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• Is there a way to read 10000 lines from a file in python?

  - by windsound

  I am relatively new in python, was working on C a lot. Since I was seeing so many new functions in python that I do not know, I was wondering if there is a function that can request 10000 lines from a file in python. Something like this is what I expect if that kind of function exist: lines = get_10000_lines(file_pointer) Did python have a build-in function or is there any module that I can download for this? If not, how do I do this to be easiest way. I need to analyze a huge file so I want to read 10000 lines and analyze per time to save memory. Thanks for helping!

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• hierarchical data from self referencing table in tree form

  - by Beta033

  It looks like this has been asked and answered in all the simple cases, excluding the one that I'm having trouble with. I've tried using a recursive CTE to generate this; however maybe a cursor would be better? Or maybe a set of recursive functions will do the trick? Can this be done in a cte? consider the following table PrimaryKey ParentKey 1 NULL 2 1 3 6 4 7 5 2 6 1 7 NULL should yield PK 1 -2 --5 -6 --3 7 -4 where the number of - marks equal the depth, my primary difficulty is the ordering.

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• C++: Switching from MSVC to G++: Global Variables

  - by feed the fire

  I recently switched to Linux and wanted to compile my Visual Studio 2010 C++ source code, which uses only the STL, on G++. My Linux machine currently isn't available but I can try to tell you what is going on, first: As I try to compile my project, all global variables I use in main and which perfectly work on MSVC result in myGlobalVar is not defined in this scope errors. My project is built nearly the same as the example below: // myclass.h class myClass { // .... }; extern myClass globalInstance; // myclass.cpp #include "myclass.h" // myClass functions located here myClass globalInstance; // main.cpp #include "myclass.h" int main( ) { // Accessing globalInstance results in an error: Not defined in this scope } What am I doing wrong? Where are the differences between G++ and MSVC in terms of global variables?

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• How are clientside security vulnerabilities generally discovered?

  - by Jehjoa

  I mean in operating systems or their applications. The only way I can think of is examine binaries for the use of dangerous functions like strcpy(), and then try to exploit those. Though with compiler improvements like Visual Studio's /GS switch this possibility should mostly be a thing of the past. Or am I mistaken? What other ways do people use to find vulnerabilities? Just load your target in a debugger, then send unexpected input and see what happens? This seems like a long and tedious process. Could anyone recommend some good books or websites on this subject? Thanks in advance.

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• Lots of pointer casts in QGraphicsView framework and performance

  - by kleimola

  Since most of the convenience functions of QGraphicsScene and QGraphicsItem (such as items(), collidingItems(), childItems() etc.) return a QList you're forced to do lots of qgraphicsitem_cast or static_cast and QGraphicsItem::Type() checks to get hold of the actual items when you have lots of different type of items in the scene. I thought doing lots of subclass casts were not a desirable coding style, but I guess in this case there are no other viable way, or is there? QList<QGraphicsItem *> itemsHit = someItem->collidingItems(Qt::IntersectsItemShape); foreach (QGraphicsItem *item, itemsHit) { if (item->type() == QGraphicsEllipseItem::type()) { QGraphicsEllipseItem *ellipse = qgraphicsitem_cast<QGraphicsEllipseItem *>(item); // do something } else if (item->type() == MyItemSubclass::type()) { MyItemSubClass *myItem = qgraphicsitem_cast<MyItemSubClass *>(item); // do something } // etc } The above qgraphicsitem_cast could be replaced by static_cast since correct type is already verified. When doing lots of these all the time (very dynamic scene), will the numerous casting affect performance beyond the normal if-else evaluation?

