802.6 659.6 1686.2 860.7 1548.6 1111.2 1834.4 1054.8 564.4 1442.8 850.1 1460.5 1294.6 1485.1 17 1 2 1 3 2 4 3 4 4 5 4 6 6 7 7 8 8 9 8 10 9 10 10 11 6 11 5 12 5 13 12 13 13 14 Sample output 1 102.3 553.9 720.4 874.8 850.1 1460.5 102.3 553.9

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  • Popular open source projects using Zend Framework

    - by Alexander
    Hello, I am trying to find any open source project based on Zend Framework. Something well written and as popular as Wordpress or Drupal to see actual benefits of ZF as well as possibly use it as an example. The only 'showcase' I managed to find is http://framework.zend.com/wiki/pages/viewpage.action?pageId=14134. But this list looks confusing as for the 'official' PHP framework. The same is about ZF statistics by numbers (http://framework.zend.com/about/numbers) - 10 million downloads against 400 actual projects which is less than 500 examples in the user guide... Also Yahoo chose Symfony for their bookmarks service not ZF... Am I missing something? Thank you!

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  • [0-9a-zA-Z]* string expressed with primes or prime-factorization-style way to break it into parts?

    - by HH
    Suppose a string consists of numbers and alphabets. You want to break it into parts, an analogy is primes' factorization, but how can you do similar thing with strings [0-9a-zA-Z]* or even with arbitrary strings? I could express it in alphabets and such things with octal values and then prime-factorize it but then I need to keep track of places where I had the non-numbers things. Is there some simple way to do it? I am looking for simple succinct solutions and don't want too much side-effects. [Update] mvds has the correct idea, to change the base, how would you implement it?

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  • Please quickly help with this problem I got 52 minutes left.

    - by Hamish Grubijan
    Write a program that prints the numbers from 1 to 100. But for multiples of three print "Fizz" instead of the number and for the multiples of five print "Buzz". For numbers which are multiples of both three and five print "FizzBuzz". Woman said use any common language. Please make it short and test it. My screen is small. Thanks. P.S. I have test anxiety particularly after talking to people in suits. I also stayed up all night studying Java codes.

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  • Is it OK to mixed NumberLong and normal integers in the same field in MongoDB?

    - by Nicholas Tolley Cottrell
    I have been using Morphia to persistent objects from Java. I have also been running some batch processes from the console. I just realised that some values are now stored as NumberLong and number as plain Javascript numbers. I have an index on this field. Everything seems to be ok, but if I query: {f: 100} from the console it still returns the object even if it actually contains {f: NumberLong(100)} Is this true of all the drivers? It is best practice to avoid NumberLong is I can fit the value inside 32-bit? Will I save a lot of data and index space if I convert all NumberLongs to basic numbers?

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