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  • Why the valid looking statement gives error in MATLAB?

    - by user198729
    It's from this question? Why the two solutions doesn't work, though it looks very valid for me: >> t = -pi:0.1:pi; >> r = ((sin(t)*sqrt(cos(t)))*(sin(t) + (7/5))^(-1)) - 2*sin(t) + 2 ; ??? Error using ==> mtimes Inner matrix dimensions must agree. >> t = -pi:0.1:pi; >> r = ((sin(t).*sqrt(cos(t))).*(sin(t) + (7/5)).^(-1)) - 2*sin(t) + 2 ; >> plot(r,t) ??? Error using ==> plot Vectors must be the same lengths. What's wrong with the above?

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  • C++ include statement required if defining a map in a headerfile.

    - by Justin
    I was doing a project for computer course on programming concepts. This project was to be completed in C++ using Object Oriented designs we learned throughout the course. Anyhow, I have two files symboltable.h and symboltable.cpp. I want to use a map as the data structure so I define it in the private section of the header file. I #include <map> in the cpp file before I #include "symboltable.h". I get several errors from the compiler (MS VS 2008 Pro) when I go to debug/run the program the first of which is: Error 1 error C2146: syntax error : missing ';' before identifier 'table' c:\users\jsmith\documents\visual studio 2008\projects\project2\project2\symboltable.h 22 Project2 To fix this I had to #include <map> in the header file, which to me seems strange. Here are the relevant code files: // symboltable.h #include <map> class SymbolTable { public: SymbolTable() {} void insert(string variable, double value); double lookUp(string variable); void init(); // Added as part of the spec given in the conference area. private: map<string, double> table; // Our container for variables and their values. }; and // symboltable.cpp #include <map> #include <string> #include <iostream> using namespace std; #include "symboltable.h" void SymbolTable::insert(string variable, double value) { table[variable] = value; // Creates a new map entry, if variable name already exist it overwrites last value. } double SymbolTable::lookUp(string variable) { if(table.find(variable) == table.end()) // Search for the variable, find() returns a position, if thats the end then we didnt find it. throw exception("Error: Uninitialized variable"); else return table[variable]; } void SymbolTable::init() { table.clear(); // Clears the map, removes all elements. }

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  • How to use T-SQL MERGE in this case?

    - by abatishchev
    I'm new to T-SQL command MERGE so I found a place in my SQL logic where I can use it and want to test it but can't figure out how exatcly should I use it: IF (EXISTS (SELECT 1 FROM commissions_history WHERE request = @requestID)) UPDATE commissions_history SET amount = @amount WHERE request = @requestID ELSE INSERT INTO commissions_history (amount) VALUES @amount) Plase suggest the proper usage. Thanks!

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  • How do I run multiple objects through an IF statement in rails?

    - by codyvbrown
    I am creating an application that highlights user messages from a stream based on whether or not the user has been 'vouched'. It works fine if it's setup for a single author. For example controller: @vouch = Vouch.last.vouched_user_nickname view: <% if tweet.from_user == @vouch %> <div class="flit_message_containerh">.... But I'm having trouble doing it for multiple user nicknames. @vouch = Vouch.find(:all, :select => "vouched_user_nickname", :group => 'vouched_user_nickname' ) Any ideas would be greatly appreciated. I'm a rails noob.

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  • How to re-enable the context menu in this case?

    - by lemonedo
    document.addEventListener('contextmenu', function (e) { e.preventDefault() e.stopPropagation() e.returnValue = false e.cancleBubble = true }) No way? Edit: document.oncontextmenu = null does not work. P.S. I cannot have the reference of the listener function since I am not the owner of the site preventing the context menu.

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  • Can I lock tables in an IF statement in MySQL?

    - by MalcomTucker
    This is throwing a syntax error - --from body of a stored proc IF (name = in_name) SET out_id = temp; ELSE LOCK TABLE People WRITE; INSERT INTO People (Name) VALUES (in_name); UNLOCK TABLE; SELECT LAST_INSERT_ID() INTO out_id END IF do I have to lock any tables I need at the start of the SP?

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  • Will lock() statement block all threads in the proccess/appdomain?

    - by MikeJ
    Maybe the question sounds silly, but I don't understand 'something about threads and locking and I would like to get a confirmation (here's why I ask). So, if I have 10 servers and 10 request in the same time come to each server, that's 100 request across the farm. Without locking, thats 100 request to the database. If I do something like this: private static readonly object myLockHolder = new object(); if (Cache[key] == null) { lock(myLockHolder) { if (Cache[key] == null) { Cache[key] = LengthyDatabaseCall(); } } } How many database requests will I do? 10? 100? Or as much as I have threads?

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  • Would Python's Twisted library be the best case for an observer type pattern?

