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Search found 1102 results on 45 pages for 'recurrence relation'.

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  • has_many relation doesn't seems right or logical in business perceptive, needed some thing like belo

    - by Vijendra
    My situation is like this. Company has many users and users may belongs to many companies. And current implementation is something like below. class Company has_many :employments has_many :users, :through = :employments end class Employment belongs_to :company belongs_to :user end class User has_many :employments has_many :companies, :through = :employments #This doesn't looks correct end It works, but "user has many companies" doesn't looks logically meaningful. It must be some thing like belongs_to_many companies. Do I need to use has_and_belongs_to_many? Can some one please suggest the right way for representing these relationships?

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  • what is the relation between SIGTSTP and SIGCHLD

    - by Rawhi
    I have tow handlers for each one of them (SIGTSTP, SIGCHLD), the thing is that when I pause a process using SIGTSTP the handler function of SIGCHLD run too. what should I do to prevent this . void ExeExternal(char *args[MAX_ARG], char* cmdString, LIST_ELEMENT** pList, int *Susp_Bg_Pid, int *susp) { int pID, status, w; switch (pID = fork()) { case -1: perror("smash error: >"); break; case 0: // Child Process setpgrp(); execv(args[0], args); execvp(args[0], args); perror("error"); exit(EXIT_FAILURE); break; default: if (cmdString[strlen(cmdString) - 1] != '&') { *Susp_Bg_Pid = pID; *susp = 1; while(*susp); } else { InsertElem(pList, args[0], getpid(), pID, 0); } break; } } signal handlers : void signalHandler(int signal) { int pid, cstatus; if (signal == SIGCHLD) { susp = 0; pid = waitpid(-1, &cstatus, WNOHANG); printf("[[child %d terminated]]\n", pid); DelPID(&JobsList, pid); } } void ctrlZsignal(int signal){ kill(Susp_Bg_Pid, SIGTSTP); susp = 0; printf("\nchild %d suspended\n", Susp_Bg_Pid); } Susp_Bg_Pid used to save the paused process id. susp indicates the state of the "smash" the parent process if it is suspended or not .

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  • Database schema to store AND, OR relation, association

    - by user455387
    Many thanks for your help on this. In order for an entreprise to get a call for tender it must meet certain requirements. For the first example the enterprise must have a minimal class 4, and have qualification 2 in sector 5. Minimal class is always one number. Qualification can be anything (single, or multiple using AND, OR logical operators) I have created tables in order to map each number to it's given name. Now I need to store requirements in the database. minimal class 4 Sector Qualification 5.2 minimal class 2 Sector Qualifications 3.9 and 3.10 minimal class 3 Sector Qualifications 6.1 or 6.3 minimal class 1 Sector Qualifications (3.1 and 3.2) or 5.6 class Domain < ActiveRecord::Base has_many :domain_classes has_many :domain_sectors has_many :sector_qualifications, :through => :domain_sectors end class DomainClass < ActiveRecord::Base belongs_to :domain end class DomainSector < ActiveRecord::Base belongs_to :domain has_many :sector_qualifications end class SectorQualification < ActiveRecord::Base belongs_to :domain_sector end create_table "domains", :force => true do |t| t.string "name" end create_table "domain_classes", :force => true do |t| t.integer "number" t.integer "domain_id" end create_table "domain_sectors", :force => true do |t| t.string "name" t.integer "number" t.integer "domain_id" end create_table "sector_qualifications", :force => true do |t| t.string "name" t.integer "number" t.integer "domain_sector_id" end

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  • sql create view in one to many relation

    - by new to sql
    i want to create a view in a one-to-many relatiom. here is my relations: (a -* b) and (a -* c). i want to create a view to have this data : a1 - (all b's related to a1 + all c's relted to a1) i don't wnat sth like (a1 ,b1,c1 - a1,b1,c2 ,...) how can i create this view ?

