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  • How to pass a member function to a function used in another member function?

    - by Tommaso Ferrari
    I found something about my problem, but I don't already understand very well. I need to do something like this: class T{ double a; public: double b; void setT(double par){ a=par; }; double funct(double par1) { return par1/a; } void exec(){ b=extfunct(funct, 10); } } double extfunct(double (*f)(double),double par2){ return f(par2)+5; } Operation and function are only for example, but the structure is that. The reason of this structure is that I have a precostituited class which finds the minimum of a gived function (it's extfunct in the example). So I have to use it on a function member of a class. I understood the difference between pointer to function and pointer to member function, but I don't understand how to write it. Thanks, and sorry for the poor explanation of the problem.

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  • Hash#key for 1.8.6

    - by Tobias
    Greetings, I am trying to make my 1.9.1 source 1.8.6 compatible. I recognized that there's no Hash#key method. Any idea or method how to solve that? Thanks! Tobias

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  • SQL Server 2000, yes 2000 password hash

    - by Justin808
    I need to store a password has in a SQL server 2000 database. The information isn't critical but I really don't want to store the password in clear text. How can I get a unique hash (sha, sha1, md5, etc) in SQL server 2000 as HashBytes isn't available. I'm not looking for compiled DLL or the ilk, I dont have access to the server, needs to be pure MS SQL.

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  • setting ruby hash .default to a list

    - by matpalm
    i thought i understood what the default method does to a hash... give a default value for a key if it doesn't exist irb(main):001:0> a = {} => {} irb(main):002:0> a.default = 4 => 4 irb(main):003:0> a[8] => 4 irb(main):004:0> a[9] += 1 => 5 irb(main):005:0> a => {9=>5} all good. but if i set the default to be a empty list, or empty hash, i dont understand it's behaviour at all.... irb(main):001:0> a = {} => {} irb(main):002:0> a.default = [] => [] irb(main):003:0> a[8] << 9 => [9] # great! irb(main):004:0> a => {} # ?! would have expected {8=>[9]} irb(main):005:0> a[8] => [8] # awesome! irb(main):006:0> a[9] => [9] # unawesome! shouldn't this be [] ?? i was hoping / expecting the same behaviour as if i had used the ||= operator... irb(main):001:0> a = {} => {} irb(main):002:0> a[8] ||= [] => [] irb(main):003:0> a[8] << 9 => [9] irb(main):004:0> a => {8=>[9]} irb(main):005:0> a[9] => nil can anyone explain what is going on ???

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  • computing hash values, integral types versus struct/class

    - by aaa
    hello I would like to know if there is a difference in speed between computing hash value (for example std::map key) of primitive integral type, such as int64_t and pod type, for example struct { int16_t v[4]; };. I know this is going to implementation specific, so my question ultimately pertains to gnu standard library. Thanks

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  • Good Hash Function for Strings

    - by Leif Andersen
    I'm trying to think up a good hash function for strings. And I was thinking it might be a good idea to sum up the unicode values for the first five characters in the string (assuming it has five, otherwise stop where it ends). Would that be a good idea, or is it a bad one? I am doing this in Java, but I wouldn't imagine that would make much of a difference.

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  • Use hash or case-statement [Ruby]

    - by user94154
    Generally which is better to use?: case n when 'foo' result = 'bar' when 'peanut butter' result = 'jelly' when 'stack' result = 'overflow' return result or map = {'foo' => 'bar', 'peanut butter' => 'jelly', 'stack' => 'overflow'} return map[n] More specifically, when should I use case-statements and when should I simply use a hash?

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  • hash password in mssql (asp.net)

    - by ile
    Is this how hashed password stored in mssql should look like? This is function I use to hash password (I found it in some tutorial) public string EncryptPassword(string password) { //we use codepage 1252 because that is what sql server uses byte[] pwdBytes = Encoding.GetEncoding(1252).GetBytes(password); byte[] hashBytes = System.Security.Cryptography.MD5.Create().ComputeHash(pwdBytes); return Encoding.GetEncoding(1252).GetString(hashBytes); } Thanks, Ile

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  • Perl, convert hash to array

    - by Mike
    If I have a hash in Perl that contains complete and sequential integer mappings (ie, all keys from from 0 to n are mapped to something), is there a means of converting this to an Array? I know I could iterate over the key/value pairs and place them into a new array, but something tells me there should be a built-in means of doing this.

