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• setcontext and makecontext to call a generic function pointer

  - by Simone Margaritelli

  In another question i had the problem to port the code unsigned long stack[] = { 1, 23, 33, 43 }; /* save all the registers and the stack pointer */ unsigned long esp; asm __volatile__ ( "pusha" ); asm __volatile__ ( "mov %%esp, %0" :"=m" (esp)); for( i = 0; i < sizeof(stack); i++ ){ unsigned long val = stack[i]; asm __volatile__ ( "push %0" :: "m"(val) ); } unsigned long ret = function_pointer(); /* restore registers and stack pointer */ asm __volatile__ ( "mov %0, %%esp" :: "m" (esp) ); asm __volatile__ ( "popa" ); To a 64bit platform and many guys told me i should use the setcontext and makecontext functions set instead due to the calling conversion differences between 32 and 64 bits and portability issues. Well, i really can't find any useful documentation online, or at least not the kind i need to implement this, so, how can i use those functions to push arguments onto the stack, call a generic function pointer, obtain the return value and then restore the registers?

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• Using Pragma in Oracle Package Body

  - by asalamon74

  I'd like to create an Oracle Package and two functions in it: A public function ( function_public ) and a private one ( function_private ). The public function calls the private one. I'd like to add the same pragma to the functions: WNDS, WNPS. Without the pragma I can create a code like this: CREATE OR REPLACE PACKAGE PRAGMA_TEST AS FUNCTION function_public(x IN VARCHAR2) RETURN VARCHAR2; END PRAGMA_TEST; CREATE OR REPLACE PACKAGE BODY PRAGMA_TEST AS FUNCTION function_private(y IN VARCHAR2) RETURN VARCHAR2 IS BEGIN -- code END; FUNCTION function_public(x IN VARCHAR2) RETURN VARCHAR2 IS BEGIN -- code -- here is a call for function_private -- code END; END PRAGMA_TEST; If I'd like to add WNDS, WNPS pragma to function_public I should also add the same pragma to function_private because function_public calls function_private. It seems to me pragma can be used only in the package declaration, and not in package body, so I have to declare function_private in the package as well: CREATE OR REPLACE PACKAGE PRAGMA_TEST AS FUNCTION function_private(y IN VARCHAR2) RETURN VARCHAR2; PRAGMA RESTRICT_REFERENCES( function_private, WNDS, WNPS); FUNCTION function_public(x IN VARCHAR2) RETURN VARCHAR2; PRAGMA RESTRICT_REFERENCES( function_public, WNDS, WNPS); END PRAGMA_TEST; CREATE OR REPLACE PACKAGE BODY PRAGMA_TEST AS FUNCTION function_private(y IN VARCHAR2) RETURN VARCHAR2 IS BEGIN -- code END; FUNCTION function_public(x IN VARCHAR2) RETURN VARCHAR2 IS BEGIN -- code -- here is a call for function_private -- code END; END PRAGMA_TEST; This solution makes my function_private public as well. Is there a solution to add pragma to a function which can be found only in the package body?

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• Possible to Inspect Innards of Core C# Functionality

  - by Nick Babcock

  I was struck today, with the inclination to compare the innards of Buffer.BlockCopy and Array.CopyTo. I am curious to see if Array.CopyTo called Buffer.BlockCopy behind the scenes. There is no practical purpose behind this, I just want to further my understanding of the C# language and how it is implemented. Don't jump the gun and accuse me of micro-optimization, but you can accuse me of being curious! When I ran ILasm on mscorlib.dll I received this for Array.CopyTo .method public hidebysig newslot virtual final instance void CopyTo(class System.Array 'array', int32 index) cil managed { // Code size 0 (0x0) } // end of method Array::CopyTo and this for Buffer.BlockCopy .method public hidebysig static void BlockCopy(class System.Array src, int32 srcOffset, class System.Array dst, int32 dstOffset, int32 count) cil managed internalcall { .custom instance void System.Security.SecuritySafeCriticalAttribute::.ctor() = ( 01 00 00 00 ) } // end of method Buffer::BlockCopy Which, frankly, baffles me. I've never run ILasm on a dll/exe I didn't create. Does this mean that I won't be able to see how these functions are implemented? Searching around only revealed a stackoverflow question, which Marc Gravell said [Buffer.BlockCopy] is basically a wrapper over a raw mem-copy While insightful, it doesn't answer my question if Array.CopyTo calls Buffer.BlockCopy. I'm specifically interested in if I'm able to see how these two functions are implemented, and if I had future questions about the internals of C#, if it is possible for me to investigate it. Or am I out of luck?

