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  • What division operator symbol would you pick?

    - by Mackenzie
    I am currently designing and implementing a small programming language as an extra-credit project in a class I'm taking. My problem is that the language has three numeric types: Long, Double, and Fraction. Fractions can be written in the language as proper or improper fractions (e.g. "2 1/3" or "1/2"). This fact leads to problems such as "2/3.5" (Long/Double) and "2/3"(Long/Long) not being handled correctly by the lexer.The best solution that I see is to change the division operator. So far, I think "\" is the best solution since "//" starts comments. Would you pick "\", if you were designing the language? Would you pick something else? If so, what? Note: changing the way fractions are written is not possible. Thanks in advance for your help,

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  • Primary key/foreign Key naming convention

    - by Jeremy
    In our dev group we have a raging debate regarding the naming convention for Primary and Foreign Keys. There's basically two schools of thought in our group: 1) Primary Table (Employee) Primary Key is called ID Foreign table (Event) Foreign key is called EmployeeID 2) Primary Table (Employee) Primary Key is called EmployeeID Foreign table (Event) Foreign key is called EmployeeID I prefer not to duplicate the name of the table in any of the columns (So I prefer option 1 above). Conceptually, it is consisted with a lot of the recommended practices in other languages, where you don't use the name of the object in its property names. I think that naming the foreign key EmployeeID (or Employee_ID might be better) tells the reader that it is the ID column of the Employee Table. Some others prefer option 2 where you name the primary key prefixed with the table name so that the column name is the same throughout the database. I see that point, but you now can not visually distinguish a primary key from a foreign key. Also, I think it's redundant to have the table name in the column name, because if you think of the table as an entity and a column as a property or attribute of that entity, you think of it as the ID attribute of the Employee, not the EmployeeID attribute of an employee. I don't go an ask my coworker what his PersonAge or PersonGender is. I ask him what his Age is. So like I said, it's a raging debate and we go on and on and on about it. I'm interested to get some new perspective.

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  • Ruby Twitter gem

    - by jramirez
    Hi guys, I am having trouble working with the Twitter gem. I am using ruby 1.8.7 After installing when I try to run a simple script I get this error ruby twitter.rb ./twitter.rb:5: uninitialized constant Twitter (NameError) from /usr/lib/ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require' from /usr/lib/ruby/1.8/rubygems/custom_require.rb:31:inrequire' from twitter.rb:2 I running this on a Ubuntu box. I checked with gem -list and I see the Twitter (1.1.0) is listed there. this is the code I am trying to run require "rubygems" require 'twitter' puts Twitter.user_timeline("test").first.text Any ideas ?

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  • How to pass content in response from Exception filter in Asp.net WebAPI?

    - by jaffa
    Consider following code: My problem is: 1) I can't seem to cast the errors to HttpContent 2) I can't use the CreateContent extension method as this doesn't exist on the context.Response.Content.CreateContent public class ServiceLayerExceptionFilter : ExceptionFilterAttribute { public override void OnException(HttpActionExecutedContext context) { if (context.Response == null) { var exception = context.Exception as ModelValidationException; if ( exception != null ) { var modelState = new ModelStateDictionary(); modelState.AddModelError(exception.Key, exception.Description); var errors = modelState.SelectMany(x => x.Value.Errors).Select(x => x.ErrorMessage); // Cannot cast errors to HttpContent?? // var resp = new HttpResponseMessage(HttpStatusCode.BadRequest) {Content = errors}; // throw new HttpResponseException(resp); // Cannot create response from extension method?? //context.Response.Content.CreateContent } else { context.Response = new HttpResponseMessage(context.Exception.ConvertToHttpStatus()); } } base.OnException(context); } }

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  • Get latlng and draw a polyline between that two latlng