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  • SQL: find entries in 1:n relation that don't comply with condition spanning multiple rows

    - by milianw
    I'm trying to optimize SQL queries in Akonadi and came across the following problem that is apparently not easy to solve with SQL, at least for me: Assume the following table structure (should work in SQLite, PostgreSQL, MySQL): CREATE TABLE a ( a_id INT PRIMARY KEY ); INSERT INTO a (a_id) VALUES (1), (2), (3), (4); CREATE TABLE b ( b_id INT PRIMARY KEY, a_id INT, name VARCHAR(255) NOT NULL ); INSERT INTO b (b_id, a_id, name) VALUES (1, 1, 'foo'), (2, 1, 'bar'), (3, 1, 'asdf'), (4, 2, 'foo'), (5, 2, 'bar'), (6, 3, 'foo'); Now my problem is to find entries in a that are missing name entries in table b. E.g. I need to make sure each entry in a has at least the name entries "foo" and "bar" in table b. Hence the query should return something similar to: a_id = 3 is missing name "bar" a_id = 4 is missing name "foo" and "bar" Since both tables are potentially huge in Akonadi, performance is of utmost importance. One solution in MySQL would be: SELECT a.a_id, CONCAT('|', GROUP_CONCAT(name ORDER BY NAME ASC SEPARATOR '|'), '|') as names FROM a LEFT JOIN b USING( a_id ) GROUP BY a.a_id HAVING names IS NULL OR names NOT LIKE '%|bar|foo|%'; I have yet to measure the performance tomorrow, but severly doubt it's any fast for tens of thousand of entries in a and thrice as many in b. Furthermore we want to support SQLite and PostgreSQL where to my knowledge the GROUP_CONCAT function is not available. Thanks, good night.

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  • Rails3 nomethod error #<ActiveRecord::Relation>

    - by Dodi
    Hi! I'm writing a static page controller. I get the menuname in the routes.rb and it's call the static controller show method. match '/:menuname' = 'static#show' And static_controller.rb: @static=Staticpage.where("menuname = ?", params[:menuname]) But if I want print @static.title in the view, I get this error: undefined method `title' for # Whats wrong? the SQL query looks good: SELECT staticpages.* FROM staticpages WHERE (menuname = 'asd')

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  • How to initialize list with parent child relation

    - by user2917702
    Let's say I have the following classes. public class Parent { public string name; IList<Children> children; } public class Child { public string parentName; public int age; } As it is understandable, each parent can have multiple children, and we can have multiple parents. What is the best way to initialize these classes? Is it better to get all of the parents, and all of the children from database then use LINQ? IList<Parent> parents = GetParents()//assume this gets parents from db IList<Child> children = GetChildren() //assume this gets children from db foreach(Parent parent in parents) { parent.children = children.Where(x=>x.parentName==parent.name).ToList(); } or get all of the parents and iterate through each parent to query database by parentName to get children information? Due to requirement that I have, I cannot use datatable or dataset; I can only use datareader. IList<Parent> parents = GetParents()//assume this gets parents from db foreach(Parent parent in parents) { parent.children = GetChildrenByParentName();//assume this gets parents from db by parentName } Thank you

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  • Difference between macros and functions in C in relation to instruction memory and speed

    - by DAHANS
    To my understanding the difference between a macro and a function is, that a macro-call will be replaced by the instruction in the definition, and a function does the whole push, branch and pop -thing. Is this right, or have I understand something wrong? Additionally, if this is right, it would mean, that macros would take more space, but would be faster (because of the lack of the push,branch and pop instructions.), wouldn't it?

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  • Ruby on rails edit form for has_one relation

    - by user2900873
    I have a clan.rb and clan_options.rb clan.rb class Clan < ActiveRecord::Base has_one :options, :class_name => "ClanOptions", :foreign_key => "clan_id", dependent: :destroy end clan_options.rb class ClanOptions < ActiveRecord::Base belongs_to :clan end To create an edit form for clan.rb I use the following: <%= form_for @clan, :html => {:class => 'form-horizontal'} do |clan| %> <fieldset> <!-- form stuff --> </fieldset> <% end %> It works how I want. But now I want to create an edit form for the clan_options.rb, I have no idea how to do this. If anymore information is needed to solve this, ask me.