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• When *not* to use prepared statements?

  - by Ben Blank

  I'm re-engineering a PHP-driven web site which uses a minimal database. The original version used "pseudo-prepared-statements" (PHP functions which did quoting and parameter replacement) to prevent injection attacks and to separate database logic from page logic. It seemed natural to replace these ad-hoc functions with an object which uses PDO and real prepared statements, but after doing my reading on them, I'm not so sure. PDO still seems like a great idea, but one of the primary selling points of prepared statements is being able to reuse them… which I never will. Here's my setup: The statements are all trivially simple. Most are in the form SELECT foo,bar FROM baz WHERE quux = ? ORDER BY bar LIMIT 1. The most complex statement in the lot is simply three such selects joined together with UNION ALLs. Each page hit executes at most one statement and executes it only once. I'm in a hosted environment and therefore leery of slamming their servers by doing any "stress tests" personally. Given that using prepared statements will, at minimum, double the number of database round-trips I'm making, am I better off avoiding them? Can I use PDO::MYSQL_ATTR_DIRECT_QUERY to avoid the overhead of multiple database trips while retaining the benefit of parametrization and injection defense? Or do the binary calls used by the prepared statement API perform well enough compared to executing non-prepared queries that I shouldn't worry about it? EDIT: Thanks for all the good advice, folks. This is one where I wish I could mark more than one answer as "accepted" — lots of different perspectives. Ultimately, though, I have to give rick his due… without his answer I would have blissfully gone off and done the completely Wrong Thing even after following everyone's advice. :-) Emulated prepared statements it is!

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• Data Access Layer, Best Practices

  - by labratmatt

  I'm looking for input on the best way to refactor the data access layer (DAL) in my PHP based web app. I follow an MVC pattern: PHP/HTML/CSS/etc. views on the front end, PHP controllers/services in the middle, and a PHP DAL sitting on top of a relational database in the model. Pretty standard stuff. Things are working fine, but my DAL is getting large (codesmell?) and becoming a bit unwieldy. My DAL contains almost all of the logic to interface with my database and is full of functions that look like this: function getUser($user_id) { $statement = "select id, name from users where user_id=:user_id"; PDO builds statement and fetchs results as an array return $array_of_results_generated_by_PDO_fetch_method; } Notes: The logic in my controller only interacts with the model using functions like the above in the DAL I am not using a framework (I'm of the opinion that PHP is a templating language and there's no need to inject complexity via a framework) I generally use PHP as a procedural language and tend to shy away from its OOP approach (I enjoy OOP development but prefer to keep that complexity out of PHP) What approaches have you taken when your DAL has reached this point? Do I have a fundamental design problem? Do I simply need to chop my DAL into a number of smaller files (logically divide it)? Thanks.

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• Getting Argument Names In Ruby Reflection

  - by Joe Soul-bringer

  I would like to do some fairly heavy-duty reflection in the Ruby programming language. I would like to create a function which would return the names of the arguments of various calling functions higher up the call stack (just one higher would be enough but why stop there?). I could use Kernel.caller go to the file and parse the argument list but that would be ugly and unreliable. The function that I would like would work in the following way: module A def method1( tuti, fruity) foo end def method2(bim, bam, boom) foo end def foo print caller_args[1].join(",") #the "1" mean one step up the call stack end end A.method1 #prints "tuti,fruity" A.method2 #prints "bim, bam, boom" I would not mind using ParseTree or some similar tool for this task but looking at Parsetree, it is not obvious how to use it for this purpose. Creating a C extension like this is another possibility but it would be nice if someone had already done it for me. Edit2: I can see that I'll probably need some kind of C extension. I suppose that means my question is what combination of C extension would work most easily. I don't think caller+ParseTree would be enough by themselves. As far as why I would like to do this goes, rather than saying "automatic debugging", perhaps I should say that I would like to use this functionality to do automatic checking of the calling and return conditions of functions. Say def add x, y check_positive return x + y end Where check_positive would throw an exception if x and y weren't positive (obviously, there would be more to it than that but hopefully this gives enough motivation)

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• How to use include within a function?

