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  • Scope of "library" methods

    - by JS
    Hello, I'm apparently laboring under a poor understanding of Python scoping. Perhaps you can help. Background: I'm using the 'if name in "main"' construct to perform "self-tests" in my module(s). Each self test makes calls to the various public methods and prints their results for visual checking as I develop the modules. To keep things "purdy" and manageable, I've created a small method to simplify the testing of method calls: def pprint_vars(var_in): print("%s = '%s'" % (var_in, eval(var_in))) Calling pprint_vars with: pprint_vars('some_variable_name') prints: some_variable_name = 'foo' All fine and good. Problem statement: Not happy to just KISS, I had the brain-drizzle to move my handy-dandy 'pprint_vars' method into a separate file named 'debug_tools.py' and simply import 'debug_tools' whenever I wanted access to 'pprint_vars'. Here's where things fall apart. I would expect import debug_tools foo = bar debug_tools.pprint_vars('foo') to continue working its magic and print: foo = 'bar' Instead, it greets me with: NameError: name 'some_var' is not defined Irrational belief: I believed (apparently mistakenly) that import puts imported methods (more or less) "inline" with the code, and thus the variable scoping rules would remain similar to if the method were defined inline. Plea for help: Can someone please correct my (mis)understanding of scoping regards imports? Thanks, JS

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  • JavaScript onchange, onblur, and focus weirdness in Firefox

    - by typoknig
    On my form I have a discount field that accepts a dollar amount to be taken off of the total bill (HTML generated in PHP): echo "<input id=\"discount\" class=\"text\" type=\"text\" name=\"discount\" onkeypress=\"return currency(this, event)\" onchange=\"currency_format(this)\" onfocus=\"on_focus(this)\" onblur=\"on_blur(this); calculate_bill()\"/><br/><br/>\n"; The JavaScript function calculate_bill calculates the bill and takes off the discount amount as long as the discount amount is less than the total bill: if(discount != ''){ if(discount - 0.01 > total_bill){ window.alert('Discount Cannot Be Greater Than Total Bill'); document.form.discount.focus(); } else{ total_bill -= discount; } } The problem is that even that when the discount is more than the total bill focus is not being returned to the discount field. I have tried calling the calculate_bill function with onchange but neither IE or Firefox will return focus to the discount field when I do it like that. When I call calculate_bill with onblur it works in IE, but still does not work in Firefox. I have attempted to use a confirmation box instead of an alert box as well, but that didn't work either (plus I don't want two buttons, I only an "OK" button). How can I ensure focus is returned to the discount field after a user has left that field by clicking on another field or tabbing IF the discount amount is larger than the total bill?

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  • Trouble with custom WPF Panel-derived class

    - by chaiguy
    I'm trying to write a custom Panel class for WPF, by overriding MeasureOverride and ArrangeOverride but, while it's mostly working I'm experiencing one strange problem I can't explain. In particular, after I call Arrange on my child items in ArrangeOverride after figuring out what their sizes should be, they aren't sizing to the size I give to them, and appear to be sizing to the size passed to their Measure method inside MeasureOverride. Am I missing something in how this system is supposed to work? My understanding is that calling Measure simply causes the child to evaluate its DesiredSize based on the supplied availableSize, and shouldn't affect its actual final size. Here is my full code (the Panel, btw, is intended to arrange children in the most space-efficient manner, giving less space to rows that don't need it and splitting remaining space up evenly among the rest--it currently only supports vertical orientation but I plan on adding horizontal once I get it working properly): protected override Size MeasureOverride( Size availableSize ) { foreach ( UIElement child in Children ) child.Measure( availableSize ); return availableSize; } protected override System.Windows.Size ArrangeOverride( System.Windows.Size finalSize ) { double extraSpace = 0.0; var sortedChildren = Children.Cast<UIElement>().OrderBy<UIElement, double>( new Func<UIElement, double>( delegate( UIElement child ) { return child.DesiredSize.Height; } ) ); double remainingSpace = finalSize.Height; double normalSpace = 0.0; int remainingChildren = Children.Count; foreach ( UIElement child in sortedChildren ) { normalSpace = remainingSpace / remainingChildren; if ( child.DesiredSize.Height < normalSpace ) // if == there would be no point continuing as there would be no remaining space remainingSpace -= child.DesiredSize.Height; else { remainingSpace = 0; break; } remainingChildren--; } extraSpace = remainingSpace / Children.Count; double offset = 0.0; foreach ( UIElement child in Children ) { //child.Measure( new Size( finalSize.Width, normalSpace ) ); double value = Math.Min( child.DesiredSize.Height, normalSpace ) + extraSpace; child.Arrange( new Rect( 0, offset, finalSize.Width, value ) ); offset += value; } return finalSize; }

