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• How to pass common arguments to Perl modules

  - by Leonard

  I'm not thrilled with the argument-passing architecture I'm evolving for the (many) Perl scripts that have been developed for some scripts that call various Hadoop MapReduce jobs. There are currently 8 scripts (of the form run_something.pl) that are run from cron. (And more on the way ... we expect anywhere from 1 to 3 more for every function we add to hadoop.) Each of these have about 6 identical command-line parameters, and a couple command line parameters that are similar, all specified with Euclid. The implementations are in a dozen .pm modules. Some of which are common, and others of which are unique.... Currently I'm passing the args globally to each module ... Inside run_something.pl I have: set_common_args (%ARGV); set_something_args (%ARGV); And inside Something.pm I have sub set_something_args { (%MYARGS) =@_; } So then I can do if ( $MYARGS{'--needs_more_beer'} ) { $beer++; } I'm seeing that I'm probably going to have additional "common" files that I'll want to pass args to, so I'll have three or four set_xxx_args calls at the top of each run_something.pl, and it just doesn't seem too elegant. On the other hand, it beats passing the whole stupid argument array down the call chain, and choosing and passing individual elements down the call chain is (a) too much work (b) error-prone (c) doesn't buy much. In lots of ways what I'm doing is just object-oriented design without the object-oriented language trappings, and it looks uglier without said trappings, but nonetheless ... Anyone have thoughts or ideas?

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• Writing functions of tuples conveniently in Scala

  - by Alexey Romanov

  Quite a few functions on Map take a function on a key-value tuple as the argument. E.g. def foreach(f: ((A, B)) ? Unit): Unit. So I looked for a short way to write an argument to foreach: > val map = Map(1 -> 2, 3 -> 4) map: scala.collection.immutable.Map[Int,Int] = Map(1 -> 2, 3 -> 4) > map.foreach((k, v) => println(k)) error: wrong number of parameters; expected = 1 map.foreach((k, v) => println(k)) ^ > map.foreach({(k, v) => println(k)}) error: wrong number of parameters; expected = 1 map.foreach({(k, v) => println(k)}) ^ > map.foreach(case (k, v) => println(k)) error: illegal start of simple expression map.foreach(case (k, v) => println(k)) ^ I can do > map.foreach(_ match {case (k, v) => println(k)}) 1 3 Any better alternatives?

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• Passing objects across Appdomains

  - by MUSTAQ

  My issue is similar to the one posted in "http://stackoverflow.com/questions/981773/moving-objects-across-appdomains-in-net". In one of my application, I am creating a separate appdomain. I need to create an instance of a class (Note: this class is derived by MarshalByRefObject) in my parent domain and invoke a MethodA in that instance. This instance is created using "CreateInstanceAndUnwrap". The problem is that this MethodA takes objects of type class as an argument. These objects are not created in the MethodB where i created the appdomain. It was passed as an argument to the MethodB where i create the appdomain. So is it necessary to create a new instance of these objects using "CreateInstanceAndUnwrap" before passing it to the created domain. Not doing this gives me an error in the created domain mentioning that "MyClass object has no attribute foo" during some invocation. Please let me know how to pass the objects across appdomains and execute the method. My statements might be confusing, please let me know for any specific details required.

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• Setting Up a Wordpress Function in theme's function.php File

  - by user1609391

  I am trying to create the below function in my theme's function.php file and call it from my taxonomy.php file via query_brands_geo('dealers', 'publish', '1', $taxtype, $geo, $brands); all variables are set in taxonomy.php. The below query works perfect if I put it directly in my taxonomy.php file. What am I missing to make this work as a function? As a function I get this error statement for argument repeated for 2-6: Warning: Missing argument 2 for query_brands_geo() function query_brands_geo($posttype, $poststatus, $paidvalue, $taxtype, $geo, $brands) { /* Custom Query for a brand/geo combination to display dealers with a certain brand and geography */ //Query only for brands/geography combo and paid dealers $wp_query = new WP_Query(); $args = array( 'post_type' => '$posttype', 'post_status' => array($poststatus), 'orderby' => 'rand', 'posts_per_page' => 30, 'meta_query' => array( array( 'key' => 'wpcf-paid', 'value' => array($paidvalue), 'compare' => 'IN', ) ), 'tax_query' => array( 'relation' => 'AND', array( 'taxonomy' => $taxtype, 'field' => 'slug', 'terms' => $geo ), array( 'taxonomy' => 'brands', 'field' => 'slug', 'terms' => $brands ) ) ); $wp_query->query($args); } add_action( 'after_setup_theme', 'query_brands_geo' );