  - by mahks

  I have a large function that I wish to load only when it is needed. So I assume using include is the way to go. But I need several support functions as well -only used in go_do_it(). If they are in the included file I get a redeclare error. See example A If I place the support functions in an include_once it works fine, see Example B. If I use include_once for the func_1 code, the second call fails. -func_1 needs include -func_2 needs include_once Why does does include_once fail for func_1, does it get reloaded each time the function is called? Example A: <?php /* main.php */ go_do_it(); go_do_it(); function go_do_it(){ include 'func_1.php'; } ?> <?php /* func_1.php */ echo '<br>Doing it'; nested_func() function nested_func(){ echo ' in nest'; } ?> Example B: <?php /* main.php */ go_do_it(); go_do_it(); function go_do_it(){ include_once 'func_2.php'; include 'func_1.php'; } ?> <?php /* func_1.php */ echo '<br> - doing it'; nested_func(); ?> <?php /* func_2.php */ function nested_func(){ echo ' in nest'; } ?>

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• iPhone app rejection for using ICU (Unicode extensions)

  - by nickbit

  I received the following mail form Apple, considering my application: *Thank you for submitting your update to ??µ??es?a to the App Store. During our review of your application we found it is using private APIs, which is in violation of the iPhone Developer Program License Agreement section 3.3.1; "3.3.1 Applications may only use Documented APIs in the manner prescribed by Apple and must not use or call any private APIs." While your application has not been rejected, it would be appropriate to resolve this issue in your next update. The following non-public APIs are included in your application: u_isspace ubrk_close ubrk_current ubrk_first ubrk_next ubrk_open If you have defined methods in your source code with the same names as the above mentioned APIs, we suggest altering your method names so that they no longer collide with Apple's private APIs to avoid your application being flagged with future submissions. Please resolve this issue in your next update to ??µ??es?a. Sincerely, iPhone App Review Team* The functions mentioned in this mail are used in the ICU library (International Components for Unicode). Although my app is not rejected at this point, I don't feel very secure for the future of my app, because it relies heavily on the Unicode protocol and on this components in particular. Another thing is that I do not call these functions directly, but they are called by a custom 'sqlite' build (with FTS3 extensions enabled). Am I missing something here? Any suggestions?

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• In languages which create a new scope each time in a loop block, a new local copy of the local loop

  - by Jian Lin

  It seems that in language like C, Java, and Ruby (as opposed to Javascript), a new scope is created for each iteration of a loop block, and the local variable defined for the loop is actually made into a local variable every single time and recorded in this new scope? For example, in Ruby: p RUBY_VERSION $foo = [] (1..5).each do |i| $foo[i] = lambda { p i } end (1..5).each do |j| $foo[j].call() end the print out is: [MacBook01:~] $ ruby scope.rb "1.8.6" 1 2 3 4 5 [MacBook01:~] $ So, it looks like when a new scope is created, a new local copy of i is also created and recorded in this new scope, so that when the function is executed at a later time, the "i" is found in those scope chains as 1, 2, 3, 4, 5 respectively. Is this true? (It sounds like a heavy operation). Contrast that with p RUBY_VERSION $foo = [] i = 0 (1..5).each do |i| $foo[i] = lambda { p i } end (1..5).each do |j| $foo[j].call() end This time, the i is defined before entering the loop, so Ruby 1.8.6 will not put this i in the new scope created for the loop block, and therefore when the i is looked up in the scope chain, it always refer to the i that was in the outside scope, and give 5 every time: [MacBook01:~] $ ruby scope2.rb "1.8.6" 5 5 5 5 5 [MacBook01:~] $ I heard that in Ruby 1.9, i will be treated as a local defined for the loop even when there is an i defined earlier? The operation of creating a new scope, creating a new local copy of i each time through the loop seems heavy, as it seems it wouldn't have matter if we are not invoking the functions at a later time. So when the functions don't need to be invoked at a later time, could the interpreter and the compiler to C / Java try to optimize it so that there is not local copy of i each time?

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• Delphi - working with dll's for beginners

  - by doubleu

  Hi there, I'm a total newbie regarding to DLL. And I don't need to creat them I just need to use one. I've read some tutorials, but they weren't as helpful as I hoped. Here's the way I started: I've downloaded the SDK which I need to use (ESTOS Tapi Server). I read in the docs and spotted out the DLL which I need to use, which is the ENetSN.dll, and so I registered it. Next I've used the Dependency Walker to take a look at the DLL - and I was wondering because there are only these functions: DllCanUnloadNow, DllGetClassObject, DllRegisterServer and DllUnregisterServer, and these are not the functions mentioned in the docs. I think I have to call DllGetClassObject to get an object out of the DLL with which I can start to work. Unfortunately the tutorials I found doesn't mentioned how this is done (or I didn't understood it). There are also 3 exmaples delivered for VB and C++, but I wasn't able to 'translate' them into delphi. If somebody knows a tutorial where this is explained or could give me a pointer to the right direcetion, I would be very thankful .

