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  • A more elegant way to parse a string with ruby regular expression using variable grouping?

    - by i0n
    At the moment I have a regular expression that looks like this: ^(cat|dog|bird){1}(cat|dog|bird)?(cat|dog|bird)?$ It matches at least 1, and at most 3 instances of a long list of words and makes the matching words for each group available via the corresponding variable. Is there a way to revise this so that I can return the result for each word in the string without specifying the number of groups beforehand? ^(cat|dog|bird)+$ works but only returns the last match separately , because there is only one group.

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  • Generating Fibonacci Numbers Using variable-Length Arrays Code Compiler Error.

    - by Nano HE
    Compile error in vs2010(Win32 Console Application Template) for the code below. How can I fix it. unsigned long long int Fibonacci[numFibs]; // error occurred here error C2057: expected constant expression error C2466: cannot allocate an array of constant size 0 error C2133: 'Fibonacci' : unknown size Complete code attached(It's a sample code from programming In c -3E book. No any modify) int main() { int i, numFibs; printf("How may Fibonacci numbers do you want (between 1 to 75)? "); scanf("%i", &numFibs); if ( numFibs < 1 || numFibs > 75){ printf("Bad number, sorry!\n"); return 1; } unsigned long long int Fibonacci[numFibs]; Fibonacci[0] = 0; // by definition Fibonacci[1] = 1; // ditto for ( i = 2; i < numFibs; ++i) Fibonacci[i] = Fibonacci[i-2] + Fibonacci[i-1]; for ( i = 0; i < numFibs; ++i) printf("%11u",Fibonacci[i]); printf("\n"); return 0; }

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  • Passing parameter to base class constructor or using instance variable?

    - by deamon
    All classes derived from a certain base class have to define an attribute called "path". In the sense of duck typing I could rely upon definition in the subclasses: class Base: pass # no "path" variable here def Sub(Base): def __init__(self): self.path = "something/" Another possiblity would be to use the base class constructor: class Base: def __init__(self, path): self.path = path def Sub(Base): def __init__(self): super().__init__("something/") What would you prefer and why? Is there a better way?

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  • Maximal Length of List to Shuffle with Python random.shuffle?

    - by Henrik
    I have a list which I shuffle with the Python built in shuffle function (random.shuffle) However, the Python reference states: Note that for even rather small len(x), the total number of permutations of x is larger than the period of most random number generators; this implies that most permutations of a long sequence can never be generated. Now, I wonder what this "rather small len(x)" means. 100, 1000, 10000,... Can anybody clarify? Thanks!

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  • hashing password giving different results

    - by geoff
    I am taking over a system that a previous developer wrote. The system has an administrator approve a user account and when they do that the system uses the following method to hash a password and save it to the database. It sends the unhashed password to the user. When the user logs in the system uses the exact same method to hash what the user enters and compares it to the database value. We've run into a couple of times when the database entry doesn't match the user's entry whey they should. So it appears that the method isn't always hashing the value the same. Does anyone know if this method of hashing isn't reliable and how to make it reliable? Thanks. private string HashPassword(string password) { string hashedPassword = string.Empty; // Convert plain text into a byte array. byte[] plainTextBytes = Encoding.UTF8.GetBytes(password); // Allocate array, which will hold plain text and salt. byte[] plainTextWithSaltBytes = new byte[plainTextBytes.Length + SALT.Length]; // Copy plain text bytes into resulting array. for(int i = 0; i < plainTextBytes.Length; i++) plainTextWithSaltBytes[i] = plainTextBytes[i]; // Append salt bytes to the resulting array. for(int i = 0; i < SALT.Length; i++) plainTextWithSaltBytes[plainTextBytes.Length + i] = SALT[i]; // Because we support multiple hashing algorithms, we must define // hash object as a common (abstract) base class. We will specify the // actual hashing algorithm class later during object creation. HashAlgorithm hash = new SHA256Managed(); // Compute hash value of our plain text with appended salt. byte[] hashBytes = hash.ComputeHash(plainTextWithSaltBytes); // Create array which will hold hash and original salt bytes. byte[] hashWithSaltBytes = new byte[hashBytes.Length + SALT.Length]; // Copy hash bytes into resulting array. for(int i = 0; i < hashBytes.Length; i++) hashWithSaltBytes[i] = hashBytes[i]; // Append salt bytes to the result. for(int i = 0; i < SALT.Length; i++) hashWithSaltBytes[hashBytes.Length + i] = SALT[i]; // Convert result into a base64-encoded string. hashedPassword = Convert.ToBase64String(hashWithSaltBytes); return hashedPassword; }

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  • C++ include statement required if defining a map in a headerfile.