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• How to specify multiple values in where with AR query interface in rails3

  - by wkhatch

  Per section 2.2 of rails guide on Active Record query interface here: which seems to indicate that I can pass a string specifying the condition(s), then an array of values that should be substituted at some point while the arel is being built. So I've got a statement that generates my conditions string, which can be a varying number of attributes chained together with either AND or OR between them, and I pass in an array as the second arg to the where method, and I get: ActiveRecord::PreparedStatementInvalid: wrong number of bind variables (1 for 5) which leads me to believe I'm doing this incorrectly. However, I'm not finding anything on how to do it correctly. To restate the problem another way, I need to pass in a string to the where method such as "table.attribute = ? AND table.attribute1 = ? OR table.attribute1 = ?" with an unknown number of these conditions anded or ored together, and then pass something, what I thought would be an array as the second argument that would be used to substitute the values in the first argument conditions string. Is this the correct approach, or, I'm just missing some other huge concept somewhere and I'm coming at this all wrong? I'd think that somehow, this has to be possible, short of just generating a raw sql string.

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• How to pass a Lambda Expression as method parameter with EF

  - by Registered User

  How do I pass an EF expression as a method argument? To illustrate my question I have created a pseudo code example: The first example is my method today. The example utilizes EF and a Fancy Retry Logic. What I need to do is to encapsulate the Fancy Retry Logic so that it becomes more generic and does not duplicate. In the second example is how I want it to be, with a helper method that accepts the EF expression as an argument. This would be a trivial thing to do with SQL, but I want to do it with EF so that I can benefit from the strongly typed objects. First Example: public static User GetUser(String userEmail) { using (MyEntities dataModel = new MyEntities ()) { var query = FancyRetryLogic(() => { (dataModel.Users.FirstOrDefault<User>(x => x.UserEmail == userEmail))); }); return query; } } Second Example: T RetryHelper<T>(Expression<Func<T, TValue>> expression) { using (MyEntities dataModel = new (MyEntities ()) { var query = FancyRetryLogic(() => { return dataModel.expression }); } } public User GetUser(String userEmail) { return RetryHelper<User>(<User>.FirstOrDefault<User>(x => x.UserEmail == userEmail)) }

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• DBD::CSV: Problem with userdefined functions

  - by sid_com

  From the SQL::Statement::Functions documentation: Creating User-Defined Functions ... More complex functions can make use of a number of arguments always passed to functions automatically. Functions always receive these values in @_: sub FOO { my( $self, $sth, $rowhash, @params ); } #!/usr/bin/env perl use 5.012; use warnings; use strict; use DBI; my $dbh = DBI->connect( "DBI:CSV:", undef, undef, { RaiseError => 1, } ); my $table = 'wages'; my $array_ref = [ [ 'id', 'number' ], [ 0, 6900 ], [ 1, 3200 ], [ 2, 1800 ], ]; $dbh->do( "CREATE TEMP TABLE $table AS import( ? )", {}, $array_ref ); sub routine { my $self = shift; my $sth = shift; my $rowhash = shift; # return $_[0] / 30; }; $dbh->do( "CREATE FUNCTION routine" ); my $sth = $dbh->prepare( "SELECT id, routine( number ) AS result FROM $table" ); $sth->execute(); $sth->dump_results(); When I try this I get an error-message: DBD::CSV::st execute failed: Use of uninitialized value $_[0] in division (/) at ./so.pl line 27. [for Statement "SELECT id, routine( number ) AS result FROM "wages""] at ./so.pl line 34. When I comment out the third argument I works as expected ( because it looks as if the third argument is missing ): #!/usr/bin/env perl ... sub routine { my $self = shift; my $sth = shift; #my $rowhash = shift; return $_[0] / 30; }; ... 0, 230 1, 106.667 2, 60 3 rows Is this a bug?