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• What's the best way to transition to MVC coding?

  - by ggfan

  It's been around 5 months since I picked up a PHP book and started coding in PHP. At first, I created all my sites without any organizational plan or MVC. I soon found out that was a pain.. Then I started to read on stackoverflow on how to separate php and html and that's what I have been doing ever since. Ex: profile.php <--this file is HTML,css. I just echo the functions here. profile_functions.php <--this file is mostly PHP. has the functions. This is how I have been separating all my coding so far and now I feel I should move on and start MVC. But the problem is, I never used classes before and suck with them. And since MVC (such as cakephp and codeigniter) is all classes, that can't be good. My question: Is there any good books/sites/articles that teaches you how to code in MVC? I am looking for beginner beginner books :) I just started reading the codeigniter manuel and I think I am going to use that. When I looked at the example MVC, they use different PHP coding. When I start coding in MVC, would I have to learn a "new" way to code? Because right now I am coding in pure basic PHP.

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• C# COM Cross Thread problem

  - by user364676

  Hi, we're developing a software to control a scientific measuring device. it provides a COM-Interface defines serveral functions to set measurement parameters and fires an event when it measured data. in order to test our software, i'm implementing a simulation of that device. the com-object runs a loop which periodically fires the event. another loop in the client app should now setup up the com-simulator using the given functions. i created a class for measuring parameters which will be instanciated when setting up a new measurement. // COM-Object public class MeasurementParams { public double Param1; public double Param2; } public class COM_Sim : ICOMDevice { public MeasurementParams newMeasurement; IClient client; public int NewMeasurement() { newMeasurment = new MeasurementParam(); } public int SetParam1(double val) { // why is newMeasurement null when method is called from client loop newMeasurement.Param1 = val; } void loop() { while(true) { // fire event client.HandleEvent; } } } public class Client : IClient { ICOMDevice server; public int HandleEvent() { // handle this event server.NewMeasurement(); server.SetParam1(0.0); } void loop() { while(true) { // do some stuff... server.NewMeasurement(); server.SetParam1(0.0); } } } both of the loops run in independent threads. when server.NewMeasurement() is called, the object on the server is set to a new instance. but in the next function, the object is null again. do the same when handling the server-event, it works perfectly, because the method runs in the servers thread. how to make it work from client-thread as well. as the client is meant to be working with the real device, i cannot modify the interfaces given by the manufactor. also i need to setup measurements independent from the event-handler, which will be fired not regulary. i assume this problem related to multithreaded-COM behavior but i found nothing on this topic.

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• Objects in JavaScript defined and undefined at the same time (in a FireFox extension)

  - by Alexey Romanov

  I am chasing down a bug in a FireFox extension. I've finally managed to see it for myself (I've only had reports before) and I can't understand how what I saw is possible. One error message from my extension in the Error Console is "gBrowser is not defined". This by itself would be surprising enough, since the overlay is over browser.xul and navigator.xul, and I expect gBrowser to be available from both. Even worse is the actual place where it happens: line 101 of nextplease.js. That is, inside the function isTopLevelDocument, which is only called from onContentLoaded, which is only called from onLoad here: gBrowser.addEventListener(this.loadType, function (event) { nextplease.loadListener.onContentLoaded(event); }, true); So gBrowser is defined in onLoad, but somehow undefined in isTopLevelDocument. When I tried to actually use the extension, I got another error: "nextplease is not defined". The interesting thing is that it happened on lines 853 and 857. That is, inside the functions nextplease.getNextLink = function () { nextplease.getLink(window.content, nextplease.NextPhrasesMap, nextplease.NextImagesMap, nextplease.isNextRegExp, nextplease.NEXT_SEARCH_TYPE); } nextplease.getPrevLink = function () { nextplease.getLink(window.content, nextplease.PrevPhrasesMap, nextplease.PrevImagesMap, nextplease.isPrevRegExp, nextplease.PREV_SEARCH_TYPE); } So nextplease is somehow defined enough to call these functions, but isn't defined inside them. Finally, executing typeof(nextplease) in Execute JS returns "object". Same for gBrowser. How can this happen? Any ideas?

