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• Can you explain what's going on in this Ruby code?

  - by samoz

  I'm trying to learn Ruby as well as Ruby on Rails right now. I'm following along with Learning Rails, 1st edition, but I'm having a hard time understanding some of the code. I generally do work in C, C++, or Java, so Ruby is a pretty big change for me. I'm currently stumped with the following block of code for a database migrator: def self.up create_table :entries do |t| t.string :name t.timestamps end end Where is the t variable coming from? What does it actually represent? Is it sort of like the 'i' in a for(i=0;i<5;i++) statement? Also, where is the :entries being defined at? (entries is the name of my controller, but how does this function know about that?)

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• calculate next line numbers

  - by osomanden

  Weird question I guess.. But I am not very math wiz - soo here goes.. I am trying to create a patterne (or variable patterns based on selection) based on x and y numbers (2 rows and 4 columns) and the direction of the counting of x numbers like: 1-2-3-4 5-6-7-8 That one is easy, when number of x-columns is reached, next line and continue x count. But with eg. this one (still 2 rows and 4 columns): 1-2-3-4 8-7-6-5 upsie.. what if it is eg. 3++ rows and still 4 columns? 1-2-3-4 8-7-6-5 9-10-11-12 what would be the formula for this - or other possible variations (teaser for variations): 9-10-11-12 8-7-6-5 1-2-3-4 or reversed

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• Problem with debug watch in Visual Studio with yield return enumerator methods

  - by Stuart

  I have a method which returns an IEnumerable<> which it builds up using the yield return syntax: public IEnumerable<ValidationError> Validate(User user) { if (String.IsNullOrEmpty(user.Name)) { yield return new ValidationError("Name", ValidationErrorType.Required); } [...] yield break; } If I put a breakpoint in the method, I can step over each line, but if I try to use the Watch or Immediate windows to view the value of a variable I get this error: Cannot access a non-static member of outer type '[class name].Validate' via nested type '[class name]' Does anyone know why this is and how I can get around it?

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• filtering elements from list of lists in Python?

  - by user248237

  I want to filter elements from a list of lists, and iterate over the elements of each element using a lambda. For example, given the list: a = [[1,2,3],[4,5,6]] suppose that I want to keep only elements where the sum of the list is greater than N. I tried writing: filter(lambda x, y, z: x + y + z >= N, a) but I get the error: <lambda>() takes exactly 3 arguments (1 given) How can I iterate while assigning values of each element to x, y, and z? Something like zip, but for arbitrarily long lists. thanks, p.s. I know I can write this using: filter(lambda x: sum(x)..., a) but that's not the point, imagine that these were not numbers but arbitrary elements and I wanted to assign their values to variable names.

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• How to set the bounce address using System.Net.Mail?

  - by Anthony

  I'm trying to implement the Variable envelope return path (VERP) method to manage email addresses (ie when an email I send bounces back I want it to be sent to a specific email address so that I can update my database to avoid sending emails to that email address in the future). According to this article it is possible to specify the email address a bounce email is sent to. How do you do this in .Net? For example say I ([email protected]) want to send an email to you ([email protected]). If [email protected] doesn't exist anymore I want yourserver to send the bounce email to [email protected]). This way when I receive this bounced email I know that [email protected] is not a valid email address anymore and I can update my database accordingly. In this example, the bounce address would be: [email protected] How do you specify it using System.Net.Mail?

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• How to store and access ajax data in javascript without using global variables ?

  - by mike_t2e

  I may be missing something obvious here, but how could I rewrite this code so that it doesn't need the theVariable to be a global variable ? <script language="javascript"> theVariable = ""; function setValue() /* called on page load */ { /* make ajax call to the server here */ theVariable = "a string of json data waiting to be eval()'d"; } function getValue() { alert(theVariable); } </script> <input type="button" onClick="javascript:getValue()" value="Get the value"> In my actual situation, the setValue function makes an ajax call to the server, receives a json string and the data from that is accessed when you mouseover various parts of the page. I end up using several global variables which works fine, but is messy and I'd like to know if there's a better and more elegant way of doing it ?