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• How can I introduce a regex action to match the first element in a Catalyst URI ?

  - by RET

  Background: I'm using a CRUD framework in Catalyst that auto-generates forms and lists for all tables in a given database. For example: /admin/list/person or /admin/add/person or /admin/edit/person/3 all dynamically generate pages or forms as appropriate for the table 'person'. (In other words, Admin.pm has actions edit, list, add, delete and so on that expect a table argument and possibly a row-identifying argument.) Question: In the particular application I'm building, the database will be used by multiple customers, so I want to introduce a URI scheme where the first element is the customer's identifier, followed by the administrative action/table etc: /cust1/admin/list/person /cust2/admin/add/person /cust2/admin/edit/person/3 This is for "branding" purposes, and also to ensure that bookmarks or URLs passed from one user to another do the expected thing. But I'm having a lot of trouble getting this to work. I would prefer not to have to modify the subs in the existing framework, so I've been trying variations on the following: sub customer : Regex('^(\w+)/(admin)$') { my ($self, $c, @args) = @_; #validation of captured arg snipped.. my $path = join('/', 'admin', @args); $c->request->path($path); $c->dispatcher->prepare_action($c); $c->forward($c->action, $c->req->args); } But it just will not behave. I've used regex matching actions many times, but putting one in the very first 'barrel' of a URI seems unusually traumatic. Any suggestions gratefully received.

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• How do I define a monadic function to work on a list in J?

  - by Gregory Higley

  Let's say I have the following J expression: # 3 ((|=0:)#]) 1+i.1000 This counts the number of numbers between 1 and 1000 that are evenly divisible by 3. (Now, before anyone points out that there's an easier way to do this, this question is about the syntax of J, and not mathematics.) Let's say I define a monadic function for this, as follows: f =: monad define # y ((|=0:)#]) 1+i.1000 ) This works great with a single argument, e.g., f 4 250 If I pass a list in, I get a length error: f 1 2 3 |length error: f Now, I completely understand why I get the length error. When you substitute the list 1 2 3 for the y argument of the monad, you get: # 1 2 3 ((|=0:)#]) 1+i.1000 If you know anything about J, it's pretty clear why the length error is occurring. So, I don't need an explanation of that. I want to define the function such that when I pass a list, it returns a list, e.g., f 1 2 3 1000 500 333 How can I either (a) redefine this function to take a list and return a list or (b) get the function to work on a list as-is without being redefined, perhaps using some adverb or other technique?

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• Trouble swapping values as keys in generic java BST class

  - by user1729869

  I was given a generic binary search tree class with the following declaration: public class BST<K extends Comparable<K>, V> I was asked to write a method that reverses the BST such that the values become the keys and keys become values. When I call the following method (defined in the class given) reverseDict.put(originalDict.get(key), key); I get the following two error messages from Netbeans: Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - Erroneous sym type: BST.put And also: no suitable method found for put(V,K) method BST.put(BST<K,V>.Node,K,V) is not applicable (actual and formal argument lists differ in length) method BST.put(K,V) is not applicable (actual argument V cannot be converted to K by method invocation conversion) where V,K are type-variables: V extends Object declared in method <K,V>reverseBST(BST<K,V>) K extends Comparable<K> declared in method <K,V>reverseBST(BST<K,V>) From what the error messages are telling me, since my values do not extend Comparable I am unable to use them as keys. If I am right, how can I get around that without changing the class given (maybe a cast)?

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• casting char[][] to char** causes segfault?

  - by Earlz

  Ok my C is a bit rusty but I figured I'd make my next(small) project in C so I could polish back up on it and less than 20 lines in I already have a seg fault. This is my complete code: #define ROWS 4 #define COLS 4 char main_map[ROWS][COLS+1]={ "a.bb", "a.c.", "adc.", ".dc."}; void print_map(char** map){ int i; for(i=0;i<ROWS;i++){ puts(map[i]); //segfault here } } int main(){ print_map(main_map); //if I comment out this line it will work. puts(main_map[3]); return 0; } I am completely confused as to how this is causing a segfault. What is happening when casting from [][] to **!? That is the only warning I get. rushhour.c:23:3: warning: passing argument 1 of ‘print_map’ from incompatible pointer type rushhour.c:13:7: note: expected ‘char **’ but argument is of type ‘char (*)[5]’ Are [][] and ** really not compatible pointer types? They seem like they are just syntax to me.