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• Writing fortran robust and "modern" code

  - by Blklight

  In some scientific environments, you often cannot go without FORTRAN as most of the developers only know that idiom, and there is lot of legacy code and related experience. And frankly, there are not many other cross-platform options for high performance programming ( C++ would do the task, but the syntax, zero-starting arrays, and pointers are too much for most engineers ;-) ). I'm a C++ guy but I'm stuck with some F90 projects. So, let's assume a new project must use FORTRAN (F90), but I want to build the most modern software architecture out of it. while being compatible with most "recent" compilers (intel ifort, but also including sun/HP/IBM own compilers) So I'm thinking of imposing: global variable forbidden, no gotos, no jump labels, "implicit none", etc. "object-oriented programming" (modules with datatypes + related subroutines) modular/reusable functions, well documented, reusable libraries assertions/preconditions/invariants (implemented using preprocessor statements) unit tests for all (most) subroutines and "objects" an intense "debug mode" (#ifdef DEBUG) with more checks and all possible Intel compiler checks possible (array bounds, subroutine interfaces, etc.) uniform and enforced legible coding style, using code processing tools C stubs/wrappers for libpthread, libDL (and eventually GPU kernels, etc.) C/C++ implementation of utility functions (strings, file operations, sockets, memory alloc/dealloc reference counting for debug mode, etc.) ( This may all seem "evident" modern programming assumptions, but in a legacy fortran world, most of these are big changes in the typical programmer workflow ) The goal with all that is to have trustworthy, maintainable and modular code. Whereas, in typical fortran, modularity is often not a primary goal, and code is trustworthy only if the original developer was very clever, and the code was not changed since then ! (i'm a bit joking here, but not much) I searched around for references about object-oriented fortran, programming-by-contract (assertions/preconditions/etc.), and found only ugly and outdated documents, syntaxes and papers done by people with no large-scale project involvement, and dead projects. Any good URL, advice, reference paper/books on the subject?

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• Should I go vor Arrays or Objects in PHP in a CouchDB/Ajax app?

  - by karlthorwald

  I find myself converting between array and object all the time in PHP application that uses couchDB and Ajax. Of course I am also converting objects to JSON and back (for sometimes couchdb but mostly Ajax), but this is not so much disturbing my workflow. At the present I have php objects that are returned by the CouchDB modules I use and on the other hand I have the old habbit to return arrays like array("error"="not found","data"=$dataObj) from my functions. This leads to a mixed occurence of real php objects and nested arrays and I cast with (object) or (array) if necessary. The worst thing is that I know more or less by heart what a function returns, but not what type (array or object), so I often run into type errors. My plan is now to always cast arrays to objects before returning from a function. Of course this implies a lot of refactoring. Is this the right way to go? What about the conversion overhead? Other ideas or tips? Edit: Kenaniah's answer suggests I should go the other way, this would mean I'd cast everything to arrays. And for all the Ajax / JSON stuff and also for CouchDB I would use $myarray = json_decode($json_data,$assoc = false) Even more work to change all the CouchDB and Ajax functions but in the end I have better code.

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• setInterval works only the first time

  - by Neil

  Hi, I am trying to use setTimer to animate a slide show using straightforward jQuery. I provide the user with a button (in the form of a "DIV" with a button background image) that he clicks to start the show and which then turns into a pause button. The slides are supposed to change every 3 seconds. Here is the relevant code: playLink = $('<div id="lbPlayLink" />').click(function(){ $(playLink).hide(); $(pauseLink).show(); slideInterval = setInterval(function(){next()}, 3000) })[0]; pauseLink = $('<div id="lbPauseLink" />').click(function(){ $(playLink).show(); $(pauseLink).hide(); clearInterval(slideInterval); }).hide()[0]; The next() function call does the work of replacing the slide with the next one. I have checked out this function and it works perfectly if I call it directly (synchronously), however, when it gets called asonchronously by the "setInterval", it works fine the first time (3 seconds after I click on the button), but is never called again, even though it should be called 3 seconds later. I know it's never called as I put an "alert" call at the beginning and end of the function. If I replace the "next()" call in the "setInterval" by "alert('test')" then I can see the setInterval is doing what it is supposed to. I can't for the life of me see why "alert()" is OK but "next()" isn't, unless it has something to do with "scope" of functions, but in that case why does it work the first time? I've tried debugging the code with firebug, but it can't really help with timeout functions like this. Neither Firefox nor IE8 show any error messages. I've looked through the various posts here and elsewhere on setInterval, but can't see anything relevant that I haven't tried already. I've been experimenting now for about 3 hours and it's doing my head in. Can anyone suggest what I can try next? Thanks in advance Neil