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• Java combine parents of two large inheritance chains

  - by Soylent Green

  I have two parent classes in a huge project, let's say ClassA and ClassB. Each class has many subclasses, which in turn have many subclasses, which in turn have many subclasses, etc. My task is to "marry" these two "families" so that both inherit from a SINGLE parent. I need to essentially make ClassA and ClassB one class (parent) to both of their combined subclasses (children). ClassA and ClassB both currently implement Serializable. I am currently trying to make both inheritance chains inherit from ClassA, and then copy all functions and data members from ClassB into ClassA. This is tedious, and I think a terrible solution. What would be the CORRECT way to solve this problem?

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• Syncronizing indices of function pointer table to table contents

  - by Thomas Matthews

  In the embedded system I'm working on, we are using a table of function pointers to support proprietary Dynamic Libraries. We have a header file that uses named constants (#define) for the function pointer indices. These values are used in calculating the location in the table of the function's address. Example: *(export_table.c)* // Assume each function in the table has an associated declaration typedef void (*Function_Ptr)(void); Function_Ptr Export_Function_Table[] = { 0, Print, Read, Write, Process, }; Here is the header file: *export_table.h* #define ID_PRINT_FUNCTION 1 #define ID_READ_FUNCTION 2 #define ID_WRITE_FUNCTION 3 #define ID_PROCESS_FUNCTION 4 I'm looking for a scheme to define the named constants in terms of their location in the array so that when the order of the functions changes, the constants will also change. (Also, I would like the compiler or preprocessor to calculate the indices to avoid human mistakes like typeo's.)

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• Unexpected result from reduce function

  - by StackedCrooked

  I would like to get the smallest element from a vector. For this I use combine the reduce and min functions. However, when providing my own implementation of min I get unexpected results: user=> (reduce (fn [x y] (< x y) x y) [1 2 3 2 1 0 1 2]) 2 user=> (reduce min [1 2 3 2 1 0 1 2 3]) 0 The reduce with standard min returns 0 as expected. However, when I provide my own implementation it returns 2. What am I doing wrong?

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• When are C++ macros beneficial?

  - by Motti

  The C preprocessor is justifiably feared and shunned by the C++ community. In-lined functions, consts and templates are usually a safer and superior alternative to a #define. The following macro: #define SUCCEEDED(hr) ((HRESULT)(hr) >= 0) is in no way superior to the type safe: inline bool succeeded(int hr) { return hr >= 0; } But macros do have their place, please list the uses you find for macros that you can't do without the preprocessor. Please put each use-cases in a seperate answer so it can be voted up and if you know of how to achieve one of the answers without the preprosessor point out how in that answer's comments.

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• Return from parent sub in Perl

  - by JS Bangs

  I want to write a subroutine which causes the caller to return under certain conditions. This is meant to be used as a shortcut for validating input to a function. What I have so far is: sub needs($$) { my ($condition, $message) = @_; if (not $condition) { print "$message\n"; # would like to return from the *parent* here } return $condition; } sub run_find { my $arg = shift @_; needs $arg, "arg required" or return; needs exists $lang{$arg}, "No such language: $arg" or return; # etc. } The advantage of returning from the caller in needs would then be to avoid having to write the repetitive or return inside run_find and similar functions.

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• How to give 'Everybody' full rights to a file (programmatically)

  - by egrunin

  I'm modifying an old C++ program to run on Vista. It does not require Admin privileges. I've changed the code to put logfiles in \ProgramData\MyApp\. These logfiles are written with the stdio functions (fopen, fprintf, fclose). Here's the problem: UserA runs the program first, it creates \ProgramData\MyApp\MyLogFile.txt UserB runs the program next, it tries to append to MyLogFile.txt and gets access denied. I tried creating a null SECURITY_DESCRIPTOR and passing that to CreateFile(). That does create a file with "no permissions assigned", but it seems as if the first user to write to the file takes ownership and afterwards all the other non-admin users are out of luck. It's important that all users share the same logfiles, but it's also important that I change as little code as possible.