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• Error in django using Apache & mod_wsgi

  - by Ignacio

  Hey, I've been doing some changes to my django develpment env, as some of you suggested. So far I've managed to configure and run it successfully with postgres. Now I'm trying to run the app using apache2 and mod_wsgi, but I ran into this little problem after I followed the guidelines from the django docs. When I access localhost/myapp/tasks this error raises: Request Method: GET Request URL: http://localhost/myapp/tasks/ Exception Type: TemplateSyntaxError Exception Value: Caught an exception while rendering: argument 1 must be a string or unicode object Original Traceback (most recent call last): File "/usr/local/lib/python2.6/dist-packages/django/template/debug.py", line 71, in render_node result = node.render(context) File "/usr/local/lib/python2.6/dist-packages/django/template/defaulttags.py", line 126, in render len_values = len(values) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 81, in __len__ self._result_cache = list(self.iterator()) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 238, in iterator for row in self.query.results_iter(): File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py", line 287, in results_iter for rows in self.execute_sql(MULTI): File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py", line 2369, in execute_sql cursor.execute(sql, params) File "/usr/local/lib/python2.6/dist-packages/django/db/backends/util.py", line 19, in execute return self.cursor.execute(sql, params) TypeError: argument 1 must be a string or unicode object ... ... ... And then it highlights a {% for t in tasks %} template tag, like the source of the problem is there, but it worked fine on the built-in server. The view associated with that page is really simple, just fetch all Task objects. And the template just displays them on a table. Also, some pages get rendered ok. Don't want to fill this Question with code, so if you need some more info I'd be glad to provide it. Thanks

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• database design - empty fields

  - by imanc

  Hey, I am currently debating an issue with a guy on my dev team. He believes that empty fields are bad news. For instance, if we have a customer details table that stores data for customers from different countries, and each country has a slightly different address configuration - plus 1-2 extra fields, e.g. French customer details may also store details for entry code, and floor/level plus title fields (madamme, etc.). South Africa would have a security number. And so on. Given that we're talking about minor variances my idea is to put all of the fields into the table and use what is needed on each form. My colleague believes we should have a separate table with extra data. E.g. customer_info_fr. But this seams to totally defeat the purpose of a combined table in the first place. His argument is that empty fields / columns is bad - but I'm struggling to find justification in terms of database design principles for or against this argument and preferred solutions. Another option is a separate mini EAV table that stores extra data with parent_id, key, val fields. Or to serialise extra data into an extra_data column in the main customer_data table. I think I am confused because what I'm discussing is not covered by 3NF which is what I would typically use as a reference for how to structure data. So my question specifically: - if you have slight variances in data for each record (1-2 different fields for instance) what is the best way to proceed?

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• Using external SOAP service in Workflow service

  - by whirlwin

  I am using the .NET 4 framework and have made a WCF Workflow Service Application. I want to use a SOAP web service (.NET 3.5) I have running in another instance of VS. The only method that is exposed is the following: [WebMethod] public string Reverse(string input) { char[] chars = input.ToCharArray(); Array.Reverse(chars); return new string(chars); } I have used the following steps to add the service in my Workflow: Add Service Reference Provided the WSDL (the operation shows in the Operations box as expected) Clicked OK Build the solution to ensure that the service shows in my toolbox Drag the service from the toolbox into the workflow However, when I look at the properties of the service in the workflow, there is no way to specify the input argument or where to store the result of the invocation of the service. I only have the option of specifying some obscure parameters such as Body:InArgument<ReverseRequestBody and outBody:OutArgument<ReverseResponseBody (none of which are strings). Here is a screenshot depicting the properties of the service in the workflow: My question is therefore: Is it possible at all to use the SOAP service by specifying a string as the input argument (like it is meant to be used), and also assign the result to a workflow variable?