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  • jQuery arrays - newbie needs a kick start

    - by Jonny Wood
    I've only really started using this site and alredy I am very impressed by the community here! This is my third question in less than three days. Hopefully I'll be able to start answering questions soon instead of just asking them! I'm fairly new to jQuery and can't find a decent tutorial on Arrays. I'd like to be able to create an array that targets several ID's on my page and performs the same effect for each. For example I have tabs set up with the following: $('.tabs div.tab').hide(); $('.tabs div:first').show(); $('.tabs ul li:first a').addClass('current'); $('.tabs ul li a').click(function(){ $('.tabs ul li a').removeClass('current'); $(this).addClass('current'); var currentTab = $(this).attr('href'); $('.tabs div.tab').hide(); $(currentTab).show(); return false; }); I've used the class .tag to target the tabs as there are several sets on the same page, but I've heard jQuery works much faster when targetting ID's How would I add an array to the above code to target 4 different ID's? I've looked at var myArray = new Array('#id1', 'id2', 'id3', 'id4'); And also var myValues = [ '#id1', 'id2', 'id3', 'id4' ]; Which is correct and how do I then use the array in the code for my tabs...?

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  • Linux time sample based profiler.

    - by Caspin
    short version: Is there a good time based sampling profiler for Linux? long version: I generally use OProfile to optimize my applications. I recently found a shortcoming that has me wondering. The problem was a tight loop spawning c++filt to demangle a c++ name. I only stumbled upon the code by accident while chasing down another bottleneck. The OProfile didn't show anything unusual about the code so I almost ignored it but my code sense told me to optimize the call and see what happened. I changed the popen of c++filt to abi::__cxa_demangle. The runtime went from more than a minute to a little over a second. About a x60 speed up. Is there a way I could have configured OProfile to flag the popen call? As the profile data sits now OProfile thinks the bottle neck was the heap and std::string calls (which BTW once optimized dropped the runtime to less than a second, more than x2 speed up). Here is my OProfile configuration: $ sudo opcontrol --status Daemon not running Event 0: CPU_CLK_UNHALTED:90000:0:1:1 Separate options: library vmlinux file: none Image filter: /path/to/excutable Call-graph depth: 7 Buffer size: 65536 Is there another profiler for Linux that could have found the bottleneck? I suspect the issue is that OProfile only logs its samples to the currently running process. I'd like it to always log its samples to the process I'm profiling. So if the process is currently switched out (blocking on IO or a popen call) OProfile would just place its sample at the blocked call. If I can't fix this, OProfile will only be useful when the executable is pushing near 100% CPU. It can't help with executables that that have inefficient blocking calls.

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  • Namespace constants and use as

    - by GordonM
    I'm having some problems with using constants from a namespace. If I define the constant and try to use as it, PHP seems unable to find it. For example, in my file with the constants I have code along the lines of the following: namespace \my\namespace\for\constants; const DS = DIRECTORY_SEPARATOR; Then in the consuming file I have: namespace \some\other\namespace; use \my\namespace\for\constants\DS as DS; echo (realpath (DS . 'usr' . DS 'local')); However, instead of echoing '/usr/local' as expected I get the following notice and an empty string. Notice: Use of undefined constant DS - assumed 'DS' If I change the code as follows: use \my\namespace\for\constants as cns; echo (realpath (cns\DS . 'usr' . cns\DS 'local')); I get the expected result, but it's obviously quite a bit less convenient than just being able to pull the constants in directly. You can alias a class/interface/trait in a namespace, are you not able to alias a constant too? If you can do it, then how?

