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  • Is there a shorthand way to denullify a string in C#?

    - by Moose Factory
    Is there a shorthand way to denullify a string in C#? It would be the equivalent of (if 'x' is a string): string y = x == null ? "" : x; I guess I'm hoping there's some operator that would work something like: string y = #x; Wishful thinking, huh? The closest I've got so far is an extension method on the string class: public static string ToNotNull(this string value) { return value == null ? "" : value; } which allows me to do: string y = x.ToNotNull(); Any improvements on that, anyone?

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  • C++: conjunction of binds?

    - by Helltone
    Suppose the following two functions: #include <iostream> #include <cstdlib> // atoi #include <cstring> // strcmp #include <boost/bind.hpp> bool match1(const char* a, const char* b) { return (strcmp(a, b) == 0); } bool match2(int a, const char* b) { return (atoi(b) == a); } Each of these functions takes two arguments, but can be transformed into a callable object that takes only one argument by using (std/boost)bind. Something along the lines of: boost::bind(match1, "a test"); boost::bind(match2, 42); I want to be able to obtain, from two functions like these that take one argument and return bool, a callable object that takes two arguments and returns the && of the bools. The type of the arguments is arbitrary. Something like an operator&& for functions that return bool.

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  • sys.path() and PYTHONPATH issues

    - by Justin
    I've been learning Python, I'm working in 2.7.3, and I'm trying to understand import statements. The documentation says that when you attempt to import a module, the interpreter will first search for one of the built-in modules. What is meant by a built-in module? Then, the documentation says that the interpreter searches in the directories listed by sys.path, and that sys.path is initialized from these sources: the directory containing the input script (or the current directory). PYTHONPATH (a list of directory names, with the same syntax as the shell variable PATH). the installation-dependent default. Here is a sample output of a sys.path command from my computer using python in command-line mode: (I deleted a few so that it wouldn't be huge) ['', '/usr/lib/python2.7', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PIL', '/usr/lib/python2.7/dist-packages/gst-0.10', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/pymodules/python2.7', '/usr/lib/python2.7/dist-packages/ubuntuone-couch', '/usr/lib/python2.7/dist-packages/ubuntuone-storage-protocol'] Now, I'm assuming that the '' path refers to the directory containing the 'script', and so I figured the rest of them would be coming from my PYTHONPATH environmental variable. However, when I go to the terminal and type env, PYTHONPATH doesn't exist as an environmental variable. I also tried import os then os.environ, but I get the same output. Do I really not have a PYTHONPATH environmental variable? I don't believe I ever specifically defined a PYTHONPATH environmental variable, but I assumed that when I installed new packages they automatically altered that environment variable. If I don't have a PYTHONPATH, how is my sys.path getting populated? If I download new packages, how does Python know where to look for them if I don't have this PYTHONPATH variable? How do environment variables work? From what I understand, environment variables are specific to the process for which they are set, however, if I open multiple terminal windows and run env, they all display a number of identical variables, for example, PATH. I know there file locations for persistent environment variables, for example /etc/environment, which contains my PATH variable. Is it possible to tell where a persistent environment variable is stored? What is the recommended location for storing new persistent environment variables? How do environment variables actually work with say, the Python interpreter? The Python interpreter looks for PYTHONPATH, but how does it work at the nitty-gritty level?

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  • Undefined / Uninitialized default values in a class

    - by Jir
    Let's suppose you have this class: class A { public: A () {} A (double val) : m_val(val) {} ~A () {} private: double m_val; }; Once I create an instance of A, how can I check if m_val has been initialized/defined? Put it in other words, is there a way to know if m_val has been initialized/defined or not? Something along the lines of the defined operator in Python, I suppose. (But correct me if I'm wrong.) I thought of modifying the class and the c-tors the following way: class A { public: A () : defined(false) {} A (double val) : m_val(val), defined(true) {} ~A () {} private: double m_val; bool defined; }; How do you rate this solution? Any suggestion? TIA, Chris

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  • Storing expression template functors

    - by UncaughtException
    Hello guys, at the moment I'm really interested in expression templates and want to code a library for writing and differentiating mathematical functions with a lambda-style syntax. At the moment, I'm able to write (_x * _x)(2); and get the correct result 4. But I would really like to do something like MathFunction f = _x * _x; f(2);, but I don't have any ideas on how to cope with the recursive expression templates on the right side. Is it possible to achieve this without using the 'auto'-Keyword instead of MathFunction or having to make the operator() virtual? Thanks for your help!