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  • djb2 Hash Function

    - by Jainish
    I am using the djb2 algorithm to generate the hash key for a string which is as follows hash(unsigned char *str) { unsigned long hash = 5381; int c; while (c = *str++) hash = ((hash << 5) + hash) + c; /* hash * 33 + c */ return hash; } Now with every loop there is a multiplication with two big numbers, After some time with the 4th of 5th character of the string there is a overflow as the hash value becomes huge What is the correct way to refactor so that the hash value does not overflow and the hashing also happens correctly

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  • How to use the md5 hash?

    - by Ken
    Okay, so I'm learning php, html, and mysql to learn website development (for fun). One thing I still don't get is how to use md5 of sha1 hashes. I know how to hash the plain text, but say I want to make a login page. Since the password is hashed and can't be reversed, how would mysql know that the user-inserted password matches the hashed password in the database? Here is what I mean: $password = md5($_POST['password']); $query = ("INSERT INTO `users`.`data` (`password`) VALUES ('$password')"); I know that this snippet of script hashes the password, but how would I use this piece of code and make a login page? Any working examples would be great.

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  • Salt and hash a password in .NET

    - by Jon Canning
    I endeavoured to follow the CrackStation rules: Salted Password Hashing - Doing it Right    public class SaltedHash     {         public string Hash { get; private set; }         public string Salt { get; private set; }         public SaltedHash(string password)         {             var saltBytes = new byte[32];             new RNGCryptoServiceProvider().GetNonZeroBytes(saltBytes);             Salt = ConvertToBase64String(saltBytes);             var passwordAndSaltBytes = Concat(password, saltBytes);             Hash = ComputeHash(passwordAndSaltBytes);         }         static string ConvertToBase64String(byte[] bytes)         {             return Convert.ToBase64String(bytes);         }         static string ComputeHash(byte[] bytes)         {             return ConvertToBase64String(SHA256.Create().ComputeHash(bytes));         }         static byte[] Concat(string password, byte[] saltBytes)         {             var passwordBytes = Encoding.UTF8.GetBytes(password);             return passwordBytes.Concat(saltBytes).ToArray();         }         public static bool Verify(string salt, string hash, string password)         {             var saltBytes = Convert.FromBase64String(salt);             var passwordAndSaltBytes = Concat(password, saltBytes);             var hashAttempt = ComputeHash(passwordAndSaltBytes);             return hash == hashAttempt;         }     }

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  • Is perl's each function worth using?

    - by eugene y
    From perldoc -f each we read: There is a single iterator for each hash, shared by all each, keys, and values function calls in the program; it can be reset by reading all the elements from the hash, or by evaluating keys HASH or values HASH. The iterator is not reset when you leave the scope containing the each(), and this can lead to bugs: my %h = map { $_, 1 } qw(1 2 3); while (my $k = each %h) { print "1: $k\n"; last } while (my $k = each %h) { print "2: $k\n" } Output: 1: 1 2: 3 2: 2 What are the common workarounds for this behavior? And is it worth using each in general?

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  • Is perl's each function worth using?

    - by eugene y
    From perldoc -f each we read: There is a single iterator for each hash, shared by all each, keys, and values function calls in the program; it can be reset by reading all the elements from the hash, or by evaluating keys HASH or values HASH. The iterator is not reset when you leave the scope containing the each(), and this can lead to bugs: my %h = map { $_, 1 } qw(1 2 3); while (my $k = each %h) { print "1: $k\n"; last } while (my $k = each %h) { print "2: $k\n" } Output: 1: 1 2: 3 2: 2 What are the common workarounds for this behavior? And is it worth using each in general?

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  • Hash 32bit int to 16bit int?

    - by dkamins
    What are some simple ways to hash a 32-bit integer (e.g. IP address, e.g. Unix time_t, etc.) down to a 16-bit integer? E.g. hash_32b_to_16b(0x12345678) might return 0xABCD. Let's start with this as a horrible but functional example solution: function hash_32b_to_16b(val32b) { return val32b % 0xffff; } Question is specifically about JavaScript, but feel free to add any language-neutral solutions, preferably without using library functions. Simple = good. Wacky+obfuscated = amusing.