    - by Justin
    I was doing a project for computer course on programming concepts. This project was to be completed in C++ using Object Oriented designs we learned throughout the course. Anyhow, I have two files symboltable.h and symboltable.cpp. I want to use a map as the data structure so I define it in the private section of the header file. I #include <map> in the cpp file before I #include "symboltable.h". I get several errors from the compiler (MS VS 2008 Pro) when I go to debug/run the program the first of which is: Error 1 error C2146: syntax error : missing ';' before identifier 'table' c:\users\jsmith\documents\visual studio 2008\projects\project2\project2\symboltable.h 22 Project2 To fix this I had to #include <map> in the header file, which to me seems strange. Here are the relevant code files: // symboltable.h #include <map> class SymbolTable { public: SymbolTable() {} void insert(string variable, double value); double lookUp(string variable); void init(); // Added as part of the spec given in the conference area. private: map<string, double> table; // Our container for variables and their values. }; and // symboltable.cpp #include <map> #include <string> #include <iostream> using namespace std; #include "symboltable.h" void SymbolTable::insert(string variable, double value) { table[variable] = value; // Creates a new map entry, if variable name already exist it overwrites last value. } double SymbolTable::lookUp(string variable) { if(table.find(variable) == table.end()) // Search for the variable, find() returns a position, if thats the end then we didnt find it. throw exception("Error: Uninitialized variable"); else return table[variable]; } void SymbolTable::init() { table.clear(); // Clears the map, removes all elements. }

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  • In C++, what happens when you return a variable?

    - by wowus
    What happens, step by step, when a variable is returned. I know that if it's a built-in and fits, it's thrown into rax/eax/ax. What happens when it doesn't fit, and/or isn't built-in? More importantly, is there a guaranteed copy constructor call? edit: What about the destructor? Is that called "sometimes", "always", or "never"?

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  • How to store the hostname in a variable in a .bat file?

    - by eqbridges
    I would like to convert this /bin/sh syntax into a widely compatible Windows batch script: host=`hostname` echo ${host} How to do this so that it'll work on any Windows Vista, Windows XP, and Windows 2000 machine? To clarify: I would then like to go on in the program and use the hostname as stored in the variable host. In other words, the larger goal of the program is not to simply echo the hostname.

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  • is it correct to unset the session variable for a particular index as the vay whole session is made

    - by OM The Eternity
    is it correct to unset the session variable for a particular index as the vay whole session is made unset in PHP? I know this works: unset($_SESSION['bannersize']) But does this works ? : unset($_SESSION['bannersize'][3]) or is there any other way to unset any particular desired index of the session and then again rearrange the values inside it to remove the empty index..?

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  • How to combine two arrays of same length to one array with two fields (not append/merge)

    - by Raj
    Say, I have an array with months $months = array('Jan', 'Feb', 'Mar'...'Dec'); And another, with days (say, for year 2010) $mdays = array(31, 28, 31...31); I want to merge/combine these two arrays, into an array like this: $monthdetails[0] = ('month' => 'Jan', 'days' => 31) $monthdetails[1] = ('month' => 'Feb', 'days' => 28) ... $monthdetails[11] = ('month' => 'Dec', 'days' => 31) I can loop through both the arrays and fill the $monthdetails. I want to know whether there are any functions/easier way for achieving the same result. Thanks! Raj

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  • Why does 'url' not work as a variable here?

    - by kryptobs2000
    I originally had the variable cpanel named url and the code would not return anything. Any idea why? It doesn't seem to be used by anything else, but there's gotta be something I'm overlooking. import urllib2 cpanel = 'http://www.tas-tech.com/cpanel' req = urllib2.Request(cpanel) try: handle = urllib2.urlopen(req) except IOError, e: if hasattr(e, 'code'): if e.code != 401: print 'We got another error' print e.code else: print e.headers print e.headers['www-authenticate']

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  • How can I save shell output to a variable in LaTeX?

    - by Frank
    I need to be able to execute a shell command through LaTeX [*] and have the resulting output available for use later on in the form of a LaTeX 'variable' (e.g., via a subsequent \newcommand command). If necessary a temporary file could be used to hold the output, although I would like to avoid this. I have been able to use \immediate\write18 to invoke a bash command before, but this was only used to write to a temporary file. [*] I realise that the -shell-escape flag must be set for this to be allowed

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