    - by anup sharma
    I have some issue in my code in that first I want to get latlng of my given address/city name from two text boxes after that i converts it to from position's latlng and to position's latlng and at last i want to draw a polyline between these point and markers on both point also, But now i am trying to draw a line between these points. But still not working this code also no any error in console also. code is here for your help. function getRoute(){ var from_text = document.getElementById("travelFrom").value; var to_text = document.getElementById("travelTo").value; if(from_text == ""){ alert("Enter travel from field") document.getElementById("travelFrom").focus(); } else if(to_text == ""){ alert("Enter travel to field"); document.getElementById("travelTo").focus(); } else{ //google.maps.event.addListener(map, "", function (e) { var myLatLng = new google.maps.LatLng(28.6667, 77.2167); var mapOptions = { zoom: 3, center: myLatLng, mapTypeId: google.maps.MapTypeId.TERRAIN }; var map = new google.maps.Map(document.getElementById('map-canvas'), mapOptions); var geocoder = new google.maps.Geocoder(); var address1 = from_text; var address2 = to_text; var from_latlng,to_latlng; //var prepath = path; //if(prepath){ // prepath.setMap(null); //} geocoder.geocode( { 'address': address1}, function(results, status) { if (status == google.maps.GeocoderStatus.OK) { // do something with the geocoded result // alert(results[0].geometry.location); from_latlng = results[0].geometry.location; // from_lat = results[0].geometry.location.latitude; // from_lng = results[0].geometry.location.longitude; // alert(from_latlng); } }); geocoder.geocode( { 'address': address2}, function(results, status) { if (status == google.maps.GeocoderStatus.OK) { // do something with the geocoded result to_latlng = results[0].geometry.location; // to_lat = results[0].geometry.location.latitude; // to_lng = results[0].geometry.location.longitude; // results[0].geometry.location.longitude // alert(to_latlng) } }); setTimeout(function(){ var flightPlanCoordinates = [ new google.maps.LatLng(from_latlng), new google.maps.LatLng(to_latlng) ]; //alert("123") var polyline; polyline = new google.maps.Polyline({ path: flightPlanCoordinates, strokeColor: "#FF0000", strokeOpacity: 1.0, strokeWeight: 2 }); polyline.setMap(map); // assign to global var path // path = polyline; },4000); // }); } }

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  • MySQL triggers cannot update rows in same table the trigger is assigned to. Suggested workaround?

    - by Cory House
    MySQL doesn't currently support updating rows in the same table the trigger is assigned to since the call could become recursive. Does anyone have suggestions on a good workaround/alternative? Right now my plan is to call a stored procedure that performs the logic I really wanted in a trigger, but I'd love to hear how others have gotten around this limitation. Edit: A little more background as requested. I have a table that stores product attribute assignments. When a new parent product record is inserted, I'd like the trigger to perform a corresponding insert in the same table for each child record. This denormalization is necessary for performance. MySQL doesn't support this and throws: Can't update table 'mytable' in stored function/trigger because it is already used by statement which invoked this stored function/trigger. A long discussion on the issue on the MySQL forums basically lead to: Use a stored proc, which is what I went with for now. Thanks in advance!

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  • Control Philips Living Colors using PC

    - by CrazyChris
    Hi guys, is there a way (hardware/software-combination) that I can use to control one or more "Philips Living Colors" lamps using a PC - e.g. a USB-stick that acts as the "remote". This way i could control the lamp through software (e.g. a web-app - over iPhone / remotely) or even create what Philips builds into some of their TVs and calls "ambilight" (graphics driver detecting the main color to control the lamp). I guess this is more like a hardware than a software question - but I couldn't find anything about this online and I'm sure not to be the first to have come up with this idea right when I unpacked my LivingColors lamp yesterday ;) Any idea/hint is appreciated. -chris

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  • Placement of defensive structures in a game

    - by Martin
    I am working on an AI bot for the game Defcon. The game has cities, with varying populations, and defensive structures with limited range. I'm trying to work out a good algorithm for placing defence towers. Cities with higher populations are more important to defend Losing a defence tower is a blow, so towers should be placed reasonably close together Towers and cities can only be placed on land So, with these three rules, we see that the best kind of placement is towers being placed in a ring around the largest population areas (although I don't want an algorithm just to blindly place a ring around the highest area of population, sometime there might be 2 sets of cities far apart, in which case the algorithm should make 2 circles, each one half my total towers). I'm wondering what kind of algorithms might be used for determining placement of towers?

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  • Postgre database ignoring created index ?!

