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• Prototype Library use of !! operator

  - by Rajat

  Here is a snippet from Prototype Javascript Library : Browser: (function(){ var ua = navigator.userAgent; var isOpera = Object.prototype.toString.call(window.opera) == '[object Opera]'; return { IE: !!window.attachEvent && !isOpera, Opera: isOpera, WebKit: ua.indexOf('AppleWebKit/') > -1, Gecko: ua.indexOf('Gecko') > -1 && ua.indexOf('KHTML') === -1, MobileSafari: /Apple.*Mobile/.test(ua) } })(), This is all good and i understand the objective of creating a browser object. One thing that caught my eye and I haven't been able to figure out is the use of double not operator !! in the IE property. If you read through the code you will find it at many other places. I dont understand whats the difference between !!window.attachEvent and using just window.attachEvent. Is it just a convention or is there more to it that's not obvious?

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• Redirect output of Python program to /dev/null

  - by STM

  I have a Python executable, written and compiled by somebody else, that I simply need to run once halfway down my own bash script. The program uses a text-based UI, therefore waits for input before proceeding, but the key operations it performs when starting are required in my bash script. A messy (and strange) procedure I know, but unfortunately I haven't got any other options. I've gotten around forcefully closing the program with a kill signal, but the program's TUI insists on outputting to wherever it's run. I've tried redirecting both stdout and stderr to /dev/null and running the program in the background by suffixing an ampersand, but simply can't get it to play ball. I believe the cause is the program spawns other processes, and the output redirection of the parent process doesn't affect them. Is there any trick I can utilise to redirect all output from child processes too?

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• Intent Bundle returns Null every time?

  - by Max

  I have some extras sent to a new intent. There it grabs the bundle and tests if it is null. Every single time it is null even though I am able to get the values passed and use them. Can anyone see what is wrong with the if statement? Intent i = getIntent(); Bundle b = i.getExtras(); int picked = b.getInt("PICK"); int correct = b.getInt("CORR"); type = b.getString("RAND"); if(b == null || !b.containsKey("WELL")) { Log.v("BUNDLE", "bun is null"); } else { Log.v("BUNDLE", "Got bun well"); } EDIT: Heres where the bundle is created. Intent intent = new Intent(this, app.pack.son.class); Bundle b = new Bundle(); b.putInt("PICK", pick); b.putInt("CORR", corr); b.putString("RAND", "yes"); intent.putExtras(b); startActivity(intent);

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• Avoiding null point exception in el in JSF

  - by Buddhika Ariyaratne

  I am developing a JSF application with JPA(EclipseLink 2.0) and Primefaces. I want to know is there any way to avoid null point exception when el calls a property of a null object. I have described the situation. I have Bill class. There may be no or more BillItem objects with a Bill objects. Each BillItem object have Objects like Make, Country, Manufacturer, etc objects. I am displaying several properties of a bill within a single JSF file like this. "#{billControlled.bill.billItem.modal.name}" But if a bill is not selected, or when there are no bill items for a selected bill, the properties accessing in the el are null. I can avoid this by creating new objects for every bill, for example, new make for a new bill item, etc or by creating new properties in the controller itself for all the properties. But that is a very long way and feel like rudimentory. Is there any good practice to avoid this null point exception in el in JSF?

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• std::string == operator not working

  - by Paul

  Hello, I've been using std::string's == operator for years on windows and linux. Now I am compiling one of my libraries on linux, it uses == heavily. On linux the following function fails, because the == returns false even when the strings are equal (case sensitive wise equal) const Data* DataBase::getDataByName( const std::string& name ) const { for ( unsigned int i = 0 ; i < m_dataList.getNum() ; i++ ) { if ( m_dataList.get(i)->getName() == name ) { return m_dataList.get(i); } } return NULL; } The getName() method is declared as follows virtual const std::string& getName() const; I am building with gcc 4.4.1 and libstdc++44-4.4.1. Any ideas? it looks perfectly valid to me. Paul

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• MySQL DDL error creating tables