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  • Alternatives to the Entity Framework for Serving/Consuming an OData Interface

    - by Egahn
    I'm researching how to set up an OData interface to our database. I would like to be able to pull/query data from our DB into Excel, as a start. Eventually I would like to have Excel run queries and pull data over HTTP from a remote client, including authentication, etc. I've set up a working (rickety) prototype so far, using the ADO.NET Entity Data Model wizard in Visual Studio, and VSTO to create a test Excel worksheet with a button to pull from that ADO.NET interface. This works OK so far, and I can query the DB using Linq through the entities/objects that are created by the ADO.NET EDM wizard. However, I have started to run into some problems with this approach. I've been finding the Entity Framework difficult to work with (and in fact, also difficult to research solutions to, as there's a lot of chaff out there regarding it and older versions of it). An example of this is my being unable to figure out how to set the SQL command timeout (as opposed to the HTTP request timeout) on the DataServiceContext object that the wizard generates for my schema, but that's not the point of my question. The real question I have is, if I want to use OData as my interface standard, am I stuck with the Entity Framework? Are there any other solutions out there (preferably open source) which can set up, serve and consume an OData interface, and are easier to work with and less bloated than the Entity Framework? I have seen mention of NHibernate as an alternative, but most of the comparison threads I've seen are a few years old. Are there any other alternatives out there now? Thanks very much!

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  • DataGridView with row-specific DataGridViewComboBoxColumn contents in C# Windows Forms 3.5

    - by XXXXX
    So I have something like the following data structure (constructors omitted) class Child { public string Name { get; set; } public int Age { get; set; } } class Parent { public string Name { get; set; } public List <Child> Children { get; private set; } // never null; list never empty public Child FavoriteChild { get; set; } // never null; always a reference to a Child in Children } List < Parent > Parents; What I want to do is show a DataGridView where each row is a Parent from Parent list. Each row should have two columns: a text box showing the parent's name and a DataGridViewComboBoxColumn containing that parent's children, from which the user can select the parent's favorite child. I suppose I could do the whole thing manually, but I'd like to do all this with more-or-less standard Data Binding. It's easy enough to bind the DataGridView to the list of parents, and easy enough to bind the selected child to the FavoriteChild property. The part that's giving me difficulty is that it looks like the Combo Box column wants to bind to one data source for all the combo-box's contents on all rows. I'd like each instance of the combo box to bind to the list of each parent's children. I'm fairly new to C#/Windows Forms, so I may well be missing something obvious. Or it could be that "you can't get there from here." It's not too tough to make a separate list of all the children and filter it by parent; I'm looking into that possibility right now. Is this feasible, or is there a better way?

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  • Is there a way to increase performance on my simple textfilter?

    - by djerry
    Hey guys, I'm writing a filter that will pick out items. I have a list of Objects. The objects contain a number, name and some other irrelevant items. At the moment, the list contains 200 items. When typing in a textbox, i'm looking if the string matches a part of the number/name of the objects in the list. If so, add them to the listbox. Here's the code for my textbox textchanged event : private void txtTelnumber_TextChanged(object sender, TextChangedEventArgs e) { lstOverview.Items.Clear(); string data = ""; foreach (ucTelListItem telList in _allUsers) { data = telList.User.H323 + telList.user.E164; if (data.Contains(txtTelnumber.Text)) lstOverview.Items.Add(telList); } } I sometimes see a little delay when entering a character, especially when i go from 4 records to 200 records (so when i had a filter and 4 records matched, and i backspace and the whole list appears again). My list is a list of usercontrols, cause i found it takes less time to load the usercontrols from a list, then to have to initialize a new usercontrol each time. Can i do something about the code, or is it just adding the usercontrol the listbox that causes the small delay (small delay = <1 sec)? Thanks in advance.

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  • What Javascript graphing package will let me plot points against a user-selected coordinate system?