    - by drasto
    I have an Postgre database and a table called my_table. There are 4 columns in that table (id, column1, column2, column3). The id column is primary key, there are no other constrains or indexes on columns. The table has about 200000 rows. I want to print out all rows which has value of column column2 equal(case insensitive) to 'value12'. I use this: SELECT * FROM my_table WHERE column2 = lower('value12') here is the execution plan for this statement(result of set enable_seqscan=on; EXPLAIN SELECT * FROM my_table WHERE column2 = lower('value12')): Seq Scan on my_table (cost=0.00..4676.00 rows=10000 width=55) Filter: ((column2)::text = 'value12'::text) I consider this to be to slow so I create an index on column column2 for better prerformance of searches: CREATE INDEX my_index ON my_table (lower(column2)) Now I ran the same select: SELECT * FROM my_table WHERE column2 = lower('value12') and I expect it to be much faster because it can use index. However it is not faster, it is as slow as before. So I check the execution plan and it is the same as before(see above). So it still uses sequential scen and it ignores the index! Where is the problem ?

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  • Strategy to structure a search index in a relational database

    - by neilc
    I am interested in suggestions for building an efficient and robust structure for indexing products in a new database I am building (i'm using MySql) When a product is entered through the form there are three parts I am interested in indexing for searching purposes. The product title The product description Tags The most important is title, followed by tags, followed by the description. I was thinking of using the following structure CREATE TABLE `searchindex` ( `id` INT NOT NULL , `word` VARCHAR( 255 ) NOT NULL , `weighting` INT NOT NULL , `product_id` INT NOT NULL , PRIMARY KEY ( `id` ) ) Then each time a product is created I would split apart the title, description and tags (removing common words) and award them a weighting. Then it is trivial to select out the words and corresponding products and order them by weighting. Is there a better way to do this? I would be worried that this strategy would slow down over time and as the database filled up.

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  • Low cost way to host a large table yet keep the performance scalable?

    - by Leo Liang
    I have a growing table storing time series data, 500M entries now, and 200K new records every day. The total size is around 15GB for now. My clients are querying the table via a PHP script mostly, and the size of the result set is around 10K records (not very large). select * from T where timestamp > X and timestamp < Y and additionFilters And I want this operation cheap. Currently my table is hosting in Postgres 7, on a single 16G memory Box, and I would love to see some good suggestion for me to host this in low cost and also allow me to scale up for performance if needed. The table serves: 1. Query: 90% 2. Insert: 9.9% 2. Update: 0.1% <-- very rare.

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  • Database Table Schema and Aggregate Roots

    - by bretddog
    Hi, Applicaiton is single user, 1-tier(1 pc), database SqlCE. DataService layer will be (I think) : Repository returning domain objects and quering database with LinqToSql (dbml). There are obviously a lot more columns, this is simplified view. http://img573.imageshack.us/img573/3612/ss20110115171817w.png This is my first attempt of creating a 2 tables database. I think the table schema makes sense, but I need some reassurance or critics. Because the table relations looks quite scary to be honest. I'm hoping you could; Look at the table schema and respond if there are clear signs of troubles or errors that you spot right away.. And if you have time, Look at Program Summary/Questions, and see if the table layout makes makes sense to those points. Please be brutal, I will try to defend :) Program summary: a) A set of categories, each having a set of strategies (1:m) b) Each day a number of items will be produced. And each strategy MAY reference it. (So there can be 50 items, and a strategy may reference 23 of them) c) An item can be referenced by more than one strategy. So I think it's an m:m relation. d) Status values will be logged at fixed time-fractions through the day, for: - .... each Strategy.....each StrategyItem....each item e) An action on an item may be executed by a strategy that reference it. - This is logged as ItemAction (Could have called it StrategyItemAction) User Requsts b) - e) described the main activity mode of the program. To work with only today's DayLog , for each category. 2nd priority activity is retrieval of history, which typically will be From all categories, from day x to day y; Get all StrategyDailyLog. Questions First, does the overall layout look sound? I'm worried to see that there are so many relationships in all directions, connecting everything. Is this normal, or does it look like trouble? StrategyItem is made to represent an m:m relationship. Is it correct as I noted 1:m / 1:1 (marked red) ? StrategyItemTimeLog and ItemTimeLog; Logs values that both need to be retrieved together, when retreiving a StrategyItem. Reason I separated is that the first one is strategy-specific, and several strategies can reference same item. So I thought not to duplicate those values that are not dependent no strategy, but only on the item. Hence I also dragged out the LogTime, as it seems to be the only parameter to unite the logs. But this all looks quite disturbing with those 3 tables. Does it make sense at all? Or you have suggestion? Pink circles shows my vague attempt of Aggregate Root Paths. I've been thinking in terms of "what entity is responsible for delete". Though I'm unsure about the actual root. I think it's Category. Does it make sense related to User Requests described above?