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• Complex derived attributes in Django models

  - by rabidpebble

  What I want to do is implement submission scoring for a site with users voting on the content, much like in e.g. reddit (see the 'hot' function in http://code.reddit.com/browser/sql/functions.sql). My submission model currently keeps track of up and down vote totals. Currently, when a user votes I create and save a related Vote object and then use F() expressions to update the Submission object's voting totals. The problem is that I want to update the score for the submission at the same time, but F() expressions are limited to only simple operations (it's missing support for log(), date_part(), sign() etc.) From my limited experience with Django I can see 4 options here: extend F() somehow (haven't looked at the code yet) to support the missing SQL functions; this is my preferred option and seems to fit within the Django framework the best define a scoring function (much like reddit's 'hot' function) in my database, and have Django use the value of that function for the value of the score field; as far as I can tell, #2 is not possible wrap my two step voting process in a suitably isolated transaction so that I can calculate the voting totals in Python and then update the Submission's voting totals without fear that another vote against the submission could be added/changed in the meantime; I'm hesitant to take this route because it seems overly complex - what is a "suitably isolated transaction" in this case anyway? use raw SQL; I would prefer to avoid this entirely -- what's the point of an ORM if I have to revert to SQL for such a common use case as this! (Note that this coming from somebody who loves sprocs, but is using Django for ease of development.) Before I embark on this mission to extend F() (which I'm not sure is even possible), am I about to reinvent the wheel? Is there a more standard way to do this? It seems like such a common use case and yet in an hour of searching I have yet to find a common solution...

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• Python3 and ftplib uploading files

  - by Teifion

  My python2 script uploads files nicely using this method but python3 is presenting problems and I'm stuck as to where to go next (googling hasn't helped). from ftplib import FTP ftp = FTP(ftp_host, ftp_user, ftp_pass) ftp.storbinary('STOR myfile.txt', open('myfile.txt')) The error I get is Traceback (most recent call last): File "/Library/WebServer/CGI-Executables/rob3/functions/cli_f.py", line 12, in upload ftp.storlines('STOR myfile.txt', open('myfile.txt')) File "/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/ftplib.py", line 454, in storbinary conn.sendall(buf) TypeError: must be bytes or buffer, not str I tried altering the code to from ftplib import FTP ftp = FTP(ftp_host, ftp_user, ftp_pass) ftp.storbinary('STOR myfile.txt'.encode('utf-8'), open('myfile.txt')) But instead I got this Traceback (most recent call last): File "/Library/WebServer/CGI-Executables/rob3/functions/cli_f.py", line 12, in upload ftp.storbinary('STOR myfile.txt'.encode('utf-8'), open('myfile.txt')) File "/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/ftplib.py", line 450, in storbinary conn = self.transfercmd(cmd) File "/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/ftplib.py", line 358, in transfercmd return self.ntransfercmd(cmd, rest)[0] File "/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/ftplib.py", line 329, in ntransfercmd resp = self.sendcmd(cmd) File "/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/ftplib.py", line 244, in sendcmd self.putcmd(cmd) File "/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/ftplib.py", line 179, in putcmd self.putline(line) File "/Library/Frameworks/Python.framework/Versions/3.1/lib/python3.1/ftplib.py", line 172, in putline line = line + CRLF TypeError: can't concat bytes to str Can anybody point me in the right direction

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• What is the rationale to non allow overloading of C++ conversions operator with non-member functio

  - by Vicente Botet Escriba

  C++0x has added explicit conversion operators, but they must always be defined as members of the Source class. The same applies to the assignment operator, it must be defined on the Target class. When the Source and Target classes of the needed conversion are independent of each other, neither the Source can define a conversion operator, neither the Target can define a constructor from a Source. Usually we get it by defining a specific function such as Target ConvertToTarget(Source& v); If C++0x allowed to overload conversion operator by non member functions we could for example define the conversion implicitly or explicitly between unrelated types. template < typename To, typename From operator To(const From& val); For example we could specialize the conversion from chrono::time_point to posix_time::ptime as follows template < class Clock, class Duration operator boost::posix_time::ptime( const boost::chrono::time_point& from) { using namespace boost; typedef chrono::time_point time_point_t; typedef chrono::nanoseconds duration_t; typedef duration_t::rep rep_t; rep_t d = chrono::duration_cast( from.time_since_epoch()).count(); rep_t sec = d/1000000000; rep_t nsec = d%1000000000; return posix_time::from_time_t(0)+ posix_time::seconds(static_cast(sec))+ posix_time::nanoseconds(nsec); } And use the conversion as any other conversion. So the question is: What is the rationale to non allow overloading of C++ conversions operator with non-member functions?