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  • One-to-One relation classes

    - by SeyZ
    I want to have a class named ProjectDirectory and a class named MetaDirectory. Each project has a MetaDirectory which contains some meta data. Is it the good way to write the classes like this: class ProjectDirectory(object): def __init__(self, directory=None): self.directory = directory self.meta_directory = MetaDirectory(self) def __repr__(self): return self.directory class MetaDirectory(object): def __init__(self, project_directory=None): self.project_directory = project_directory self.directory = "%s/.meta/" % project_directory ProjectDirectory has a reference to MetaDirectory and MetaDirectory has a reference to ProjectDirectory. Is there an other solution or this solution is good ?

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  • Select_related() backwards relation - auto model population

    - by Nick
    Hi. If I have the following model: class Contact(models.Model) name = models.CharField(max_length=100) ... class ContactAddress(models.Model) line1 = models.CharField(max_length=100) line2 = models.CharField(max_length=100) ... contact = models.ForeignKey(Contact) I now want to grab all Contacts and for the address to be auto populated. What would be the best way to do this? The only way I have found so far is to filter out the Contacts I want and loop around each contact and assign this to Contact.addresses. I then use this for outputting each Contacts address within a template. Is there a better way of doing this? Select_related() almost does what I want, but doesn't seem to be able to work in the opposite direction. Thanks in advance for your help on this one!

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  • Unix: How to use Bash backticks recursively

    - by HH
    Either I missed some backlash or backlashing does not seem to work with too much programmer-quote-looping. $ echo "hello1-`echo hello2-\`echo hello3-\`echo hello4\`\``" hello1-hello2-hello3-echo hello4 Wanted hello1-hello2-hello3-hello4-hello5-hello6-...

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  • using onDelete with Doctrine 2

    - by tamir
    I can't get the onDelete to work in Doctrine2 (with YAML Mapping). I tried this relation in my Product class: oneToOne: category: targetEntity: Category onDelete: CASCADE But that doesn't work.. EDIT: I've set the ON DELETE: CASCADE manually in the database imported the YAML mapping with doctrine:mapping:import, emptied the database updated it from the schema with doctrine:schema:update and got no ON DELETE in the foreign key.. so looks like even Doctrine doesn't know how to do it lol..

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  • Big-O complexity of c^n + n*(logn)^2 + (10*n)^c

    - by zebraman
    I need to derive the Big-O complexity of this expression: c^n + n*(log(n))^2 + (10*n)^c where c is a constant and n is a variable. I'm pretty sure I understand how to derive the Big-O complexity of each term individually, I just don't know how the Big-O complexity changes when the terms are combined like this. Ideas? Any help would be great, thanks.

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  • Relation between " lines of the longest working program " in a language and familiarity with it?

    - by Tim
    In some computer master program online application, it says: Please list the programming languages in which you have written programs. For each language, indicate the length in lines of the longest working program you have written in that language. You may approximate, but only count those parts of the program that you wrote yourself. I don't quite remember that, and I have never counted the lines of each program. Do programmers always know approximately how many lines in each of his programs, and keep record of them? What is the relation between " lines of the longest working program " in a language and familiarity with it? Typically, how many lines will indicate the programmer being excellent, good, fair, or unfamiliar with the language? Is knowing "lines of the longest working program" really helpful?

