Search Results

Search found 18729 results on 750 pages for 'edit'.

Page 629/750 | < Previous Page | 625 626 627 628 629 630 631 632 633 634 635 636  | Next Page >

  • How to Implement an Interface that Requires Duplicate Member Names?

    - by Will Marcouiller
    I often have to implement some interfaces such as IEnumerable<T> in my code. Each time, when implementing automatically, I encounter the following: public IEnumerator<T> GetEnumerator() { // Code here... } public IEnumerator GetEnumerator1() { // Code here... } Though I have to implement both GetEnumerator() methods, they impossibly can have the same name, even if we understand that they do the same, somehow. The compiler can't treat them as one being the overload of the other, because only the return type differs. When doing so, I manage to set the GetEnumerator1() accessor to private. This way, the compiler doesn't complaint about not implementing the interface member, and I simply throw a NotImplementedException within the method's body. However, I wonder whether it is a good practice, or if I shall proceed differently, as perhaps a method alias or something like so. What is the best approach while implementing an interface such as IEnumerable<T> that requires the implementation of two different methods with the same name? EDIT #1 Does VB.NET reacts differently from C# while implementing interfaces, since in VB.NET it is explicitly implemented, thus forcing the GetEnumerator1(). Here's the code: Public Function GetEnumerator() As System.Collections.Generic.IEnumerator(Of T) Implements System.Collections.Generic.IEnumerable(Of T).GetEnumerator // Code here... End Function Public Function GetEnumerator1() As System.Collections.Generic.IEnumerator Implements System.Collections.Generic.IEnumerable.GetEnumerator // Code here... End Function Both GetEnumerator() methods are explicitly implemented, and the compile will refuse them to have the same name. Why?

    Read the article

  • S3 file Uploading from Mac app though PHP?

    - by Ilija Tovilo
    I have asked this question before, but it was deleted due too little information. I'll try to be more concrete this time. I have an Objective-C mac application, which should allow users to upload files to S3-storage. The s3 storage is mine, the users don't have an Amazon account. Until now, the files were uploaded directly to the amazon servers. After thinking some more about it, it wasn't really a great concept, regarding security and flexibility. I want to add a server in between. The user should authenticate with my server, the server would open a session if the authentication was successful, and the file-sharing could begin. Now my question. I want to upload the files to S3. One option would be to make a POST-request and wait until the server would receive the file. Problems here are, that there would be a delay, when the file is being uploaded from my server to the S3 servers, and it would double the uploading time. Best would be, if I could validate the request, and then redirecting it, so the client uploads it directly to the s3-storage. Not sure if this is possible somehow. Uploading directly to S3 doesn't seem to be very smart. After looking into other apps like Droplr and Dropmark, it looks like they don't do this. Btw. I did this using Little Snitch. They have their api on their own web-server, and that's it. Could someone clear things up for me? EDIT How should I transmit my files to S3? Is there a way to "forward" it, or do I have to upload it to my server and then upload it from there to S3? Like I said, other apps can do this efficiently and without the need of communicating with S3 directly.

    Read the article

  • How do I stop Chrome from yellowing my site's input boxes?

    - by davebug
    Among other text and visual aids on a form submission, post-validation, I'm coloring my input boxes red to signify the interactive area needing attention. On Chrome (and for Google Toolbar users) the auto-fill feature re-colors my input forms yellow. Here's the complex issue: I want auto-complete allowed on my forms, as it speeds users logging in. I am going to check into the ability to turn the autocomplete attribute to off if/when there's an error triggered, but it is a complex bit of coding to programmatically turn off the auto-complete for the single effected input on a page. This, to put it simply, would be a major headache. So to try to avoid that issue, is there any simpler method of stopping Chrome from re-coloring the input boxes? [edit] I tried the !important suggestion below and it had no effect. I have not yet checked Google Toolbar to see if the !important attribute woudl work for that. As far as I can tell, there isn't any means other than using the autocomplete attribute (which does appear to work).

    Read the article

  • Which class should store the lookup table?