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  • What does this `_time_independent_equals` mean?

    - by Satoru.Logic
    In the tornado.web module there is a function called _time_independent_equals: def _time_independent_equals(a, b): if len(a) != len(b): return False result = 0 for x, y in zip(a, b): result |= ord(x) ^ ord(y) return result == 0 It is used to compare secure cookie signatures, and thus the name. But regarding the implementation of this function, is it just a complex way to say a==b?

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  • how to create internal frame?

    - by joseph
    I created class NewProject extends JInternalFrame. Then I create New...Action named "NEW", localised in File menu. I put code NewProject p = new NewProject(); p.setVisible(true); to the ActionPerformed method of the action. But when I run the module and click "NEW" in file menu, nothing appears. Where can be problem?

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  • fastest method for minimum of two numbers

    - by user85030
    I was going through mit's opencourseware related to performance engineering. The quickest method (requiring least number of clock cycles) for finding the minimum of two numbers(say x and y) is stated as: min= y^((x^y) & -(x<y)) The output of the expression x < y can be 0 or 1 (assuming C is being used) which then changes to -0 or -1. I understand that xor can be used to swap two numbers. Questions: 1. How is -0 different from 0 and -1 in terms of binary? 2. How is that result used with the and operator to get the minimum? Thanks in advance.

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  • How do I run an interactive command line Python app inside of Emacs on Win32?

    - by sludge
    If I use M-x shell and run the interactive Python interpreter, Emacs on Windows does not return any IO. When I discovered M-x python-shell, I regained hope. However, instead of running the interactive Python shell, I want to run a specific Python script that features an interactive CLI. (See Python's cmd module for details). Is there a way of launching a Python script in Emacs that is interactive? (stdout, stdin, stderr)

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  • What is wrong with my SQL syntax for an UPDATE with a JOIN?

    - by Phil H
    I have two tables, related by a common key. So TableA has key AID and value Name and TableB has keys AID, BID and values Name, Value: AID Name 74 Alpha AID BID Name Value 74 4 Beta Brilliance I would like to update the TableB Value here from Brilliance to Barmy, using just the Name fields. I thought I could do it via an UPDATE containing a JOIN, but Access (I know...) is complaining with 'Syntax error (missing operator) in query expression ' and then everything from 'Barmy' here: UPDATE tB SET tB.BValue='Barmy' FROM TableB tB INNER JOIN TableA tA ON tB.AID=tA.AID WHERE tB.Name='Beta' AND tA.Name='Alpha'; What is my heinous crime? Or is it just Access not conforming?

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  • GPRS remote printer

    - by user160108
    We have a custom remote printer designed with GPRS module. We now need to communicate with the device over the web. We have to send messages and receive messages from the remote printer, can i do this using Java or PHP. How do i communicate through GPRS? Will socket communication work?

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  • Any way in C++ to forward declare a function prototype?

    - by jsyjr
    I make regular use of forward class declarations and pointers to such classes. I now have a need to pass a function pointer through a number of layers. I would prefer to include the header that declares my function pointer's prototype only into the module that dereferences a function pointer rather than into each layer that simply passes along that pointer value. Is this possible?