    - by beagleguy
    hi all, I'm developing a system where a queue will be filled with millions of items I need a process that reads items from the queue constantly and then sends those items out to registered clients. I'm thinking about using twisted for this, having the queue reader be a twisted server listening on a tcp port then clients can connect on that port and when an item is pulled from the queue the server writes it out to all the clients. Does that sound like something that twisted would be ideal for? Does anyone know of any sample code out there that may do something similar? thanks

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  • Design guide-lines for writing a Typed SQL Statement API ?

    - by this. __curious_geek
    Last night I came up to sometihng intersting while designing my new project that brought me to ask this qustion here. My project is supposed to follow Table Gateway pattern using tradional ADO.Net datasets for data access. I don't want to write plain queries in my data-access classes. So I came up with an idea of writing a parser kindaa api that exposes objects and methods to generate queries on the move based on my domain objects. Later I want this api to hook up to my Business objects and provide Typed SQL generator api right on the business object instances. Any idea or references how can I do this ? This seems very wide to start with that I'm compelled take your opinions here. Does there anything already exists that can do this ?

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  • why is the Border bigger than the Group in this case?

    - by user273895
    if I place a Border with width and height of "100%" inside a Group with width and height of 10 pixels the Border looks bigger than 10 pixels, why? <s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/halo" > <s:Group width="10" height="10"> <s:Border width="100%" height="100%" borderColor="#FF0000"/> </s:Group> </s:Application>

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  • Is there a case for parameterising using Abstract classes rather than Interfaces?

    - by Chris
    I'm currently developing a component based API that is heavily stateful. The top level components implement around a dozen interfaces each. The stock top-level components therefore sit ontop of a stack of Abstract implementations which in turn contain multiple mixin implementations and implement multiple mixin interfaces. So far, so good (I hope). The problem is that the base functionality is extremely complex to implement (1,000s of lines in 5 layers of base classes) and therefore I do not wish for component writers to implement the interfaces themselves but rather to extend my base classes (where all the boiler plate code is already written). If the API therefore accepts interfaces rather than references to the Abstract implementation that I wish for component writers to extends, then I have a risk that the implementer will not perform the validation that is both required and assumed by other areas of code. Therefore, my question is, is it sometimes valid to paramerise API methods using an abstract implementation reference rather than a reference to the interface(s) that it implements? Do you have an example of a well-designed API that uses this technique or am I trying to talk myself into bad-practice?

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  • Beginner Ques::How to delete records permanently in case of linked tables?

    - by Serenity
    Let's say I have these 2 tables QuesType and Ques:- QuesType QuestypeID|QuesType |Active ------------------------------------ 101 |QuesType1 |True 102 |QuesType2 |True 103 |XXInActiveXX |False Ques QuesID|Ques|Answer|QUesTypeID|Active ------------------------------------ 1 |Ques1|Ans1 |101 |True 2 |Ques2|Ans2 |102 |True 3 |Ques3|Ans3 |101 |True In the QuesType Table:- QuesTypeID is a Primary key In the Ques Table:- QuesID is a Primary key and QuesType ID is the Foreign Key that refernces QuesTypeID from QuesType Table Now I am unable to delete records from QuesType Table, I can only make QuesType inactive by setting Active=False. I am unable to delete QuesTypes permanently because of the Foreign key relation it has with Ques Table. So , I just set the column Active=false and those Questypes then don't show on my grid wen its binded. What I want to do is be able to delete any QuesType permamnently. Now it can only be deleted if its not being used anywhere in the Ques table, right? So to delete any QuesType permanently I thot this is what I could do:- In the grid that displays QuesTypes, I have this check box for Active and a button for delete.What I thot was, when a user makes some QuesType inactive then OnCheckChanged() event will run and that will have the code to delete all the Questions in Ques table that are using that QuesTypeID. Then on the QuesType grid, that QuesType would show as Deactivated and only then can a user delete it permanently. Am I thinking correctly? Currently in my DeleteQuesType Stored Procedure what I am doing is:- Setting the Active=false and Setting QuesTye= some string like XXInactiveXX Is there any other way?

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  • Simple php statement, I can't get it to work!

    - by eberswine
    How to get $schedule = true and $schedule = true to work??? I know this is easy and I'm overlooking something simple! else { if($schedule){ $where[] = 'date > '.(time() + $config_date_adjust * 60 - 432000); } else{ $where[] = 'date < '.(time() + $config_date_adjust * 60); } $schedule = false; } else { if($schedule2){ $where[] = 'date > '.(time() + $config_date_adjust * 60 - 86400); } else{ $where[] = 'date < '.(time() + $config_date_adjust * 60); } $schedule2 = false; }

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  • What is a good use case for static import of methods?