    - by max
    The world contains agents at different locations, with only a single agent at any location. Each agent knows where he's at, but I also need to quickly check if there's an agent at a given location. Hence, I also maintain a map from locations to agents. I have a problem deciding where this map belongs to: class World, class Agent (as a class attribute) or elsewhere. In the following I put the lookup table, agent_locations, in class World. But now agents have to call world.update_agent_location every time they move. This is very annoying; what if I decide later to track other things about the agents, apart from their locations - would I need to add calls back to the world object all across the Agent code? class World: def __init__(self, n_agents): # ... self.agents = {} self.agent_locations = {} for id in range(n_agents): x, y = self.find_location() agent = Agent(self,x,y) self.agents.append(agent) self.agent_locations[x,y] = agent def update_agent_location(self, agent, x, y): del self.agent_locations[agent.x, agent.y] self.agent_locations[x, y] = agent def update(self): # next step in the simulation for agent in self.agents: agent.update() # next step for this agent # ... class Agent: def __init__(self, world, x, y): self.world = world self.x, self.y = x, y def move(self, x1, y1): self.world.update_agent_location(self, x1, y1) self.x, self.y = x1, y1 def update(): # find a good location that is not occupied and move there for x, y in self.valid_locations(): if not self.location_is_good(x, y): continue if self.world.agent_locations[x, y]: # location occupied continue self.move(x, y) I can instead put agent_locations in class Agent as a class attribute. But that only works when I have a single World object. If I later decide to instantiate multiple World objects, the lookup tables would need to be world-specific. I am sure there's a better solution... EDIT: I added a few lines to the code to show how agent_locations is used. Note that it's only used from inside Agent objects, but I don't know if that would remain the case forever.

    Read the article

  • C++ meta-splat function

    - by aaa
    hello. Is there an existing function (in boost mpl or fusion) to splat meta-vector to variadic template arguments? for example: splat<vector<T1, T2, ...>, function>::type same as function<T1, T2, ...> my search have not found one, and I do not want to reinvent one if it already exists. edit: after some tinkering, apparently it's next to impossible to accomplish this in general way, as it would require declaring full template template parameter list for all possible cases. only reasonable solution is to use macro: #define splat(name, function) \ template<class T, ...> struct name; \ template<class T> \ struct name<T,typename boost::enable_if_c< \ result_of::size<T>::value == 1>::type> { \ typedef function< \ typename result_of::value_at_c<T,0>::type \ > type; \ }; Oh well. thank you

    Read the article

  • Best implementation of Java Queue?

    - by Georges Oates Larsen
    I am working (In java) on a recursive image processing algorithm that recursively traverses the pixels of the image, outward from a center point. Unfortunately... That causes stack overflows, so I have decided to switch to a Queue-based algorithm. Now, this is all fine and dandy -- But considering the fact that its queue will be analyzing THOUSANDS of pixels in a very short amount of time, while constantly popping and pushing, WITHOUT maintaining a predictable state (It could be anywhere between length 100, and 20000); The queue implementation needs to have significantly fast popping and pushing abilities. A linked list seems attractive due to its ability to push elements unto its self without rearranging anything else in the list, but in order for it to be fast enough, it would need easy access to both its head, AND its tail (or second-to-last node if it were not doubly-linked). Sadly, though I cannot find any information related to the underlying implementation of linked lists in Java, so it's hard to say if a linked list is really the way to go... This brings me to my question... What would be the best implementation of the Queue interface in Java for what I intend to do? (I do not wish to edit or even access anything other than the head and tail of the queue -- I do not wish to do any sort of rearranging, or anything. On the flip side, I DO intend to do a lot of pushing and popping, and the queue will be changing size quite a bit, so preallocating would be inefficient)

    Read the article

  • Visual Studio 2010 / ASP.NET MVC 2 / Publish

    - by SevenCentral
    I just did a clean install on Windows 7 x64 Professional with the final release of Visual Studio 2010 Premium. In order to duplicate what I'm experiencing do the following in: Create a new ASP.NET MVC 2 Web Application Right click the project and select Properties On the Web tab, select "Use Local IIS Web Server" Click on Create Virtual Directory Save all Unload the project Edit the project file Change MvcBuildViews to true Save all Reload project Right click the project and select Publish Choose the file system publish method Enter a target location Choose Delete all existing files Select Publish Right click the project Select Publish Each time I do the above I get the following errror: "It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level..." The error originates from obj\debug\package\packagetmp\web.config, relative to the project directory. I can repeat this all day long with any MVC 2 project I've built. In order to fix this problem, I need to set MvcBuildViews to false in the project file. That's not really an option. This wasn't a problem in Visual Studio 2008 and it seems to be an issue with the way the Publish command stages files beneath the project directory. Can anyone else duplicate this error? Is this a bug or by design? Is there a fix, workaround, etc...? Thanks.