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  • Rails Model Relationship: Has one but also belongs to many

    - by Lowgain
    I have two Models, Modela and Modelb. Modela can only own one Modelb, but Modelb can be a part of many Modela's. What I have right now is class Modela < ActiveRecord::Base has_one :modelb end class Modelb < ActiveRecord::Base belongs_to :modela, :foreign_key => "modela_id" #might not make sense? end Not too sure about the whole :foreign_key thing I was doing there, but it was where it was when I left off. As I am trying to allow Modelb to be part of many Modela's, I don't want to add a modela_id field to the Modelb table. What is the best way to do this?

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  • How to delete refClass record in Doctrine?

    - by terrani
    Hi all! I have many-to-many relations with the following tables. post tag post_tag I created three classes with Doctrine, so I have the following classes as well. BasePost BaseTag BasePostTag in the setUp() method, I defined relations. I like to delete tag record when I delete post record. So I simply put cascade as descirbed on Doctrine document. $this->hasMany("Tag as Tags",array( 'refClass' => 'PostTag', 'local'=>'object_id', 'foreign'=>'tag_id', 'cascade'=> array('delete') )); it works without a problem. My questions is, how do I delete a record from post_tag table? Do I need to create a query myself?

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  • Rails 3 query in multiple date ranges

    - by NeoRiddle
    Suppose we have some date ranges, for example: ranges = [ [(12.months.ago)..(8.months.ago)], [(7.months.ago)..(6.months.ago)], [(5.months.ago)..(4.months.ago)], [(3.months.ago)..(2.months.ago)], [(1.month.ago)..(15.days.ago)] ] and a Post model with :created_at attribute. I want to find posts where created_at value is in this range, so the goal is to create a query like: SELECT * FROM posts WHERE created_at BETWEEN '2011-04-06' AND '2011-08-06' OR BETWEEN '2011-09-06' AND '2011-10-06' OR BETWEEN '2011-11-06' AND '2011-12-06' OR BETWEEN '2012-01-06' AND '2012-02-06' OR BETWEEN '2012-02-06' AND '2012-03-23'; If you have only one range like this: range = (12.months.ago)..(8.months.ago) we can do this query: Post.where(:created_at => range) and query should be: SELECT * FROM posts WHERE created_at BETWEEN '2011-04-06' AND '2011-08-06'; Is there a way to make this query using a notation like this Post.where(:created_at => range)? And what is the correct way to build this query? Thank you

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  • generate parent child relation from the array to print a multi-level menu?

    - by Karthick Selvam
    How to get parent child relation from this array to print a multi-level menu $menus = array ( 0 => array ( 'id'=>0, 'check' => 1, 'display' =>'Arete Home', 'ordering' => -10, 'parent' => none, ), 1 => array ( 'id'=>1, 'check' => 1, 'display' => 'Submit Paper', 'ordering' => -10, 'parent' => 2, 'subordering' => -10, ), 2 => array ( 'id'=>2, 'check' => 1, 'display' => 'Buy Now', 'ordering' => -10, 'parent' => 1, 'subordering' => -10, ), 1461 => array ( 'id'=>1461, 'check' => 1, 'display' => 'Where are We?', 'ordering' => -10, 'parent' => 2, 'subordering' => -10, ), 1463 => array ( 'id'=>1463, 'check' => 1, 'display' =>' About Me?', 'ordering' => -10, 'parent' => 2, 'subordering' => -10, ), 1464 => array ( 'id'=>1464, 'check' => 1, 'display' => 'About You?', 'ordering' => -10, 'parent' => 2, 'subordering' => -10, ), 1465 => array ( 'id'=>1465, 'check' => 1, 'display' => 'About who?', 'ordering' => -10, 'parent' => 1, 'subordering' => -10, ), ); code sample: foreach($menus as $id=>$values) { $values['parent']=isset($values['parent']) ? $values['parent'] : 0; $menus[$values['parent']]['childs'][$id]=$values; unset($menus[$id]); } foreach($menus as $id1=>$value2) { $value2['parent']=isset($value2['parent']) ? $value2['parent'] : 0; $menus[$value2['parent']]['childs'][$id1]=$value2; unset($menus[$id1]); }

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