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• Increasing understanding of validating a string with PHP string functions

  - by user1554264

  I've just started attempts to validate data in PHP and I'm trying to understand this concept better. I was expecting the string passed as an argument to the $data parameter for the test_input() function to be formatted by the following PHP functions. trim() to remove white space from the end of the string stripslashes() to return a string with backslashes stripped off htmlspecialchars() to convert special characters to HTML entities The issue is that the string that I am echoing at the end of the function is not being formatted in the way I desire at all. In fact it looks exactly the same when I run this code on my server - no white space removed, the backslash is not stripped and no special characters converted to HTML entities. My question is have I gone about this in the wrong approach? Should I be creating the variable called $santised_input on 3 separate lines with each of the functions trim(), stripslashes() and htmlspecialchars()? By my understanding surely I am overwriting the value of the $santised_input variable each time I recreate it on a new line of code. Therefore the trim() and stripslashes() string functions will never be executed. What I am trying to achieve is using the "$santised_input" variable to run all of these PHP string functions when the $data argument is passed to my test_input() function. In other words can these string functions be chained together so that I only need to create $santised_input once? <?php function test_input($data) { $santised_input = trim($data); $santised_input = stripslashes($data); $santised_input = htmlspecialchars($data); echo $santised_input; } test_input("%22%3E%3Cscript%3Ealert('hacked')%3C/script%3E\ "); //Does not output desired result "&quot;&gt;&lt;script&gt;alert('hacked')&lt;/script&gt;" ?>

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• "error: Expected a type, got 'classname'" in C++

  - by Bay

  Using the following code: template <typename T> class node { [. . .] }; class b_graph { friend istream& operator>> (istream& in, b_graph& ingraph); friend ostream& operator<< (ostream& out, b_graph& outgraph); public: [...] private: vector<node> vertices; //This line I'm getting: error: type/value mismatch at argument 1 in template parameter list for ‘template<class _Tp, class _Alloc> class std::vector’ error: expected a type, got 'node' error: template argument 2 is invalid On the indicated line. Node is clearly defined before b_graph which uses it - what have I done here?

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• how to delete a line from file using awk filtered by some string

  - by embedded

  I have a file delimited by space. I need to write an awk command that receives a host name argument and it should replace the host name if it already defined in the file. It must be a full match not partially - if the file contains this host name: localhost searching for "ho" will fail and it will be added to the end of the file. another option is a delete: again awk receives host name argument and it should remove it from the file if exists. This is what I have so far: (It needs some enhancements) if [ "$DELETE_FLAG" == "" ]; then # In this case the entry should be added or updated # if clause deals with updating an existing entry # END clause deals with adding a new entry awk -F"[ ]" "BEGIN { found = 0;} \ { \ if ($2 == $HOST_NAME) { \ print \"$IP_ADDRESS $HOST_NAME\"; \ found = 1; \ } else { \ print \$0; \ } \ } \ END { \ if (found == 0) { \ print \"$IP_ADDRESS $HOST_NAME\"; } \ } " \ /etc/hosts > /etc/temp_hosts else # Delete an existing entry awk -F'[ ]' '{if($2 != $HOST_NAME) { print $0} }' /etc/hosts > /etc/temp_hosts fi Thanks

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• Ways to make (relatively) safe assumptions about the type of concrete subclasses?

  - by Kylotan

  I have an interface (defined as a abstract base class) that looks like this: class AbstractInterface { public: bool IsRelatedTo(const AbstractInterface& other) const = 0; } And I have an implementation of this (constructors etc omitted): class ConcreteThing { public: bool IsRelatedTo(const AbstractInterface& other) const { return m_ImplObject.has_relationship_to(other.m_ImplObject); } private: ImplementationObject m_ImplObject; } The AbstractInterface forms an interface in Project A, and the ConcreteThing lives in Project B as an implementation of that interface. This is so that code in Project A can access data from Project B without having a direct dependency on it - Project B just has to implement the correct interface. Obviously the line in the body of the IsRelatedTo function cannot compile - that instance of ConcreteThing has an m_ImplObject member, but it can't assume that all AbstractInterfaces do, including the other argument. In my system, I can actually assume that all implementations of AbstractInterface are instances of ConcreteThing (or subclasses thereof), but I'd prefer not to be casting the object to the concrete type in order to get at the private member, or encoding that assumption in a way that will crash without a diagnostic later if this assumption ceases to hold true. I cannot modify ImplementationObject, but I can modify AbstractInterface and ConcreteThing. I also cannot use the standard RTTI mechanism for checking a type prior to casting, or use dynamic_cast for a similar purpose. I have a feeling that I might be able to overload IsRelatedTo with a ConcreteThing argument, but I'm not sure how to call it via the base IsRelatedTo(AbstractInterface) method. It wouldn't get called automatically as it's not a strict reimplementation of that method. Is there a pattern for doing what I want here, allowing me to implement the IsRelatedTo function via ImplementationObject::has_relationship_to(ImplementationObject), without risky casts? (Also, I couldn't think of a good question title - please change it if you have a better one.)