  - by Alexandstein

  I am attempting to create tables for a MySQL database, but I am having some syntactical issues. It would seem that syntax checking is behaving differently between tables for some reason. While I've gotten all the other tables to go through, the table, 'stock' doesn't seem to be working, despite seeming to use the same syntax patterns. CREATE TABLE users ( user_id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT, username VARCHAR(30) NOT NULL, password CHAR(41) NOT NULL, date_joined DATETIME NOT NULL, funds DOUBLE UNSIGNED NOT NULL, PRIMARY KEY(user_id), UNIQUE KEY(username) ); CREATE TABLE owned_stocks ( id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT, user_id SMALLINT UNSIGNED NOT NULL, paid_price DOUBLE UNSIGNED NOT NULL, quantity MEDIUMINT UNSIGNED NOT NULL, purchase_date DATETIME NOT NULL, PRIMARY KEY(id) ); CREATE TABLE tracking_stocks ( ticker VARCHAR(5) NOT NULL, user_id SMALLINT UNSIGNED NOT NULL, PRIMARY KEY(ticker) ); CREATE TABLE stocks ( ticker VARCHAR(5) NOT NULL, last DOUBLE UNSIGNED NOT NULL, high DOUBLE UNSIGNED NOT NULL, low DOUBLE UNSIGNED NOT NULL, company_name VARCHAR(30) NOT NULL, last_updated INT UNSIGNED NOT NULL, change DOUBLE NOT NULL, percent_change DOUBLE NOT NULL, PRIMARY KEY(ticker) ); Am I just missing a really obvious syntactical issue? ERROR: #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'change DOUBLE NOT NULL, percent_change DOUBLE NOT NULL, last DOUBLE' at line 4

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• Parallel Assignment operator in Ruby

  - by Bragaadeesh

  Hi, I was going through an example from Programming in Ruby book. This is that example def fib_up_to(max) i1, i2 = 1, 1 # parallel assignment (i1 = 1 and i2 = 1) while i1 <= max yield i1 i1, i2 = i2, i1+i2 end end fib_up_to(100) {|f| print f, " " } The above program simply prints the fibonacci numbers upto 100. Thats fine. My question here is when i replace the parallel assignment with something like this, i1 = i2 i2 = i1+i2 I am not getting the desired output. My question here is, is it advisable to use parallel assignments? (I come from Java background and it feels really wierd to see this type of assignment) One more doubt is : Is parallel assignment an operator?? Thanks

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• How can I declare and initialize an array of pointers to a structure in C?

  - by worlds-apart89

  I have a small assignment in C. I am trying to create an array of pointers to a structure. My question is how can I initialize each pointer to NULL? Also, after I allocate memory for a member of the array, I can not assign values to the structure to which the array element points. #include <stdio.h> #include <stdlib.h> typedef struct list_node list_node_t; struct list_node { char *key; int value; list_node_t *next; }; int main() { list_node_t *ptr = (list_node_t*) malloc(sizeof(list_node_t)); ptr->key = "Hello There"; ptr->value = 1; ptr->next = NULL; // Above works fine // Below is erroneous list_node_t **array[10] = {NULL}; *array[0] = (list_node_t*) malloc(sizeof(list_node_t)); array[0]->key = "Hello world!"; //request for member ‘key’ in something not a structure or union array[0]->value = 22; //request for member ‘value’ in something not a structure or union array[0]->next = NULL; //request for member ‘next’ in something not a structure or union // Do something with the data at hand // Deallocate memory using function free return 0; }

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• The data types text and nvarchar are incompatible in the equal to operator

  - by metro

  Hi there. this is my code ProductController.cs public ActionResult Details(string id) { product productx = productDB.products.Single(pr => pr.Product1 == id); return View(productx); } Details.aspx <td> <%-- : Html.ActionLink("Edit", "Edit", new { id=item.Id }) % --> <%: Html.ActionLink("Details", "Details", new { id = item.Product1 })%> </td> this is what im using to list some products from a sql database, each product have a link to a Details page to show more informations about it what Im trying is to only put the product label in that link to let it show something like www.mysite.com\products\battery (not the id) I've imagined this should work, but it throw an The data types text and nvarchar are incompatible in the equal to operator. error and neither (pr => pr.Product1.Equals(id)); works the error is clear and Im asking how should I do to make it work this way ? thanks

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• What's the purpose of having a separate "operator new[]" ?

  - by sharptooth

  Looks like operator new and operator new[] have exactly the same signature: void* operator new( size_t size ); void* operator new[]( size_t size ); and do exactly the same: either return a pointer to a big enough block of raw (not initialized in any way) memory or throw an exception. Also operator new is called internally when I create an object with new and operator new[] - when I create an array of objects with new[]. Still the above two special functions are called by C++ internally in exactly the same manner and I don't se how the two calls can have different meanings. What's the purpose of having two different functions with exactly the same signatures and exactly the same behavior?