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  • Using pipes inside a class in C++

    - by Paul
    I'm trying to use this tutorial to make plots with Gnuplot in C++. However I will be using the pipe to Gnuplot from within a class, but then I run into some problems: I've got a header file where I declare all variables etc. I need to declare the pipe-variable here too, but how do I do that? I've tried doing it straight away, but it doesn't work: Logger.h: class Logger { FILE pipe; } Logger.cpp: Logger::Logger() { //Constructor *pipe = popen("gnuplot -persist","w"); } Gives the error Logger.cpp:28: error: no match for ‘operator=’ in ‘*((Logger*)this)->Logger::pipe = popen(((const char*)"gnuplot -persist"), ((const char*)"w"))’ Suggestions?

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  • Purpose of IF, ELSE, FOR macros ?

    - by psihodelia
    I have a source code of a library which has a lot of strange IF, ELSE, FOR, etc. macros for all common C-keywords instead of using just usual if,else,for,while keywords. These macros are defined like this: #define IF( a) if( increment_if(), a) where increment_if() function is defined so: static __inline void increment_if( void) { // If the "IF" operator comes just after an "ELSE", its counter // must not be incremented. ... //implementation } I don't really understand, what is the purpose of such macros? This library is for a real-time application and I suppose that using such macros must slow-down an application.

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  • What does this `_time_independent_equlas` mean?

    - by Satoru.Logic
    In the tornado.web module there is a function called _time_independent_equals: def _time_independent_equals(a, b): if len(a) != len(b): return False result = 0 for x, y in zip(a, b): result |= ord(x) ^ ord(y) return result == 0 It is used to compare secure cookie signatures, and thus the name. But regarding the implementation of this function, is it just a complex way to say a==b?

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  • how to identify process in kernel read func without using current->pid

    - by yoavstr
    my lecture wants us to build module where we need to identify each read process and where the same read process called twice on the same writer massage we should insert him to an queue who's we wake up when all readers have read I achieved this goal by by using list of pid's and boolean read/not_read inside each node but he decided to be nasty and require us to it with some argument from FILE struct can you please help me ?....

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  • how to call a javascript fucntion from an included javacript file using GWT?

    - by subh
    I have a function Load() in a js file which I added to the GWT module. I am trying to call it using private static native void load() /*-{ $doc.Load(); }-*/; but it gives me error like Error(s) occurred! (TypeError): $doc.Load is not a function fileName: http://localhost:8888/myapp/888C05FB242806B071A932498F6B5AD9.cache.html lineNumber: 1224 I even tried with $wnd.Load() What the proper way of calling it?

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  • ActionScript: Using 'in' on protected/private variables?

    - by David Wolever
    Is there any way to mimic the in operator, but testing for the existence of protected or private fields? For example, this: <mx:Script><![CDATA[ public var pub:Boolean = true; protected var prot:Boolean = true; private var priv:Boolean = true; ]]></mx:Script> <mx:creationComplete><![CDATA[ for each (var prop in ["pub", "prot", "priv", "bad"]) trace(prop + ":", prop in this); ]]></mx:creationComplete> Will trace: pub: true prot: false priv: false bad: false When I want to see: pub: true prot: true priv: true bad: false

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  • Best way to package a class for use in another app?

    - by Brad Hein
    I've written an Android app wich various abstract classes that perform useful functions. These functions could be leveraged in other apps. I want to share a class module with another programmer, but I don't want to share the source code. I would like to share a .class file but I'm not sure how to do the following: Compile an Android .java file into .class What does the receiver of the .class file have to do to use that .class in their project? (using Eclipse environment) Thank you very much

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  • C underscore prototype syntax

    - by lobsterriffic
    I was trying to compile a ruby module, and my compiler choked. I think it might have something to do with a line in ruby.h: void rb_check_type _((VALUE,int)); I've never seen this _ syntax before. What does it mean? Could it cause problems for my compiler (Visual Studio)?

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  • exeuting command in background

    - by tazim
    Hi, Trying to execute shell command in background using pythons commands module >>>import commands >>>output = commands.getstatusoutput("find / > tmp.txt &") sh: Syntax error: ";" unexpected Can anyone explain what is wrong with the syntax ? How should it be executed then ? Tazim.

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