    - by wes
    My customer has some specific requirements for a graph to show in our web app. We use HighCharts elsewhere in the app for more traditional graphing, but it doesn't seem to work for this situation. Their requirements: Allow the user to select a background image, set the scale and origin of the coordinate system. We'll graph our points against the user-defined coordinates. Points can be color coded Mouse-over boxes show more detail about the points Support for zooming and panning, scaling the background appropriately Less importantly: Support for drawing vectors off the points Some of this seems basic, but looking around at different graph packages, I was unable to find any with an example of this kind of usage. I've entertained the thought of just hacking it together in canvas myself, but I've never worked with canvas before so I don't think it would be cost effective. The basics of plotting points with a scaled coordinate system against an image background wouldn't be too hard, but the mouse-over details, zooming and panning sound much more daunting to me. More info: Right now we use jQuery, HighCharts, and ExtJS for our app. We tried flot in the past but switched to HighCharts after flot didn't meet our needs.

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  • Dynamic Array traversal in PHP

    - by Kristoffer Bohmann
    I want to build a hierarchy from a one-dimensional array and can (almost) do so with a more or less hardcoded code. How can I make the code dynamic? Perhaps with while(isset($array[$key])) { ... }? Or, with an extra function? Like this: $out = my_extra_traverse_function($array,$key); function array_traverse($array,$key=NULL) { $out = (string) $key; $out = $array[$key] . "/" . $out; $key = $array[$key]; $out = $array[$key] ? $array[$key] . "/" . $out : ""; $key = $array[$key]; $out = $array[$key] ? $array[$key] . "/" . $out : ""; $key = $array[$key]; $out = $array[$key] ? $array[$key] . "/" . $out : ""; return $out; } $a = Array(102=>101, 103=>102, 105=>107, 109=>105, 111=>109, 104=>111); echo array_traverse($a,104); Output: 107/105/109/111/104

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  • help with mysql triggers (checking values before insert)

    - by user332817
    hi I'm quite new to mysql and I'm trying to figure out how to use triggers. what I'm trying to do: I have 2 tables, max and sub_max, when I insert a new row to sub_max I want to check if the SUM of the values with the same foreign_key as the new row are less than the value in the max table. I think this sounds confusing so here are my tables: CREATE TABLE max( number INT , MaxAmount integer NOT NULL) CREATE TABLE sub_max( sub_number INT , sub_MaxAmount integer NOT NULL, number INT, FOREIGN KEY ( number ) REFERENCES max( number )) and here is my code for the trigger, I know the syntax is off but this is the best I could do from looking up tutorials. CREATE TRIGGER maxallowed after insert on submax FOR EACH ROW BEGIN DECLARE submax integer; DECLARE maxmax integer; submax = select sum(sub_MaxAmount) from sub_max where sub_number = new.sub_number; submax = submax + new. sub_MaxAmount; maxmax = select MaxAmount from max where number = new.number ; if max>maxmax rollback? END I wanted to know if I'm doing this remotely correctly. Thanks in advance.

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  • Load SQL query result data into cache in advance

    - by Marc
    I have the following situation: .net 3.5 WinForm client app accessing SQL Server 2008 Some queries returning relatively big amount of data are used quite often by a form Users are using local SQL Express and restarting their machines at least daily Other users are working remotely over slow network connections The problem is that after a restart, the first time users open this form the queries are extremely slow and take more or less 15s on a fast machine to execute. Afterwards the same queries take only 3s. Of course this comes from the fact that no data is cached and must be loaded from disk first. My question: Would it be possible to force the loading of the required data in advance into SQL Server cache? Note My first idea was to execute the queries in a background worker when the application starts, so that when the user starts the form the queries will already be cached and execute fast directly. I however don't want to load the result of the queries over to the client as some users are working remotely or have otherwise slow networks. So I thought just executing the queries from a stored procedure and putting the results into temporary tables so that nothing would be returned. Turned out that some of the result sets are using dynamic columns so I couldn't create the corresponding temp tables and thus this isn't a solution. Do you happen to have any other idea?

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  • Using Python to get a CSV output for the following example.