    - by Miserable Variable
    Just got a review comment that my static import of the method was not a good idea. The static import was of a method from a DA class, which has mostly static methods. So in middle of the business logic I had a da activity that apparently seemed to belong to the current class: import static some.package.DA.*; class BusinessObject { void someMethod() { .... save(this); } } The reviewer was not keen that I change the code and I didn't but I do kind of agree with him. One reason given for not static-importing was it was confusing where the method was defined, it wasn't in the current class and not in any superclass so it too some time to identify its definition (the web based review system does not have clickable links like IDE :-) I don't really think this matters, static-imports are still quite new and soon we will all get used to locating them. But the other reason, the one I agree with, is that an unqualified method call seems to belong to current object and should not jump contexts. But if it really did belong, it would make sense to extend that super class. So, when does it make sense to static import methods? When have you done it? Did/do you like the way the unqualified calls look? EDIT: The popular opinion seems to be that static-import methods if nobody is going to confuse them as methods of the current class. For example methods from java.lang.Math and java.awt.Color. But if abs and getAlpha are not ambiguous I don't see why readEmployee is. As in lot of programming choices, I think this too is a personal preference thing. Thanks for your response guys, I am closing the question.

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  • removing a case clause: bash expansion in sed regexp: X='a\.b' ; Y=';;' sed -n '/${X}/,/${Y}/d'

    - by ChrisSM
    I'm trying to remove a case clause from a bash script. The clause will vary, but will always have backslashes as part of the case-match string. I was trying sed but could use awk or a perl one-liner within the bash script. The target of the edit is straightforward, resembles: $cat t.sh case N in a\.b); #[..etc., varies] ;; esac I am running afoul of the variable expansion escaping backslashes, semicolons or both. If I 'eval' I strip my backslash escapes. If I don't, the semi-colons catch me up. So I tried subshell expansion within the sed. This fouls the interpreter as I've written it. More escaping the semi-colons doesn't seem to help. X='a\.b' ; Y=';;' sed -i '/$(echo ${X} | sed -n 's/\\/\\\\/g')/,/$(echo ${Y} | sed -n s/\;/\\;/g')/d t.sh And this: perl -i.bak -ne 'print unless /${X}/ .. /{$Y}/' t.sh # which empties t.sh and eval perl -i.bak -ne \'print unless /${X}/ .. /{$Y}/' t.sh # which does nothing

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  • What does this statement mean ? printf("[%.*s] ", (int) lengths[i],

    - by Vivek Goel
    I was reading this page http://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html there is one line printf("[%.*s] ", (int) lengths[i], row[i] ? row[i] : "NULL"); from code MYSQL_ROW row; unsigned int num_fields; unsigned int i; num_fields = mysql_num_fields(result); while ((row = mysql_fetch_row(result))) { unsigned long *lengths; lengths = mysql_fetch_lengths(result); for(i = 0; i < num_fields; i++) { printf("[%.*s] ", (int) lengths[i], row[i] ? row[i] : "NULL"); } printf("\n"); } what does [%.*s] mean in that code ?

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  • Is there possible in clojure to make a deadlock (or anything bad case) using agents?

    - by hsestupin
    CLojure agents is powerful tool. So actions to the agents are asynchronously sent using functions "send" and "send-off". And in theory there couldn't appear something like deadlock. Is there possible to write some clojure code (for example invoking from some action another action to another agent) using agents in which we have some concurrency problem - it could be deadlock, race condition or anything else. (guys, i'm very sorry for my english)

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  • How do I run an array through an IF statement in rails?

    - by codyvbrown
    I am creating an application that highlights user messages from a stream based on whether or not the user has been 'vouched'. It works fine if it's setup for a single author. For example controller: @vouch = Vouch.last.vouched_user_nickname view: <% Twitter::Search.new(params[:id]).each do |tweet| %> <li> <%= image_tag tweet.profile_image_url %> <% if @vouch.include? tweet.from_user %> <div class="flit_message_containerh"> <u> <a href="http://twitter.com/<%= tweet.from_user %>"> <%= tweet.from_user %></a></u> <%= linkup_mentions(auto_link(h tweet.text)) %> <div class="time_ago"> <%= link_to distance_of_time_in_words_to_now(tweet.created_at) , tweet %> <% else %> <div class="flit_message_container"> <u> <a href="http://twitter.com/<%= tweet.from_user %>"> <%= tweet.from_user %></a></u> <%= linkup_mentions(auto_link(h tweet.text)) %> <div class="time_ago"> <%= link_to distance_of_time_in_words_to_now(tweet.created_at) , tweet %> <% end %> But I'm having trouble doing it for multiple user nicknames. @vouch = Vouch.find(:all, :select => "vouched_user_nickname", :group => 'vouched_user_nickname' ) Any ideas would be greatly appreciated. I'm a rails noob.

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