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• C++ return a "NULL" object if search result not found

  - by aduric

  I'm pretty new to C++ so I tend to design with a lot of Java-isms while I'm learning. Anyway, in Java, if I had class with a 'search' method that would return an object T from a Collection< T that matched a specific parameter, I would return that object and if the object was not found in the collection, I would return a NULL. Then in my calling function I would just check if(T != NULL) { ... } In C++, I'm finding out that I can't return a NULL if the object doesn't exist. I just want to return an 'indicator' of type T that notifies the calling function that no object has been found. I don't want to throw an exception because it's not really an exceptional circumstance. class Node { .... Attr& getAttribute(const string& attribute_name) const { //search collection //if found at i return attributes[i]; //if not found return NULL; } private: vector<Attr> attributes; }

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• regarding like query operator

  - by stackoverflowuser

  Hi For the below data (well..there are many more nodes in the team foundation server table which i need to refer to..below is just a sample) Nodes ------------------------ \node1\node2\node3\ \node1\node2\node5\ \node1\node2\node3\node4 I was wondering if i can apply something like (below query does not give the required results) select * from table_a where nodes like '\node1\node2\%\' to get the below data \node1\node2\node3\ \node1\node2\node5\ and something like (below does not give the required results) select * from table_a where nodes like '\node1\node2\%\%\' to get \node1\node2\node3\ \node1\node2\node5\ \node1\node2\node3\node4 Can the above be done with like operator? Pls. suggest. Thanks

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• Does replacing statements by expressions using the C++ comma operator could allow more compiler opti

  - by Gabriel Cuvillier

  The C++ comma operator is used to chain individual expressions, yielding the value of the last executed expression as the result. For example the skeleton code (6 statements, 6 expressions): step1; step2; if (condition) step3; return step4; else return step5; May be rewritten to: (1 statement, 6 expressions) return step1, step2, condition? step3, step4 : step5; I noticed that it is not possible to perform step-by-step debugging of such code, as the expression chain seems to be executed as a whole. Does it means that the compiler is able to perform special optimizations which are not possible with the traditional statement approach (specially if the steps are const or inline)? Note: I'm not talking about the coding style merit of that way of expressing sequence of expressions! Just about the possible optimisations allowed by replacing statements by expressions.

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• OS X Automator empty, blank or null value.

  - by Brian

  I have some data files mostly excel, word and pdf files most of the files have no extension on them. So they are missing the .doc .xls. This data needs to be used in a Windows environment now. I have created automator apps for each of the file types I want to add the ext onto. The problem is it also adds the extension to files that already have an extension. So data.xls becomes data.xls.xls I would like to figure a way to only add the extenion to the files without extension. How do I tell the finder filter that i only want it to return files without extensions. I see how to add a line to filter by extension but I don't know how to let it know I want only blank or null or files without any extensions. Thanks

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• Overriding rubies spaceship operator <=>

  - by ericsteen1

  I am trying to override rubies <= (spaceship) operator to sort apples and oranges so that apples come first sorted by weight, and oranges second, sorted by sweetness. Like so: module Fruity attr_accessor :weight, :sweetness def <=>(other) # use Array#<=> to compare the attributes [self.weight, self.sweetness] <=> [other.weight, other.sweetness] end include Comparable end class Apple include Fruity def initialize(w) self.weight = w end end class Orange include Fruity def initialize(s) self.sweetness = s end end fruits = [Apple.new(2),Orange.new(4),Apple.new(6),Orange.new(9),Apple.new(1),Orange.new(22)] p fruits #should work? p fruits.sort But this does not work, can someone tell what I am doing wrong here, or a better way to do this?

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• USing Min/Max with conditional operator

  - by user638501

  Hello All, I am trying to run a query to find max and min values, and then use a conditional operator. however when I try to run the following query, it gives me error - "misuse of aggregate: min()". My query is: SELECT a.prim_id, min(b.new_len*36) as min_new_len, max(b.new_len*36) as max_new_len FROM tb_first a, tb_second b WHERE a.sec_id = b.sec_id AND min_new_len > 1900 AND max_new_len < 75000 GROUP BY a.prim_id ORDER BY avg(b.new_len*36); Any suggestions ?

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• .save puts NULL in id field in Rails