    - by Az
    Hi there, I'm back again with my ongoing saga of Student-Project Allocation questions. Thanks to Moron (who does not match his namesake) I've got a bit of direction for an evaluation portion of my project. Going with the idea of the Assignment Problem and Hungarian Algorithm I would like to express my data in the form of a .csv file which would end up looking like this in spreadsheet form. This is based on the structure I saw here. | | Project 1 | Project 2 | Project 3 | |----------|-----------|-----------|-----------| |Student1 | | 2 | 1 | |----------|-----------|-----------|-----------| |Student2 | 1 | 2 | 3 | |----------|-----------|-----------|-----------| |Student3 | 1 | 3 | 2 | |----------|-----------|-----------|-----------| To make it less cryptic: the rows are the Students/Agents and the columns represent Projects/Task. Obviously ONE project can be assigned to ONE student. That, in short, is what my project is about. The fields represent the preference weights the students have placed upon the projects (ranging from 1 to 10). If blank, that student does not want that project and there's no chance of him/her being assigned such. Anyway, my data is stored within dictionaries. Specifically the students and projects dictionaries such that: students[student_id] = Student(student_id, student_name, alloc_proj, alloc_proj_rank, preferences) where preferences is in the form of a dictionary such that preferences[rank] = {project_id} and projects[project_id] = Project(project_id, project_name) I'm aware that sorted(students.keys()) will give me a sorted list of all the student IDs which will populate the row labels and sorted(projects.keys()) will give me the list I need to populate the column labels. Thus for each student, I'd go into their preferences dictionary and match the applicable projects to ranks. I can do that much. Where I'm failing is understanding how to create a .csv file. Any help, pointers or good tutorials will be highly appreciated.

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  • Validating Time & Date To Be At Least A Certain Amount Of Time In The Future

    - by MJH
    I've built a reservation form for a taxi company which works fine, but I'm having an issue with users making reservations that are due too soon in the future. Since the entire form is kind of long, I first want to make sure the user is not trying to make a reservation for less than an hour ahead of time, without them having to fill out the whole form. This is what I have come up with so far, but it's just not working: <?php //Set local time zone. date_default_timezone_set('America/New_York'); //Get current date and time. $current_time = date('Y-m-d H:i:s'); //Set reservation time variable $res_datetime = $_POST['res_datetime']; //Set event time. $event_time = strtotime($res_datetime); ?> <!doctype html> <html> <head> <meta charset="utf-8"> <title>Check Date and Time</title> </head> <?php //Check to be sure reservation time is at least one hour in the future. if (($current_time - $event_time) <= (3600)) { echo "You must make a reservation at least one hour ahead of time."; } ?> <form name="datetime" action="" method="post"> <input name="res_datetime" type="datetime-local" id="res_datetime"> <input type="submit"> </form> <body> </body> </html> How can I create a validation check to make sure the date and time of the reservation is at least one hour ahead of time?

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  • P0ST variables to web server?

    - by OverTheRainbow
    Hello I've been trying several things from Google to POST data to a web server, but none of them work: I'm still stuck at how to convert the variables into the request, considering that the second variable is an SQL query so it has spaces. Does someone know the correct way to use a WebClient to POST data? I'd rather use WebClient because it requires less code than HttpWebRequest/HttpWebResponse. Here's what I tried so far: Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim wc = New WebClient() 'convert data wc.Headers.Add("Content-Type", "application/x-www-form-urlencoded") Dim postData = String.Format("db={0}&query={1}", _ HttpUtility.UrlEncode("books.sqlite"), _ HttpUtility.UrlEncode("SELECT id,title FROM boooks")) 'Dim bytArguments As Byte() = Encoding.ASCII.GetBytes("db=books.sqlite|query=SELECT * FROM books") 'POST query Dim bytRetData As Byte() = wc.UploadData("http://localhost:9999/get", "POST", postData) RichTextBox1.Text = Encoding.ASCII.GetString(bytRetData) Exit Sub Dim client = New WebClient() Dim nv As New Collection nv.Add("db", "books.sqlite") nv.Add("query", "SELECT id,title FROM books") Dim address As New Uri("http://localhost:9999/get") 'Dim bytRetData As Byte() = client.UploadValues(address, "POST", nv) RichTextBox1.Text = Encoding.ASCII.GetString(bytRetData) Exit Sub 'Dim wc As New WebClient() 'convert data wc.Headers.Add("Content-Type", "application/x-www-form-urlencoded") Dim bytArguments As Byte() = Encoding.ASCII.GetBytes("db=books.sqlite|query=SELECT * FROM books") 'POST query 'Dim bytRetData As Byte() = wc.UploadData("http://localhost:9999/get", "POST", bytArguments) RichTextBox1.Text = Encoding.ASCII.GetString(bytRetData) Exit Sub End Sub Thank you.