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• Implementing N-tire structure in .net

  - by pravakar

  Hi friends, my requirement is suppose i have three classes namely Employee, Customer and Department where Employee contains attributes i.e. id,name,dept and Customer class contains Id,name and Department class contains i.e. id and name. Now all these three class has common function i.e. create, update and delete. This functions i want to implement using interface. So can any one suugest me to perform these things in n-tier architecture.

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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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• How can I set breakpoints in an external JS script in Firebug

  - by Manu

  I can easily set breakpoints in embedded JS functions, but I don't see any way of accessing extarnal JS scripts via Firebug unless I happen to enter them during a debug session. Is there a way to do this w/o having to 'explore' my way into the script? @Jason: This is a good point, but in my case I do not have easy access to the script. I am specifically talking about the client scripts which are invoked by the ASP.Net Validators that I would like to debug. I can access them during a debug session through entering the function calls, but I could not find a way to access them directly.

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• using ajax url to call function

  - by Steven Vanerp

  Hopefully I can ask this correctly cuz I know what I want it to do but can't seem to find any answers from searching. I have a func.php page where I have all my functions and I want ajax to use one function from that page. func.php function toptable() { echo"something happens in here"; } index.php <?php include 'func.php'; ?> <script type="text/javascript"> function check_username() { uname=document.getElementById("username").value; var params = "user_id="+uname; var url = "topoftable()"; $.ajax({ type: 'POST', url: url, dataType: 'html', data: params, beforeSend: function() { document.getElementById("right").innerHTML= 'checking' ; }, complete: function() { }, success: function(html) { document.getElementById("right").innerHTML= html ; } }); } </script> Make sense?

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• MySql returning multiple rows from stored procedure / function

  - by pistacchio

  Hi, I need to make a stored procedure or function that returns a set of rows. I've noted that in a stored procedure i can SELECT * FROM table with success. If i fetch rows in a loop and SELECT something, something_other FROM table once per loop execution, I only get one single result. What I need to do is looping, doing some calculations and returning a rowset. What's the best way to do this? A temporary table? Stored functions? Any help appreciated.

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• So I dynamically load a jar at runtime how do I use it?

  - by justinhj

  So question 194698 shows how to load a jar file at runtime and you can load individual named classes and get a Class object. Now my problem is I want to be able to cast those Classes to the types they really are, but I can't because I can't use an import since the whole point is to load it at runtime rather than compile time. It seems like the way to go is to use reflection to discover the functions and field names, but that seems brittle since the API in the jar files could change and the code won't break until it is run. Is there a better way?

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• Indexing XMLType columns

  - by Chris

  Hello, I am working with a XMLType and currently experiencing significant performance issues and would like to incorporate indexing to the column type. Currently I am taking the approach of using the XMLTable() and XQuery functions to create a virtual table. I would like to use this Virtual Table to create a function based index on the table containing the XMLType, but I am receiving this error: Error report: SQL Error: ORA-00907: missing right parenthesis 00907. 00000 - "missing right parenthesis" *Cause: *Action: This is the index.. any assistance would be greatly appreciated. CREATE INDEX indx_medicinalproduct ON d.ProductName XMLTable('for $i at $a in /safetyreport/patient//drug for $j in $i/medicinalproduct return element r { $i/medicinalproduct }' PASSING s.safetyreport COLUMNS ProductName varchar2(70) PATH 'medicinalproduct') d;

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• Handling the distinction between undefined- and null-parameters in JavaScript

  - by Jakob

  I know very well that null and undefined are distinct in JavaScript. However, I can't seem to decide whether or not use that fact when my own functions are passed one of those as its argument. Or, expressed in a different way, should myFoo(undefined) return the same thing as myFoo(null) or is everything fine if it doesn't? Or, in yet another case, since myBar(1, 2, 3) is the same thing as myBar(1, 2, 3, undefined, undefined), should myBar(1, 2, 3, null, null) return the same thing as myBar(1, 2, 3)? I feel that there's potential for confusion in both cases and that a library should probably follow a convention when handling null/undefined. I'm not really asking for personal opinions (so please express those as comments rather than answers). I'm asking if anyone knows if there is a best practice that one should stick to when it comes to handling this distinction. References to external sources are very welcome!