  - by mathee

  Here's the model file: class ProfileTag < ActiveRecord::Base def self.create_or_update(options = {}) id = options.delete(:id) record = find_by_id(id) || new record.id = id record.attributes = options puts "record.profile_id is" puts record.profile_id record.save! record end end This gives me the correct print out in my log. But it also says that there's a call to UPDATE that sets profile_id to NULL. Here's some of the output in the log file: Processing ProfilesController#update (for 127.0.0.1 at 2010-05-28 18:20:54) [PUT] Parameter: {"commit"=>"Save", ...} ?[4;36;1mProfileTag Create (0.0ms)?[0m ?[0;1mINSERT INTO `profile_tags` (`reputation_value`, `updated_at`, `tag_id`, `id`, `profile_id`, `created_at`) VALUES(0, '2010-05-29 01:20:54', 1, NULL, 4, '2010-05-29 01:20:54')?[0m ?[4;35;1mSQL (2.0ms)?[0m ?[0mCOMMIT?[0m ?[4;36;1mSQL (0.0ms)?[0m ?[0;1mBEGIN?[0m ?[4;35;1mSQL (0.0ms)?[0m ?[0mCOMMIT?[0m ?[4;36;1mProfileTag Load (0.0ms)?[0m ?[0;1mSELECT * FROM `profile_tags` WHERE (`profile_tags`.profile_id = 4) ?[0m ?[4;35;1mSQL (1.0ms)?[0m ?[0mBEGIN?[0m ?[4;36;1mProfileTag Update (0.0ms)?[0m ?[0;1mUPDATE `profile_tags` SET profile_id = NULL WHERE (profile_id = 4 AND id IN (35)) ?[0m I'm not sure I understand why the INSERT puts the value into profile_id properly, but then it sets it to NULL on an UPDATE. If you need more specifics, please let me know. I'm thinking that the save functionality does many things other than INSERTs into the database, but I don't know what I need to specify so that it will properly set profile_id.

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• Boolean Not operator in VBScript

  - by Lumi

  Consider the following two conditionals (involving bitwise comparisons) in VBScript: If 1 And 3 Then WScript.Echo "yes" Else WScript.Echo "no" If Not(1 And 3) Then WScript.Echo "yes" Else WScript.Echo "no" Prints first yes, then no, right? cscript not.vbs Wrong! It prints yes twice! Wait a second, the Not operator is supposed to perform logical negation on an expression. The logical negation of true is false, as far as I know. Must I conclude that it doesn't live up to that promise? How and why and what is going on here? What is the rationale, if any?

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• Why does std::map operator[] create an object if the key doesn't exist?

  - by n1ck

  Hi, I'm pretty sure I already saw this question somewhere (comp.lang.c++? Google doesn't seem to find it there either) but a quick search here doesn't seem to find it so here it is: Why does the std::map operator[] create an object if the key doesn't exist? I don't know but for me this seems counter-intuitive if you compare to most other operator[] (like std::vector) where if you use it you must be sure that the index exists. I'm wondering what's the rationale for implementing this behavior in std::map. Like I said wouldn't it be more intuitive to act more like an index in a vector and crash (well undefined behavior I guess) when accessed with an invalid key? Refining my question after seeing the answers: Ok so far I got a lot of answers saying basically it's cheap so why not or things similar. I totally agree with that but why not use a dedicated function for that (I think one of the comment said that in java there is no operator[] and the function is called put)? My point is why doesn't map operator[] work like a vector? If I use operator[] on an out of range index on a vector I wouldn't like it to insert an element even if it was cheap because that probably mean an error in my code. My point is why isn't it the same thing with map. I mean, for me, using operator[] on a map would mean: i know this key already exist (for whatever reason, i just inserted it, I have redundancy somewhere, whatever). I think it would be more intuitive that way. That said what are the advantage of doing the current behavior with operator[] (and only for that, I agree that a function with the current behavior should be there, just not operator[])? Maybe it give clearer code that way? I don't know. Another answer was that it already existed that way so why not keep it but then, probably when they (the ones before stl) choose to implement it that way they found it provided an advantage or something? So my question is basically: why choose to implement it that way, meaning a somewhat lack of consistency with other operator[]. What benefit do it give? Thanks

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• Analyzing Python Code: Modulus Operator

  - by Bhubhu Hbuhdbus

  I was looking at some code in Python (I know nothing about Python) and I came across this portion: def do_req(body): global host, req data = "" s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((host, 80)) s.sendall(req % (len(body), body)) tmpdata = s.recv(8192) while len(tmpdata) > 0: data += tmpdata tmpdata = s.recv(8192) s.close() return data This is then called later on with body of huge size, as in over 500,000 bytes. This is sent to an Apache server that has the max request size on the default 8190 bytes. My question is what is happening at the "s.sendall()" part? Obviously the entire body cannot be sent at once and I'm guessing it is reduced by way of the modulus operator. I don't know how it works in Python, though. Can anyone explain? Thanks.