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  • C++0x rvalue references and temporaries

    - by Doug
    (I asked a variation of this question on comp.std.c++ but didn't get an answer.) Why does the call to f(arg) in this code call the const ref overload of f? void f(const std::string &); //less efficient void f(std::string &&); //more efficient void g(const char * arg) { f(arg); } My intuition says that the f(string &&) overload should be chosen, because arg needs to be converted to a temporary no matter what, and the temporary matches the rvalue reference better than the lvalue reference. This is not what happens in GCC and MSVC. In at least G++ and MSVC, any lvalue does not bind to an rvalue reference argument, even if there is an intermediate temporary created. Indeed, if the const ref overload isn't present, the compilers diagnose an error. However, writing f(arg + 0) or f(std::string(arg)) does choose the rvalue reference overload as you would expect. From my reading of the C++0x standard, it seems like the implicit conversion of a const char * to a string should be considered when considering if f(string &&) is viable, just as when passing a const lvalue ref arguments. Section 13.3 (overload resolution) doesn't differentiate between rvalue refs and const references in too many places. Also, it seems that the rule that prevents lvalues from binding to rvalue references (13.3.3.1.4/3) shouldn't apply if there's an intermediate temporary - after all, it's perfectly safe to move from the temporary. Is this: Me misreading/misunderstand the standard, where the implemented behavior is the intended behavior, and there's some good reason why my example should behave the way it does? A mistake that the compiler vendors have somehow all made? Or a mistake based on common implementation strategies? Or a mistake in e.g. GCC (where this lvalue/rvalue reference binding rule was first implemented), that was copied by other vendors? A defect in the standard, or an unintended consequence, or something that should be clarified?

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  • PHP Object References in Frameworks

    - by bigstylee
    Before I dive into the disscusion part a quick question; Is there a method to determine if a variable is a reference to another variable/object? For example $foo = 'Hello World'; $bar = &$foo; echo (is_reference($bar) ? 'Is reference' : 'Is orginal'; I have been using PHP5 for a few years now (personal use only) and I would say I am moderately reversed on the topic of Object Orientated implementation. However the concept of Model View Controller Framework is fairly new to me. I have looked a number of tutorials and looked at some of the open source frameworks (mainly CodeIgnitor) to get a better understanding how everything fits together. I am starting to appreciate the real benefits of using this type of structure. I am used to implementing object referencing in the following technique. class Foo{ public $var = 'Hello World!'; } class Bar{ public function __construct(){ global $Foo; echo $Foo->var; } } $Foo = new Foo; $Bar = new Bar; I was surprised to see that CodeIgnitor and Yii pass referencs of objects and can be accessed via the following method: $this->load->view('argument') The immediate advantage I can see is a lot less code and more user friendly. But I do wonder if it is more efficient as these frameworks are presumably optimised? Or simply to make the code more user friendly? This was an interesting article Do not use PHP references.

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  • capturing CMD batch file parameter list; write to file for later processing

    - by BobB
    I have written a batch file that is launched as a post processing utility by a program. The batch file reads ~24 parameters supplied by the calling program, stores them into variables, and then writes them to various text files. Since the max input variable in CMD is %9, it's necessary to use the 'shift' command to repeatedly read and store these individually to named variables. Because the program outputs several similar batch files, the result is opening several CMD windows sequentially, assigning variables and writing data files. This ties up the calling program for too long. It occurs to me that I could free up the calling program much faster if maybe there's a way to write a very simple batch file that can write all the command parameters to a text file, where I can process them later. Basically, just grab the parameter list, write it and done. Q: Is there some way to treat an entire series of parameter data as one big text string and write it to one big variable... and then echo the whole big thing to one text file? Then later read the string into %n variables when there's no program waiting to resume? Parameter list is something like 25 - 30 words, less than 200 characters. Sample parameter list: "First Name" "Lastname" "123 Steet Name Way" "Cityname" ST 12345 1004968 06/01/2010 "Firstname+Lastname" 101738 "On Account" 20.67 xy-1z 1 8.95 3.00 1.39 0 0 239 8.95 Items in quotes are processed as string variables. List is space delimited. Any suggestions?