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• how to use expressons as function parameters in powershell

  - by rmeador

  This is a very simple task in every language I have ever used, but I can't seem to figure it out in PowerShell. An example of what I'm talking about in C: abs(x + y) The expression x + y is evaluated, and the result passed to abs as the parameter... how do I do that in PowerShell? The only way I have figured out so far is to create a temporary variable to store the result of the expression, and pass that. PowerShell seems to have very strange grammar and parsing rules that are constantly catching me by surprise, just like this situation. Does anyone know of documentation or a tutorial that explains the basic underlying theory of the language? I can't believe these are all special cases, there must be some rhyme or reason that no tutorial I have yet read explains. And yes, I've read this question, and all of those tutorials are awful. I've pretty much been relegated to learning from existing code.

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• Checking date against date range in Python

  - by Flowpoke

  I have a date variable: 2011-01-15 and I would like to get a boolean back if said date is within 3 days from TODAY. Im not quite sure how to construct this in Python. Im only dealing with date, not datetime. My working example is a "grace period". A user logs into my site and if the grace period is within 3 days of today, additional scripts, etc. are omitted for that user. I know you can do some fancy/complex things in Python's date module(s) but Im not sure where to look.

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• Using SHIFT_JIS text in PHP

  - by Joe Corkery

  I am building a form that needs to accept characters encoded in SHIFT_JIS and then send those results via email to a recipient. I've tried to simply capture the results from the $_POST variable and then to insert them into a block of text like this: $contents = <<<TEST Name: $NameJp ... TEST but that doesn't appear to work (which doesn't really surprise me). This is my first attempt at dealing with non-ASCII characters in PHP and I am hoping that people might have some suggestions. Perhaps I am missing a simple function to encode the text. Also, are there any other potential pitfalls that I might encounter? Thanks.

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• Python list as *args?

  - by Cap

  I have two Python functions, both of which take variable arguments in their function definitions. To give a simple example: def func1(*args): for arg in args: print arg def func2(*args): return [2 * arg for arg in args] I'd like to compose them -- as in func1(func2(3, 4, 5)) -- but I don't want args in func1 to be ([6, 7, 8],), I want it to be (6, 7, 8), as if it was called as func1(6, 7, 8) rather than func1([6, 7, 8]). Normally, I would just use func1(*func2(3, 4, 5)) or have func1 check to see if args[0] was a list. Unfortunately, I can't use the first solution in this particular instance and to apply the second would require doing such a check in many places (there are a lot of functions in the role of func1). Does anybody have an idea how to do this? I imagine some sort of introspection could be used, but I could be wrong.

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• How do I get python to load .NET .dlls referenced by mixed mode .dlls?

  - by Michael Kelley

  I have a python .pyd that is a mixed mode C++ DLL. The DLL loads fine and loads unmanaged C++ dlls without a problem, but when it tries to load the .NET dlls referenced by the managed C++ dlls it fails with this error message: Unhandled Exception: System.IO.FileNotFoundException: Could not load file or assembly '...' Copying these .NET dlls to the directory that pythod_d.exe is contained in allows the .NET libraries to load successfully, but this is not a good long term solution. Is there an environment variable I have to set or some command line option to python_d.exe that will solve my problem? Note that using IronPython or Python .NET is NOT acceptable.

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• Posting null values via AJAX

  - by nickf

  Using the jQuery $.post function, if you send a null value, it arrives at the server side as "null". Example: Javascript: $.post('test.php', { foo : null }); PHP: var_dump($_POST['foo']); // string(4) "null" I understand why this is so, but was wondering the best way to work around the limitation? Should you: Loop through all the variables in JS before you send them and replace with an empty string? Interpret "null" as null on the server side? Don't send the variable at all? Something else?