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  • Facebook writing on a wall problem - retrieves only null value.

    - by Viral
    hi all friends, I am making a game application in that I want to pass my score on wall of face book. I've completed all the things (the log in and message passing part) but when I passes the score via global variable, I am getting only null as a value and not the score that I want. Is there any way to pass data or string to Face book and write on a wall? My code is (void)viewDidLoad { static NSString* kApiKey = @"be60415be308e2b44c0ac1db83fe486b"; static NSString* kApiSecret = @"4f880c7e100321f808c41b1d3c813dfa"; _session = [[FBSession sessionForApplication:kApiKey secret:kApiSecret delegate:self] retain]; score = [NSString stringWithFormat:@"%@",appDelegate.myTextView]; [_session resume]; [super viewDidLoad]; } whre score is NSString and myTextView is NSString in other viewcontrollerfile, And appDelegate is global variable. Any help?? thanks in advance.

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  • How to model a mutually exclusive relationship in sql server

    - by littlechris
    Hi, I have to add functionality to an existing application and I've run into a data situation that I'm not sure how to model. I am being restricted to the creation of new tables and code. If I need to alter the existing structure I think my client may reject the proposal..although if its the only way to get it right this is what I will have to do. I have an Item table that can me link to any number of tables, and these tables may increase over time. The Item can only me linked to one other table, but the record in the other table may have many items linked to it. Examples of the tables/entities being linked to are "Person", "Vehicle", "Building", "Office". These are all separate tables. Example of Items are "Pen", "Stapler", "Cushion", "Tyre", "A4 Paper", "Plastic Bag", "Poster", "Decoration" For instance a "Poster" may be allocated to a "Person" or "Office" or "Building". In the future if they add a "Conference Room" table it may also be added to that. My intital thoughts are: Item { ID, Name } LinkedItem { ItemID, LinkedToTableName, LinkedToID } The LinkedToTableName field will then allow me to identify the correct table to link to in my code. I'm not overly happy with this solution, but I can't quite think of anything else. Please help! :) Thanks!

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  • How can I make a family of singletons?

    - by Jay
    I want to create a set of classes that share a lot of common behavior. Of course in OOP when you think that you automatically think "abstract class with subclasses". But among the things I want these classes to do is to each have a static list of instances of the class. The list should function as sort of a singleton within the class. I mean each of the sub-classes has a singleton, not that they share one. "Singleton" to that subclass, not a true singleton. But if it's a static, how can I inherit it? Of course code like this won't work: public abstract A { static List<A> myList; public static List getList() { if (myList==null) myList=new ArrayList<A>(10); return myList; } public static A getSomethingFromList() { List listInstance=getList(); ... do stuff with list ... } public int getSomethingFromA() { ... regular code acting against current instance ... } } public class A1 extends A { ... } public class A2 extends A { ... } A1 somethingfromA1List=(A1) A1.getSomethingFromList(); A2 somethingfromA2List=(A2) A2.getSomethingFromList(); The contents of the list for each subclass would be different, but all the code to work on the lists would be the same. The problem with the above code is that I'd only have one list for all the subclasses, and I want one for each. Yes, I could replicate the code to declare the static list in each of the subclasses, but then I'd also have to replicate all the code that adds to the lists and searches the list, etc, which rather defeats the purpose of subclassing. Any ideas on how to do this without replicating code?

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  • StockTrader RI > Controllers, Presenters, WTF?