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  • Should java try blocks be scoped as tightly as possible?

    - by isme
    I've been told that there is some overhead in using the Java try-catch mechanism. So, while it is necessary to put methods that throw checked exception within a try block to handle the possible exception, it is good practice performance-wise to limit the size of the try block to contain only those operations that could throw exceptions. I'm not so sure that this is a sensible conclusion. Consider the two implementations below of a function that processes a specified text file. Even if it is true that the first one incurs some unnecessary overhead, I find it much easier to follow. It is less clear where exactly the exceptions come from just from looking at statements, but the comments clearly show which statements are responsible. The second one is much longer and complicated than the first. In particular, the nice line-reading idiom of the first has to be mangled to fit the readLine call into a try block. What is the best practice for handling exceptions in a funcion where multiple exceptions could be thrown in its definition? This one contains all the processing code within the try block: void processFile(File f) { try { // construction of FileReader can throw FileNotFoundException BufferedReader in = new BufferedReader(new FileReader(f)); // call of readLine can throw IOException String line; while ((line = in.readLine()) != null) { process(line); } } catch (FileNotFoundException ex) { handle(ex); } catch (IOException ex) { handle(ex); } } This one contains only the methods that throw exceptions within try blocks: void processFile(File f) { FileReader reader; try { reader = new FileReader(f); } catch (FileNotFoundException ex) { handle(ex); return; } BufferedReader in = new BufferedReader(reader); String line; while (true) { try { line = in.readLine(); } catch (IOException ex) { handle(ex); break; } if (line == null) { break; } process(line); } }

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  • ASP MVC - Routing Required?

    - by evo_9
    I've been reading up on MVC2 which came in VS2010 and it sounds pretty interesting. I'm actually in the middle of a large multi-tenant application project, and have just started coding the UI. I'm considering changing to MVC as I'm not that far along at this point. I have some questions about the Routing capabilities, namely are they required to use MVC or can I more or less ignore Routing? Or do I have to setup a default routing record that will make things work like standard ASPX (as far as routing alone is concerned)? The reason why I don't want to use Routing is because I've already defined a custom URL 'rewrite' mechanism of my own (which fires on session_start). In addition, I'm using jquery and opens-standards for the entire UI, and MVC's aspx overhead-free approach seems like a better fit based on how I've already started to build the application (I am not using viewstate at all, for example). I guess my big concern is whether the routing can be ignored, of if I will have to re-implement my custom URL rewriting to work with MVC, and if that's the case, how would I do that? As a new Routing routine, or stick with the session_start (if that's even possible?). Lastly, I don't want to use anything even remotely 'intelligent/readable' for the url - for a site like StackOverflow, the readability of the URL is a positive, but the opposite is true if it's not a public website like this one. In fact, it would seem to me that the more friendly MVC routing URL (which indirectly show method names) could pose a security risk on a private, non-public website app like I'm developing. For all these reasons I would love to use the lightweight aspects of MVC but skip the Routing entirely - is this possible?

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  • Why does a sub-class class of a class have to be static in order to initialize the sub-class in the

    - by Alex
    So, the question is more or less as I wrote. I understand that it's probably not clear at all so I'll give an example. I have class Tree and in it there is the class Node, and the empty constructor of Tree is written: public class RBTree { private RBNode head; public RBTree(RBNode head,RBTree leftT,RBTree rightT){ this.head=head; this.head.leftT.head.father = head; this.head.rightT.head.father = head; } public RBTree(RBNode head){ this(head,new RBTree(),new RBTree()); } public RBTree(){ this(new RBNode(),null,null); } public class RBNode{ private int value; private boolean isBlack; private RBNode father; private RBTree leftT; private RBTree rightT; } } Eclipse gives me the error: "No enclosing instance of type RBTree is available due to some intermediate constructor invocation" for the "new RBTree()" in the empty constructor. However, if I change the RBNode to be a static class, there is no problem. So why is it working when the class is static. BTW, I found an easy solution for the cunstructor: public RBTree(){ this.head = new RBNode(); } So, I have no idea what is the problem in the first piece of code.

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  • What if you used the wrong language?