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• Copy object using pointer (templates)

  - by Azodious

  How the push_back of stl::vector is implemented so it can make copy of any datatype .. may be pointer, double pointer and so on ... I'm implementing a template class having a function push_back almost similar to vector. Within this method a copy of argument should be inserted in internal memory allocated memory. but the argument is a pointer. (an object pointer). Can you pls tell how to create copy from pointer. so that if i delete the pointer in caller still the copy exists in my template class? Code base is as follows: template<typename T> class Vector { public: void push_back(const T& val_in) { T* a = *(new T(val_in)); m_pData[SIZE++] = a; } } Caller: Vector<MyClass*> v(3); MyClass* a = new MyClass(); a->a = 0; a->b = .5; v.push_back(a); delete a; Thanks.

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• How can I use io.StringIO() with the csv module?

  - by Tim Pietzcker

  I tried to backport a Python 3 program to 2.7, and I'm stuck with a strange problem: >>> import io >>> import csv >>> output = io.StringIO() >>> output.write("Hello!") # Fail: io.StringIO expects Unicode Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unicode argument expected, got 'str' >>> output.write(u"Hello!") # This works as expected. 6L >>> writer = csv.writer(output) # Now let's try this with the csv module: >>> csvdata = [u"Hello", u"Goodbye"] # Look ma, all Unicode! (?) >>> writer.writerow(csvdata) # Sadly, no. Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unicode argument expected, got 'str' According to the docs, io.StringIO() returns an in-memory stream for Unicode text. It works correctly when I try and feed it a Unicode string manually. Why does it fail in conjunction with the csv module, even if all the strings being written are Unicode strings? Where does the str come from that causes the Exception? (I do know that I can use StringIO.StringIO() instead, but I'm wondering what's wrong with io.StringIO() in this scenario)

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• Confusion about pointers and their memory addresses

  - by TimothyTech

  alright, im looking at a code here and the idea is difficult to understand. #include <iostream> using namespace std; class Point { public : int X,Y; Point() : X(0), Y(0) {} }; void MoveUp (Point * p) { p -> Y += 5; } int main() { Point point MoveUp(&point) cout <<point.X << point.Y; return 0; } Alright, so i believe that a class is created and X and Y are declared and they are put inside a constructor a method is created and the argument is Point * p, which means that we are going to stick the constructor's pointer inside the function; now we create an object called point then call our method and put the pointers address inside it? isnt the pointers address just a memory number like 0x255255? and why wasnt p ever declared? (int * p = Y) what is a memory addres exactly? that it can be used as an argument?

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• How does Haskell do pattern matching without us defining an Eq on our data types?

  - by devoured elysium

  I have defined a binary tree: data Tree = Null | Node Tree Int Tree and have implemented a function that'll yield the sum of the values of all its nodes: sumOfValues :: Tree -> Int sumOfValues Null = 0 sumOfValues (Node Null v Null) = v sumOfValues (Node Null v t2) = v + (sumOfValues t2) sumOfValues (Node t1 v Null) = v + (sumOfValues t1) sumOfValues (Node t1 v t2) = v + (sumOfValues t1) + (sumOfValues t2) It works as expected. I had the idea of also trying to implement it using guards: sumOfValues2 :: Tree -> Int sumOfValues2 Null = 0 sumOfValues2 (Node t1 v t2) | t1 == Null && t2 == Null = v | t1 == Null = v + (sumOfValues2 t2) | t2 == Null = v + (sumOfValues2 t1) | otherwise = v + (sumOfValues2 t1) + (sumOfValues2 t2) but this one doesn't work because I haven't implemented Eq, I believe: No instance for (Eq Tree) arising from a use of `==' at zzz3.hs:13:3-12 Possible fix: add an instance declaration for (Eq Tree) In the first argument of `(&&)', namely `t1 == Null' In the expression: t1 == Null && t2 == Null In a stmt of a pattern guard for the definition of `sumOfValues2': t1 == Null && t2 == Null The question that has to be made, then, is how can Haskell make pattern matching without knowing when a passed argument matches, without resorting to Eq?