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  • Ruby: change each value in a hash with something like #collect for arrays?

    - by Adam Nonymous
    Hi! I'd like to replace each value in a hash with value.some_method. For example in a simple hash {"a" = "b", "c" = "d"} every value should be .upcase-d so it looks like {"a" = "B", "c" = "D"}. I tried #collect and #map but always just get arrays back. Is there an 'elegant' way to do this? Thanks in advance, Adam Nonymous UPDATE: Damn, I forgot: The hash is in an instance variable which should not be changed. I need a new hash with the changed values, but would prefer not to define that variable explicitly and then loop over the hash filling it. Something like new_hash = hash.magic {...} ;)

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  • Perfect hash in Scala.

    - by Lukasz Lew
    I have some class C: class C (...) { ... } I want to use it to index an efficient map. The most efficient map is an Array. So I add a "global" "static" counter in companion object to give each object unique id: object C { var id_counter = 0 } In primary constructor of C, with each creation of C I want to remember global counter value and increase it. Question 1: How to do it? Now I can use id in C objects as perfect hash to index array. But array does not preserve type information like map would, that a given array is indexed by C's id. Question 2: Is it possible to have it with type safety?

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  • Mapping multiple keys to the same value in a Javascript hash

    - by Bears will eat you
    I use a Javascript hash object to store a set of numerical counters, set up like this [this is greatly simplified]: var myHash = { A: 0, B: 0, C: 0 }; Is there a way to make other keys, ones not explicitly in myHash, map to keys that are? For instance, I'd like [again, this is simplified]: myHash['A_prime']++; // or myHash.A_prime++; to be exactly equivalent to myHash['A']++; // or myHash.A++; e.g. incrementing the value found at the key A, not A_prime.

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  • Summarize object area with a Hash in Ruby

    - by Arto Uusikangas
    require 'sketchup' entities = Sketchup.active_model.entities summa = Hash.new for face in entities next unless face.kind_of? Sketchup::Face if (face.material) summa[face.material.display_name] += face.area end end Im trying to get the structure in the array as such: summa { "Bricks" = 500, "Planks" = 4000 } Making a ruby script for Google Sketchup btw But if I run this code i only get Error: #+' for nil:NilClass> C:\Program Files (x86)\Google\Google SketchUp 7\Plugins\test.rb:17 C:\Program Files (x86)\Google\Google SketchUp 7\Plugins\test.rb:14:ineach' C:\Program Files (x86)\Google\Google SketchUp 7\Plugins\test.rb:14 C:\Program Files (x86)\Google\Google SketchUp 7\Plugins\test.rb:8:in `call' As im used to using PHP and just doing $array['myownassoc'] += bignumber; But i guess this isnt the right approach when using Ruby? So any help in how i need to go would be nice.

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  • hash password in SQL Server (asp.net)

    - by ile
    Is this how hashed password stored in SQL Server should look like? This is function I use to hash password (I found it in some tutorial) public string EncryptPassword(string password) { //we use codepage 1252 because that is what sql server uses byte[] pwdBytes = Encoding.GetEncoding(1252).GetBytes(password); byte[] hashBytes = System.Security.Cryptography.MD5.Create().ComputeHash(pwdBytes); return Encoding.GetEncoding(1252).GetString(hashBytes); } EDIT I tried to use sha-1 and now strings seem to look like as they are suppose to: public string EncryptPassword(string password) { return FormsAuthentication.HashPasswordForStoringInConfigFile(password, "sha1"); } // example output: 39A43BDB7827112409EFED3473F804E9E01DB4A8 Result from the image above looks like broken string, but this sha-1 looks normal.... Will this be secure enough?

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  • Merge a hash with the key/values of a string in ruby

    - by LazyJason
    Hi there, I'm trying to merge a hash with the key/values of string in ruby. i.e. h = {:day => 4, :month => 8, :year => 2010} s = "/my/crazy/url/:day/:month/:year" puts s.interpolate(h) All I've found is to iterate the keys and replace the values. But I'm not sure if there's a better way doing this? :) class String  def interpolate(e)    self if e.each{|k, v| self.gsub!(":#{k}", "#{v}")}  end end Thanks

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