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• Overriding Ruby's spaceship operator <=>

  - by ericsteen1

  I am trying to override Ruby's <= (spaceship) operator to sort apples and oranges so that apples come first sorted by weight, and oranges second, sorted by sweetness. Like so: module Fruity attr_accessor :weight, :sweetness def <=>(other) # use Array#<=> to compare the attributes [self.weight, self.sweetness] <=> [other.weight, other.sweetness] end include Comparable end class Apple include Fruity def initialize(w) self.weight = w end end class Orange include Fruity def initialize(s) self.sweetness = s end end fruits = [Apple.new(2),Orange.new(4),Apple.new(6),Orange.new(9),Apple.new(1),Orange.new(22)] p fruits #should work? p fruits.sort But this does not work, can someone tell what I am doing wrong here, or a better way to do this?

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• Nhibernate:null index column for collection Error

  - by Quintin Par

  I am working a subsonic to NH migration(I can’t change the schema) and while creating the mapping I came across this error null index column for collection: Company.Core.CompanyUser.Addresses My mapping from the User side is mapping.HasMany(x => x.Addresses).AsList().KeyColumn("user_id").Cascade.All().Inverse(); xml <list cascade="all" inverse="true" name="Addresses"> <key> <column name="user_id" /> </key> <index /> <one-to-many class="Company.Core.CompanyAddress, Company.Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" /> </list> On the Address side it is mapping.CompositeId().KeyReference(x => x.User, "user_id").KeyProperty(x => x.Type); xml <composite-id mapped="false" unsaved-value="undefined"> <key-property name="Type" type="System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <column name="Type" /> </key-property> <key-many-to-one name="User" class="Company.Core.CompanyUser, Company.Core, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"> <column name="user_id" /> </key-many-to-one> </composite-id> When I try to load this collection as user.Addresses I get the index null exception. How do I fix this error?

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• Checkboxes in ADF are initially null, where I want them to be 0

  - by Mark Tielemans

  I am using ADF in JDeveloper and don´t have any experience with either of the two. Now I´ve run into quite some trouble yet, but for this particular thing I decided to consult the wisom of stackoverflow. The thing is, I have an edit form for an object that contains 3 checkboxes. The checked values are set to 1, unchecked to 0. In my database, the values are NOT NULL, and I want to keep it that way. The thing is, in the edit form, if the user submits the form leaving any boxes unchecked, it will result in an error, because the unchecked box values apparently remain null. Only after checking and then unchecking the boxes again, their values will be '0' rather than null. I've tried some things, including making the attributes mandatory in the domain BCD, but that just gives a bit more neat error message.. Any help would be greatly appreciated!! EDIT I made a little progress thanks to the guide provided by Joe, but still run into problems. I changed the values that should be checkboxes in my model, making them BOOLEANs where the table columns are NUMBERs (All are also mandatory and have a default value of 0). This automatically changed the corresponding View Object too. In the Application module, this now works great. It shows checkboxes, a checked one will return 1, an untouched one will return 0. However, I deleted the old form, and inserted a new one using the corresponding Data Control. I gave these values the checkbox type. I still had to edit the bindings (which I think reflects the problem, as this is not the case with, say, a model-level defined LOV) and gave them 1 for checked and 0 for unchecked. However, now apart from the original problem still occurring, also the checkboxes cannot be unchecked after checking, and return 0 when checked (and null when left untouched). Even though this has created new problems, it works correctly in my AM. Does someone know what I'm doing wrong in my Swing form?

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• typeof === "undefined" vs. != null

  - by Thor Thurn

  I often see JavaScript code which checks for undefined parameters etc. this way: if (typeof input !== "undefined") { // do stuff } This seems kind of wasteful, since it involves both a type lookup and a string comparison, not to mention its verbosity. It's needed because 'undefined' could be renamed, though. My question is: How is that code any better than this approach: if (input != null) { // do stuff } As far as I know, you can't redefine null, so it's not going to break unexpectedly. And, because of the type-coercion of the != operator, this checks for both undefined and null... which is often exactly what you want (e.g. for optional function parameters). Yet this form does not seem widespread, and it even causes JSLint to yell at you for using the evil != operator. Why is this considered bad style?

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• C++ vector<T>::iterator operator +

  - by Tom

  Hi, Im holding an iterator that points to an element of a vector, and I would like to compare it to the next element of the vector. Here is what I have Class Point{ public: float x,y; } //Somewhere in my code I do this vector<Point> points = line.getPoints(); foo (points.begin(),points.end()); where foo is: void foo (Vector<Point>::iterator begin,Vector<Point>::iterator end) { std::Vector<Point>::iterator current = begin; for(;current!=end-1;++current) { std::Vector<Point>::iterator next = current + 1; //Compare between current and next. } } I thought that this would work, but current + 1 is not giving me the next element of the vector. I though operator+ was the way to go, but doesnt seem so. Is there a workaround on this? THanks

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