    - by HS
    A reply to another question made me remember a project from some years ago when it turned out that Java was not the right tool to use. I typically only learn a new language when I have a problem that it solves better than the ones I already know. [...] Then I write whatever program I wanted to learn that language for in the first place. [...] By the time I've gotten my target program written, I've usually got a decent handle on the language, not to mention any other features it has, and I've got other ideas to use it for. I did just that back then with Java, because the client thought it to be the right language to use (platform independent) and initial evaluation confirmed that. However, much later in the project there were some issue (can't really remember all the details by now). So, the project that started as a nice learning experience turned into a nightmare toward the end. I was at the brink of switching over to my trusted C++ and doing a complete rewrite. The client was not so much of a problem to convince back then, but my supervisor was strongly opposed because of all the work that already went into the Java version. In hindsight, he was right and the project was complete more or less with the intended features kind of working, but it was the project that I am least proud of by now. Long story short: what do you think, when is it too much and the switch to another technology is worthwhile? I personally would estimate the point of no return to be around 50% of the planned effort, but really want to know, if anyone has real experience with such a switch. And to answer the inevitable question: I do not really care, if the technology switched to is proven or another new thing. The latter would basically need more initial scrutiny based on the past experiences in the problematic project.

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  • How to Detect in Windows Registry if user has .Net Framework installed?

    - by Sarah Weinberger
    How do I detect in the Windows Registry if a user has .Net Framework installed? I am not looking for a .Net based solution, as the query is from InnoSetup. I know from reading another post here on Stack Overflow that .Net Framework is an inplace upgrade to 4.0. I already know how to check if a user has version 4.0 installed on the system, namely by checking the following: function FindFramework(): Boolean; var bVer4x0: Boolean; bVer4x0Client: Boolean; bVer4x0Full: Boolean; bSuccess: Boolean; iInstalled: Cardinal; begin Result := False; bVer4x0Client := False; bVer4x0Full := False; bVer4x0 := RegKeyExists(HKLM, 'SOFTWARE\Microsoft\.NETFramework\policy\v4.0'); bSuccess := RegQueryDWordValue(HKLM, 'Software\Microsoft\NET Framework Setup\NDP\v4 \Client', 'Install', iInstalled); if (1 = iInstalled) AND (True = bSuccess) then bVer4x0Client := True; bSuccess := RegQueryDWordValue(HKLM, 'Software\Microsoft\NET Framework Setup\NDP\v4 \Full', 'Install', iInstalled); if (1 = iInstalled) AND (True = bSuccess) then bVer4x0Full := True; if (True = bVer4x0Full) then begin Result := True; end; end; I checked the registry and there is no v4.5 folder, which makes sense if .Net Framework 4.5 is an inplace upgrade. Still, the Control Panel Programs and Features includes the listing. I know that probably "issuing dotNetFx45_Full_setup.exe /q" will have no bad effect if installing on a system that already has version 4.5, but I still would like to not install the upgrade if the upgrade already exists, faster and less problems.

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  • How is a referencing environment generally implemented for closures?

    - by Alexandr Kurilin
    Let's say I have a statically/lexically scoped language with deep binding and I create a closure. The closure will consist of the statements I want executed plus the so called referencing environment, or, to quote this post, the collection of variables which can be used. What does this referencing environment actually look like implementation-wise? I was recently reading about ObjectiveC's implementation of blocks, and the author suggests that behind the scenes you get a copy of all of the variables on the stack and also of all the references to heap objects. The explanation claims that you get a "snapshot" of the referencing environment at the point in time of the closure's creation. Is that more or less what happens, or did I misread that? Is anything done to "freeze" a separate copy of the heap objects, or is it safe to assume that if they get modified between closure creation and the closure executing, the closure will no longer be operating on the original version of the object? If indeed there's copying being made, are there memory usage considerations in situations where one might want to create plenty of closures and store them somewhere? I think that misunderstanding of some of these concepts might lead to tricky issues like the ones Eric Lippert mentions in this blog post. It's interesting because you'd think that it wouldn't make sense to keep a reference to a value type that might be gone by the time the closure is called, but I'm guessing that in C# the compiler will figure out that the variable is needed later and put it into the heap instead. It seems that in most memory-managed languages everything is a reference and thus ObjectiveC is a somewhat unique situation with having to deal with copying what's on the stack.

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