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• Haskell math performance

  - by Travis Brown

  I'm in the middle of porting David Blei's original C implementation of Latent Dirichlet Allocation to Haskell, and I'm trying to decide whether to leave some of the low-level stuff in C. The following function is one example—it's an approximation of the second derivative of lgamma: double trigamma(double x) { double p; int i; x=x+6; p=1/(x*x); p=(((((0.075757575757576*p-0.033333333333333)*p+0.0238095238095238) *p-0.033333333333333)*p+0.166666666666667)*p+1)/x+0.5*p; for (i=0; i<6 ;i++) { x=x-1; p=1/(x*x)+p; } return(p); } I've translated this into more or less idiomatic Haskell as follows: trigamma :: Double -> Double trigamma x = snd $ last $ take 7 $ iterate next (x' - 1, p') where x' = x + 6 p = 1 / x' ^ 2 p' = p / 2 + c / x' c = foldr1 (\a b -> (a + b * p)) [1, 1/6, -1/30, 1/42, -1/30, 5/66] next (x, p) = (x - 1, 1 / x ^ 2 + p) The problem is that when I run both through Criterion, my Haskell version is six or seven times slower (I'm compiling with -O2 on GHC 6.12.1). Some similar functions are even worse. I know practically nothing about Haskell performance, and I'm not terribly interested in digging through Core or anything like that, since I can always just call the handful of math-intensive C functions through FFI. But I'm curious about whether there's low-hanging fruit that I'm missing—some kind of extension or library or annotation that I could use to speed up this numeric stuff without making it too ugly.

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• Nusphere PHPEd: PHP Function Hints Lost Arguments?

  - by Eli

  Hi All, My PHPEd suddenly stopped showing arguments and arg order in the hints, and now just shows a basic description of the function. Before I go digging around in the config files, has anyone else had this problem? Thanks! Edit: Sorry, I may not have been entirely clear on this. There is no problem with my own classes, only with the actual php functions. Example: How it used to work: I type a PHP function, say strpos. As soon as I type the '(' at the end of it, I get the little yellow box, showing something like this: int strpos ( string $haystack , mixed $needle [, int $offset=0 ] ) with the first argument bold. If I type it, and then a comma, it bolds the second arg, and so on. This is really nice, since PHP functions are a bit scrambled as far as argument order, and I don't have to look them up every time. How it works now: I type a php function, say strpos. As soon as I type the '(' at the end of it, I get the little yellow box. It says something like "strpos - Returns the numeric position of the first occurrence of needle in the haystack string." There are no arguments shown, which makes the little box basically worthless - I know what strpos does, I just want a reminder of the argument order. I think this may be a problem with the included PHPDoc, which I never use, but may be the source of the data for the hint box. I did recently upgrade to 5.6, but ended up removing it and restoring 5.2. I installed to a different folder, and uninstalled from there, but it may have overwritten something in the original folder? I'm using v5.2 (5220). Thanks!

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• What am i doing wrong

  - by Erik Sapir

  I have the following code. I need B class to have a min priority queue of AToTime objects. AToTime have operator, and yet i receive error telling me than there is no operator matching the operands... #include <queue> #include <functional> using namespace std; class B{ //public functions public: B(); virtual ~B(); //private members private: log4cxx::LoggerPtr m_logger; class AToTime { //public functions public: AToTime(const ACE_Time_Value& time, const APtr a) : m_time(time), m_a(a){} bool operator >(const AToTime& other) { return m_time > other.m_time; } //public members - no point using any private members here public: ACE_Time_Value m_time; APtr m_a; }; priority_queue<AToTime, vector<AToTime>, greater<AToTime> > m_myMinHeap; };

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• subtotals in columns usind reshape2 in R