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• JavaScript Key Codes

  - by Jonathan Wood

  I'm working with a JavaScript routine I didn't write. It is called from a text box's onkeydown attribute to prevent unwanted keystrokes. The first argument is apparently not used. The second argument is a list of characters that should be allowed. function RestrictChars(evt, chars) { var key; var keychar; if (window.event) key = window.event.keyCode; else if (e) key = e.which; else return true; keychar = String.fromCharCode(key); if ((key == null) || (key == 0) || (key == 8) || (key == 9) || (key == 13) || (key == 27)) // Control key return true; else if (((chars).indexOf(keychar) > -1)) return true; else return false; } This seems to work for alpha-numeric characters. However, characters such as . and / cause this function to return false, even when these characters are included in the chars parameter. For example, if the . key is pressed, key is set to 190, and keychar gets set to the "3/4" character. Can anyone see how this was meant to work and/or why it doesn't? I don't know enough about JavaScript to see what it's trying to do.

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• Template specialization to use default type if class member typedef does not exist

  - by Frank

  Hi Everyone, I'm trying to write code that uses a member typedef of a template argument, but want to supply a default type if the template argument does not have that typedef. A simplified example I've tried is this: struct DefaultType { DefaultType() { printf("Default "); } }; struct NonDefaultType { NonDefaultType() { printf("NonDefault "); } }; struct A {}; struct B { typedef NonDefaultType Type; }; template<typename T, typename Enable = void> struct Get_Type { typedef DefaultType Type; }; template<typename T> struct Get_Type< T, typename T::Type > { typedef typename T::Type Type; }; int main() { Get_Type::Type test1; Get_Type::Type test2; } I would expect this to print "Default NonDefault", but instead it prints "Default Default". My expectation is that the second line in main() should match the specialized version of Get_Type, because B::Type exists. However, this does not happen. Can anyone explain what's going on here and how to fix it, or another way to accomplish the same goal? Thank you.

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• Error while saving csv file generated by PHP

  - by user1667374

  I have created below script which is saving the csv file in the same path of this script but when I am saving it to different directory, it gives me error. Can somebody please help me on this? This is the error: Warning: fopen(/store/secure/mas/) [function.fopen]: failed to open stream: No such file or directory in /getdetails.php on line 15 Warning: fputs(): supplied argument is not a valid stream resource in /getdetails.php on line 36 Warning: fclose(): supplied argument is not a valid stream resource in /getdetails.php on line 39 This is the script: <?php $MYSQL_HOST="localhost"; $MYSQL_USERNAME="***"; $MYSQL_PASSWORD="***"; $MYSQL_DATABASE="shop"; $MYSQL_TABLE="ds_orders"; mysql_connect( "$MYSQL_HOST", "$MYSQL_USERNAME", "$MYSQL_PASSWORD" ) or die( mysql_error( ) ); mysql_select_db( "$MYSQL_DATABASE") or die( mysql_error( $conn ) ); $filename="Order_Details"; $directory = "/store/secure/mas/"; $csv_filename = $filename.".csv"; $fd = fopen ( "$directory" . $cvs_filename, "w"); $today="2009-03-17"; $disp_date="05122008"; $sql = "SELECT * FROM $MYSQL_TABLE where cDate='$today'"; $result=mysql_query($sql); $rows=mysql_num_rows($result); echo $rows; if(mysql_num_rows($result)>0){ $fileContent="Record ID,Discount Percent\n"; while($data=mysql_fetch_array($result)) { $fileContent.= "".$data['oID'].",".$data['discount']."\n"; } $fileContent=str_replace("\n\n","\n",$fileContent); fputs($fd, $fileContent); } fclose($fd); ?>

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