    - by SandRock
    I am currently learning how to make advanced usage of WPF via the Prism (Composite WPF) project. I watch many videos and examples and the demo application StockTraderRI makes me ask this question: What is the exact role of each of the following part? SomethingService: Ok, this is something to manage data SomethingView: Ok, this is what's displayed SomethingPresentationModel: Ok, this contains data and commands for the view to bind to (equivalent to a ViewModel). SomethingPresenter: I don't really understand it's usage SomethingController: Don't understand too I saw that a Presenter and a Controller are not necessary but I would like to understand why they are here. Can someone tell me their role and when to use them?

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  • Sorting out POCO, Repository Pattern, Unit of Work, and ORM

    - by CoffeeAddict
    I'm reading a crapload on all these subjects: POCO Repository Pattern Unit of work Using an ORM mapper ok I see the basic definitions of each in books, etc. but I can't visualize this all together. Meaning an example structure (DL, BL, PL). So what, you have your DL objects that contain your CRUD methods, then your BL objects which are "mapped" using an ORM back to your DL objects? What about DTOs...they're your DL objects right? I'm confused. Can anyone really explain all this together or send me example code? I'm just trying to put this together. I am determining whether to go LINQ to SQL or EF 4 (not sure about NHibrernate yet). Just not getting the concepts as in physical layers and code layers here and what each type of object contains (just properties for DTOs, and CRUDs for your core DL classes that match the table fields???). I just need some guidance here. I'm reading Fowler's books and starting to read Evans but just not all there yet.

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  • Normalizing Item Names & Synonyms

    - by RabidFire
    Consider an e-commerce application with multiple stores. Each store owner can edit the item catalog of his store. My current database schema is as follows: item_names: id | name | description | picture | common(BOOL) items: id | item_name_id | picture | price | description | picture item_synonyms: id | item_name_id | name | error(BOOL) Notes: error indicates a wrong spelling (eg. "Ericson"). description and picture of the item_names table are "globals" that can optionally be overridden by "local" description and picture fields of the items table (in case the store owner wants to supply a different picture for an item). common helps separate unique item names ("Jimmy Joe's Cheese Pizza" from "Cheese Pizza") I think the bright side of this schema is: Optimized searching & Handling Synonyms: I can query the item_names & item_synonyms tables using name LIKE %QUERY% and obtain the list of item_name_ids that need to be joined with the items table. (Examples of synonyms: "Sony Ericsson", "Sony Ericson", "X10", "X 10") Autocompletion: Again, a simple query to the item_names table. I can avoid the usage of DISTINCT and it minimizes number of variations ("Sony Ericsson Xperia™ X10", "Sony Ericsson - Xperia X10", "Xperia X10, Sony Ericsson") The down side would be: Overhead: When inserting an item, I query item_names to see if this name already exists. If not, I create a new entry. When deleting an item, I count the number of entries with the same name. If this is the only item with that name, I delete the entry from the item_names table (just to keep things clean; accounts for possible erroneous submissions). And updating is the combination of both. Weird Item Names: Store owners sometimes use sentences like "Harry Potter 1, 2 Books + CDs + Magic Hat". There's something off about having so much overhead to accommodate cases like this. This would perhaps be the prime reason I'm tempted to go for a schema like this: items: id | name | picture | price | description | picture (... with item_names and item_synonyms as utility tables that I could query) Is there a better schema you would suggested? Should item names be normalized for autocomplete? Is this probably what Facebook does for "School", "City" entries? Is the first schema or the second better/optimal for search? Thanks in advance! References: (1) Is normalizing a person's name going too far?, (2) Avoiding DISTINCT

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  • Cleanly handling events

    - by nkr1pt
    I have code similar to this in all my observer classes that handle events fired by an event bus class. As you can see there are a lot of instanceof checks to choose the path of action needed to appropriately handle events, and I was wondering if this could be done more cleanly, eliminating the instanceof tests? @Override public void handleEvent(Event event) { if (event instanceof DownloadStartedEvent) { DownloadStartedEvent dsEvent = (DownloadStartedEvent)event; dsEvent.getDownloadCandidateItem().setState(new BusyDownloadingState()); } else if (event instanceof DownloadCompletedEvent) { DownloadCompletedEvent dcEvent = (DownloadCompletedEvent)event; dcEvent.getDownloadCandidateItem().setState(new FinishedDownloadingState()); DownloadCandidate downloadCandidate = dcEvent.getDownloadCandidateItem(). getDownloadCandidate(); if (downloadCandidate.isComplete()) { // start extracting } } else if (event instanceof DownloadFailedEvent) { DownloadFailedEvent dfEvent = (DownloadFailedEvent)event; dfEvent.getDownloadCandidateItem().setState(new FailedDownloadingState()); } }

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  • Database: relational/not relational/object oriented... What to choose?