  - by user1043144

  I have spent some time now learning RESHAPE2 and plyr but I still do not get it. This time I have a problem with (a) subtotals and (b) passing different aggregate functions . Here an example using data from the excellent tutorial on the blog of mrdwab http://news.mrdwab.com/ # libraries library(plyr) library(reshape2) # get data and add few more variables book.sales = read.csv("http://news.mrdwab.com/data-booksales") book.sales$Stock = book.sales$Quantity + 10 book.sales$SubjCat[(book.sales$Subject == 'Economics') | (book.sales$Subject == 'Management') ] <- '1_EconSciences' book.sales$SubjCat[book.sales$Subject %in% c('Anthropology', 'Politics', 'Sociology') ] <- '2_SocSciences' book.sales$SubjCat[book.sales$Subject %in% c('Communication', 'Fiction', 'History', 'Research', 'Statistics') ] <- '3_other' # to get to my starting dataframe (close to the project I am working on) book.sales1 <- ddply(book.sales, c('Region', 'Representative', 'SubjCat', 'Subject', 'Publisher'), summarize, Stock = sum(Stock), Sold = sum(Quantity), Ratio = round((100 * sum(Quantity)/ sum(Stock)), digits = 1)) #melt it m.book.sales = melt(data = book.sales1, id.vars = c('Region', 'Representative', 'SubjCat', 'Subject', 'Publisher'), measured.vars = c('Stock', 'Sold', 'Ratio')) # cast it Tab1 <- dcast(data = m.book.sales, formula = Region + Representative ~ Publisher + variable, fun.aggregate = sum, margins = c('Region', 'Representative')) Now my questions : I have been able to add the subtotals in rows. But is it possible also to add margins in the columns. Say for example, Totals of Stock for one Publisher ? Sorry I meant to say example total sold for all publishers There is a problem with the columns with “ratio”. How can I get “mean” instead of “sum” for this variable ? P.S: I have seen some examples using reshape. Will you recommend to use it instead of reshape2 (which seems not to include the functionalities of two functions).

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• Multiple WCF calls for a single ASP.NET page load

  - by Rodney Burton

  I have an existing asp.net web application I am redesigning to use a service architecture. I have the beginnings of an WCF service which I am able to call and perform functions with no problems. As far as updating data, it all makes sense. For example, I have a button that says Submit Order, it sends the data to the service, which does the processing. Here's my concern: If I have an ASP.NET page that shows me a list of orders (View Orders page), and at the top I have a bunch of drop down lists for order types, and other search criteria which is populated by querying different tables from the database (lookup tables, etc). I am hoping to eventually completely decouple the web application from the DB, and use data contracts to pass information between the BLL, the SOA, and the web app. With that said, how can I reduce the # of WCF calls needed to load my "View Orders" page? I would need to make 1 call get the list of orders, and 1 call for each drop down list, etc because those are populated by individual functions in my BLL. Is it good architecture to create a web service method that returns back a specialized data contract that consists of everything you would need to display a View Orders page, in 1 shot? Something like this pseudocode: public class ViewOrderPageDTO { public OrderDTO[] Orders { get; set; } public OrderTypesDTO[] OrderTypes { get; set; } public OrderStatusesDTO[] OrderStatuses { get; set; } public CustomerListDTO[] CustomerList { get; set; } } Or is it better practice in the page_load event to make 5 or 6 or even 15 individual calls to the SOA to get the data needed to load the page? Therefore, bypassing the need for specialized wcf methods or DTO's that conglomerate other DTO? Thanks for your input and suggestions.

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• performance of large number calculations in python (python 2.7.3 and .net 4.0)

  - by g36

  There is a lot of general questions about python performance in comparison to other languages. I've got more specific example: There are two simple functions wrote in python an c#, both checking if int number is prime. python: import time def is_prime(n): num =n/2 while num >1: if n % num ==0: return 0 num-=1 return 1 start = time.clock() probably_prime = is_prime(2147483629) elapsed = (time.clock() - start) print 'time : '+str(elapsed) and C#: using System.Diagnostics; public static bool IsPrime(int n) { int num = n/2; while(num >1) { if(n%num ==0) { return false; } num-=1; } return true; } Stopwatch sw = new Stopwatch(); sw.Start(); bool result = Functions.IsPrime(2147483629); sw.Stop(); Console.WriteLine("time: {0}", sw.Elapsed); And times ( which are surprise for me as a begginer in python:)): Python: 121s; c#: 6s Could You explain where does this big diffrence come from ?

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