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• How to use a Visual C++ .Net String type as argument in a function

  - by stefangachter

  Probably this is not a difficult question, but I am always a little bit confused on how to treat String type as an argument in Visual C++. I have the following to functions: void function_1(String ^str_1) { str_1 = gcnew String("Test"); } void function_2() { String ^str_2 = nullptr; function_1(str_2); } After calling function_1, str_2 is still equal to null, but what I want to achieve is that str_2 is equal to Test. So, how can I achieve that the content of str_1 is passed to function_2? Thanks for any advice.

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• Separate one-off code paths

  - by DeadMG

  I'm implementing an application with different code paths that shall be chosen once at startup and then fixed forevermore for that execution- for example, choosing D3D11 or D3D9 rendering path. Obviously I don't want to duplicate all my other code. Is run-time inheritance (no virtual inheritance) a fair solution? I don't want to waste a bunch of performance making virtual lookups when the type was fixed long ago. Not just that, but it makes me nervous that the functions can't be inlined and whether or not it affects RVO and NRVO and such. Am I just being over-concerned about this?

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• Radio Buttons not highlighting as though they are selected

  - by Ryan

  I'm working on an android activity with a RadioGroup containing 10 RadioButtons. For some reason or another sometimes, only sometimes, when you select a RadioButton in the RadioGroup it doesn't highlight as if it's selected but through some tests I've determined that it really IS selected even though it isn't highlighted. Another odd thing that occurs is that when you select any other RadioButton in the RadioGroup and then try selecting your original Radio Button (the one that wouldn't highlight as though it were selected) it does highlight and functions as normal. Any idea why this is happening or how to fix it? Thanks!

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• NSPredicate aggregate function [SIZE] gives 'unsupported function expression' error

  - by jinglesthula

  iOS 4: I have entities in Core Data (using SQLite, which is a requirement) of: Request Response (which has a property personId) Revision Relationships are: Request <-- Revision Request <-- Response Revision <-- Response (e.g. each request may have many responses; each request/response pair may have many revisions) I'm trying to do a predicate to get all Responses with a given personId that have zero Revisions. Using: (personId == %d) && (Request.Revision[SIZE] == 0) in my predicate string gives me a runtime exception "Unsupported function expression Request.Revision[SIZE]" The documentation seems pretty sparse on aggregate functions, only noting that they exist, but with no syntax or examples. Not sure if it's my syntax or if the SIZE function really isn't supported in iOS.

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• strtok program crashing.

  - by baskin

  Hi, the program for strtok given on http://www.opengroup.org/onlinepubs/000095399/functions/strtok.html crashes everytime.. #include <string.h> ... char *token; char *line = "LINE TO BE SEPARATED"; char *search = " "; /* Token will point to "LINE". */ token = strtok(line, search); /* Token will point to "TO". */ token = strtok(NULL, search); If I use a char array for variable 'line', it works. i.e. char line[] = "LINE TO BE SEPARATED" works. Kindly explain.

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• ORA-00937 error during select subquery

  - by RedRaven

  I am attempting to write a query that returns the the number of employees, the average salary, and the number of employees paid below the average. The query I have so far is: select trunc(avg(salary)) "Average Pay", count(salary) "Total Employees", ( select count(salary) from employees where salary < (select avg(salary) from employees) ) UnderPaid from employees; But when I run this I get the ora-00937 error in the subquery. I had thought that maybe the "count" function is what is causing the issue, but even running a simpler sub query such as: select trunc(avg(salary)) "Average Pay", count(salary) "Total Employees", ( select avg(salary) from employees ) UnderPaid from employees; still returns the same error. As both AVG and COUNT seem to be aggregate functions, I'm not sure why I'm getting the error? Thanks

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