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• using subset but old variables still left

  - by user2520852

  I am working with a data set, which is basically daily usage data (let's just say variable X and Y) by different cities (about 150 cities). I have created a subset of data for only specific cities, choosing just 3 of the 150 cities. Then when I do tapply by cities, I get means for 3 cities but also get NA for all other 147 cities that was in the data set. I am using the below coding df<-read.csv(...) df_sub<-subset(df,df$City==1|df$City==3|df$City==19) X_Breakdown<-tapply(X,df_sub$City, mean, na.rm=TRUE) Print(X_Breakdown) City 1 City 2 15 NA City 3 City 4 12 NA City 5 City 6 NA NA Hope you get the idea. I would like to get a dataset that only contains the 3 cities that I'm interested in. It seems that the set of variables is encoded in R, is there a way to fix this? Kindly advise. Thanks

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• Documenting preprocessor defines in Doxygen

  - by Fire Lancer

  Is it possible to document preprocessor defines in Doxygen? I expected to be able to do it just like a variable or function, however the Doxygen output appears to have "lost" the documentation for the define, and does not contain the define its self either. I tried the following /**My Preprocessor Macro.*/ #define TEST_DEFINE(x) (x*x) and /**@def TEST_DEFINE My Preprocessor Macro. */ #define TEST_DEFINE(x) (x*x) I also tried putting them within a group (tried defgroup, addtogroup and ingroup) rather than just at the "file scope" however that had no effect either (although other items in the group were documented as intended). I looked through the various Doxygen options, but couldn't see anything that would enable (or prevent) the documentation of defines.

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• Specify only the second parameter in a javascript function

  - by Ben McCormack

  The spec for the jQuery ajax.error function is: error(XMLHttpRequest, textStatus, errorThrown)Function I'm trying to catch the error and display the textStatus, but I can't figure out how to specify only the textStatus without having to put in a variable name for XMLHttpRequest and errorThrown. My code currently looks like this: $.ajax({ type: "POST", contentType: "application/json; charset=utf-8", url: hbAddressValidation.webServiceUrl, data: this.jsonRequest, dataType: "json", timeout: 5, success: function (msgd) { //... }, error: function (a,textStatus,b) { $("#txtAjaxError").val("There was an error in the AJAX call: " + textStatus); } }); You can see in my code that I'm putting variables a and b as placeholders for the first and last variables in the error function. I know that in my success function, I'm only providing one parameter and it works fine, but in that case data is the first parameter. In the case of error, textStatus is the second parameter, but that's the only one I want to specify. Is this possible?

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• Build Path issue with Java Android project when starting Eclipse

  - by Matt Smith

  I booted up eclipse to start on a project, and without typing in a word I already have several errors. package department.namespace; import android.app.Activity; import android.os.Bundle; public class DepartmentActivity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); } } At package department.namespace, it says: multiple marks at this line and the type java.lang.Object cannot be resolved. It is indirectly referenced from required .class files The import android.os cannot be resolved. Override cannot be resolved as a type The method OnCreate(Bundle) is undefined for the type Activity R. cannot be resolved as a variable. Since this JUST came up when I started Eclipse, how do I fix this?

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• a simple secenerio to implement java script asp.net C#, question rephrased

  - by user287745

  i had asked this question before but got no answer correct. so, this is a simple thing textbox.text='user typing'; button:-store the value to a variable and a database. very simple nothing to it but there should be no post back, that is the page must not load again, try ajax? tried it not working i must a lot of time trying to implement this using java script ajax and read many many post, but for some reason i cannot implement the functionality correctly. please help. thank you

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• XQuery fn:replace not behaving as expected

  - by CoolGravatar

  I have an Excel worksheet in XML format which contains <Cell ss:StyleID="s127"><Data ss:Type="String">A01-Replace</Data></Cell> I want to replace @A01-Replace with a different string. I'm using the XQuery's replace function like so: let $excel := doc("excel.xml") let $test := "another string" return replace($excel, "(A[0-9]+-Replace)", $test) Before calling replace, the variable $excel is valid XML upon output. However, when I output $excel after I call the replace function, all of the XML tags have been stripped, and $excel is a string with the content of the cells as its values. I would like to keep the XML tags there. Any ideas?

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• How to increment a value using a C-Preprocessor in Objective-C?