    - by Damian
    I'm porting a website that I made for app engine to run on a dedicated server. It is coded in java and I'm looking for a database to replace google datastore. My first thougt was MySql because everybody uses it, but i dont like SQL and I think I would feel more comfortable using OODB or anything else. With google datastore I could modify my models and don't worry about the database definition at all. I know using MySql that isn't possible. And I don't want to miss that. And if I use a OODB, which should I use? What about performance compared to MySql? Well, any idea or tip will really help me since I know nothing about databases.

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  • smallest mysql type that accomodates single decimal

    - by donpal
    Database newbie here. I'm setting up a mysql table. One of the fields will accept a value in increment of a 0.5. e.g. 0.5, 1.0, 1.5, 2.0, .... 200.5, etc. I've tried int but it doesn't capture the decimals. `value` int(10), What would be the smallest type that can accommodate this value, considering it's only a single decimal. I also was considering that because the decimal will always be 0.5 if at all, I could store it in a separate boolean field? So I would have 2 fields instead. Is this a stupid or somewhat over complicated idea? I don't know if it really saves me any memory, and it might get slower now that I'm accessing 2 fields instead of 1 `value` int(10), `half` bool, //or something similar to boolean What are your suggestions guys? Is the first option better, and what's the smallest data type in that case that would get me the 0.5?

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  • Google Maps InfoBubble pixelOffset

    - by Sam
    I am trying to implement a custom infoBubble that has the box opening to the side of a marker. This has turned out to be harder than expected. Using the normal infoWindow you can use pixelOffset. See here for the documentation Using infoBubble this does not seem to be the case. Is there anyway of using pixelOffset in an infoBubble, or something that will do the same thing? I have found this very difficult to search for, as using a google search such as this returns no relevant results Google Search Below is all my resources I have been using. Example of infoBubble here. My JavaScript to setup the map and infoBubble here. And now my javascript here just in-case the jsfiddle link is broken. <script type="text/javascript"> $(document).ready(function () { init(); }); function init() { //Setup the map var googleMapOptions = { center: new google.maps.LatLng(53.5167, -1.1333), zoom: 13, mapTypeId: google.maps.MapTypeId.ROADMAP }; //Start the map var map = new google.maps.Map(document.getElementById("map_canvas"), googleMapOptions); var marker = new google.maps.Marker({ position: new google.maps.LatLng(53.5267, -1.1333), title: "Just a test" }); marker.setMap(map); infoBubble = new InfoBubble({ map: map, content: '<div class="phoneytext">Some label</div>', //position: new google.maps.LatLng(-35, 151), shadowStyle: 1, padding: '10px', //backgroundColor: 'rgb(57,57,57)', borderRadius: 5, minWidth: 200, arrowSize: 10, borderWidth: 1, borderColor: '#2c2c2c', disableAutoPan: true, hideCloseButton: false, arrowPosition: 7, backgroundClassName: 'phoney', pixelOffset: new google.maps.Size(130, 120), arrowStyle: 2 }); infoBubble.open(map, marker); } </script>

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  • Is there a programming language that performs currying when named parameters are omitted?

    - by Adam Gent
    Many functional programming languages have support for curried parameters. To support currying functions the parameters to the function are essentially a tuple where the last parameter can be omitted making a new function requiring a smaller tuple. I'm thinking of designing a language that always uses records (aka named parameters) for function parameters. Thus simple math functions in my make believe language would be: add { left : num, right : num } = ... minus { left : num, right : num } = .. You can pass in any record to those functions so long as they have those two named parameters (they can have more just "left" and "right"). If they have only one of the named parameter it creates a new function: minus5 :: { left : num } -> num minus5 = minus { right : 5 } I borrow some of haskell's notation for above. Has any one seen a language that does this?

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