  - by mystify

  Example: I try to do this: static NSInteger stepNum = 1; #define METHODNAME(i) -(void)step##i #define STEP METHODNAME(stepNum++) @implementation Test STEP { // do stuff... [self nextFrame:@selector(step2) afterDelay:1]; } STEP { // do stuff... [self nextFrame:@selector(step3) afterDelay:1]; } STEP { // do stuff... [self nextFrame:@selector(step4) afterDelay:1]; } // ... When building, Xcode complains that it can't increment stepNum. This seems logical to me, because at this time the code is not "alive" and this pre-processing substitution stuff happens before actually compiling the source code. Is there another way I could have an variable be incremented on every usage of STEP macro, the easy way?

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• converting string to int in C++

  - by xbonez

  I am trying to convert a string I read in from a file to an int value so I can store it in an integer variable. This is what my code looks like: ifstream sin; sin.open("movie_output.txt"); string line; getline(sin,line); myMovie.setYear(atoi(line)); Over here, setYear is a mutator in the Movie class (myMovie is an object of Movie class) that looks like this: void Movie::setYear(unsigned int year) { year_ = year; } When I run the code, I get the following error: error C2664: 'atoi' : cannot convert parameter 1 from 'std::string' to 'const char *' 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

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• how much concurrent http request can erlang handle

  - by user209123

  I am developing a application for benchmarking purposes, for which I require to create large number of http connection in a short time, I created a program in java to test how much threads is java able to create, it turns out in my 2GB single core machine, the limit is variable between 5000 and 6000 with 1 GB of memory given to JVM after which it hits outofmemoryerror with heap limit reached. It is suggested around that erlang will be able to generate much more concurrent processes, I am willing to learn erlang if it is capable of solving the problem , although I am interested in knowing can erlang be able to say generate somewhere around 100000 processes which are essentially http requests waiting for responses, in a matter of few seconds without reaching any limit like memory error etc.,

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• Dynamically create and cast objects at runtime

  - by vaibhav bindroo

  Let's say we have 2 classes A and B public class A{ private int member1; A() { member1 = 10; } public getMember(){ return member1; } } Class B is also on the same lines except that its member variable is named member2 and gets intitialized to say 20 inside the constructor. My Requirement : At runtime , I get a string which contains a className ( could be A or B). I want to dynamically create an object of this class along with invoking the constructor. How can I achieve this . I don't want to use interfaces for common functionality of above classes Morever, later on I set the properties of this raw object using Propery Builder Bean Util class based on a list of columns . Class clazz = Class.forName("className"); Obj obj = clazz.newInstance(); How I can dynamically convert that obj to className object.

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• JS 2 minute countdown then execute a function?

  - by Cyprus106

  I'm not that great at Javascript, for the record! I DO know how to use ajax. I just need a bit of help. I'm having a hard time figuring out how to display a 5 minute countdown, and once the countdown hits zero, to run a function. I need to pass a variable to the function that needs to run. I tried SetInterval but this isn't exactly my strong suit. Does anyone have any suggestions? I can post the code I've got, but I would equate it to a gorilla fumbling in the dark at a typewriter!

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• fread() behaves weird

  - by Cres

  hi, I have a problem in a C program of mine where after I use fread(), the file pointer goes to the end of the file sometimes. I'll try to explain better - the code looks something like: dummy = ftell(fp); fread(&buf, sizeof(unsigned char), 8, fp); dummy = ftell(fp); where fp is a file pointer to an opened file (opened it with "w+", I'm using it as a binary file and I know i'm supposed to have a "b" in there too, but I heard its not really important to add it..), dummy is just an unsigned long variable, and buf is unsigned char[8] now, when debugging, at the ftell before the fread, dummy is 262062 at the ftell after the fread, dummy is 262640 even though I only 'moved' 8 bytes.. does anyone have any idea what can be the cause of this..? thanks for your help :)

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• R: how can I concatenate a list?

  - by John

  I'm trying to produce a single variable which is a concatenation of two chars e.g to go from "p30s4" "p28s4" to "p30s4 p28s4". I've tried cat and paste as shown below. Both return empty variables. What am I doing wrong? > blah = c("p30s4","p28s4") > blah [1] "p30s4" "p28s4" > foo = cat(blah) p30s4 p28s4 > foo NULL > foo = paste(cat(blah)) p30s4 p28s4 > foo character(0)

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