    Read the article

  • PHP question about global variables and form requests

    - by user220201
    Hi, This is probably a stupid question but will ask anyway sine I have no idea. I have written basic php code which serve forms. Say I have a login page and I serve it using the login.php page and it will be called in the login.html page like this - <form action="login.php" method="post"> By this it is also implied that every POST needs its own php file, doesn't it? This kind of feels weird. Is there a way to have a single file, say code.php, and just have each of the forms as functions instead? EDIT: Specifically, say I have 5 forms that are used one after the other in my application. Say after login the user does A, B, C and D tasks each of which are sent to the server as a POST request. So instead of having A.php, B.php, C.php and D.php I would like to have a single code.php and have A(), B(), C() and D() as functions. Is there a way to do this? Also on the same note, how do I deal with say a global array (e.g. an array of currently logged in users) across multiple forms? I want to do this without writing to a DB. I know its probably better to write to a DB and query but is it even possible to do it with a global array? The reason I was thinking about having all the form functions in one file is to use a global array. Thanks, - Pav

    Read the article

  • How to query the SPView object

    - by Hugo Migneron
    I have a SPView object that contains a lot of SPListItem objects (there are many fields in the view). I am only interested in one of these fields. Let's call it specialField Given that view and specialField, I want to know if a value is contained in specialField. Here is a way of doing what I want to do : String specialField = "Special Field"; String specialValue = "value"; SPList list = SPContext.Current.Site.RootWeb.Lists["My List"]; SPView view = list.Views["My View"]; //This is the view I want to query SPQuery query = new SPQuery(); query.Query = view.Query; SPListItemCollection items = list.GetItems(query); foreach(SPListItem item in items) { var value = item[specialField]; if(value != null) && (value.ToString() == specialValue) { //My value is found. This is what I was looking for. //break out of the loop or return } } //My value is not found. However, iterating through each ListItem hardly seems optimal, especially as there might be hundreds of items. This query will be executed often, so I am looking for an efficient way to do this. EDIT I will not always be working with the same view, so my solution cannot be hardcoded (it has to be generic enough that the list, view and specialField can be changed.

    Read the article

  • How to unit test generic classes

    - by Rowland Shaw
    I'm trying to set up some unit tests for an existing compact framework class library. However, I've fallen at the first hurdle, where it appears that the test framework is unable to load the types involved (even though they're both in the class library being tested) Test method MyLibrary.Tests.MyGenericClassTest.MyMethodTest threw exception: System.MissingMethodException: Could not load type 'MyLibrary.MyType' from assembly 'MyLibrary, Version=1.0.3778.36113, Culture=neutral, PublicKeyToken=null'.. My code is loosely: public class MyGenericClass<T> : List<T> where T : MyType, new() { public bool MyMethod(T foo) { throw new NotImplementedException(); } } With test methods: public void MyMethodTestHelper<T>() where T : MyType, new() { MyGenericClass<T> target = new MyGenericClass<T>(); foo = new T(); expected = true; actual = target.MyMethod(foo); Assert.AreEqual(expected, actual); } [TestMethod()] public void MyMethodTest() { MyMethodTestHelper<MyType>(); } I'm a bit stumped though, as I can't even get it to break in the debugger to get to the inner exception, so what else do I check? EDIT this does seem to be something specific to the Compact Framework - recompiling the class libraries and the unit tests for the full framework, gives the expected output (i.e. the debugger stops when I'm going to throw a NotImplementedException).

    Read the article

  • How can I control UISlider Value Changed-events frequncy?

    - by Albert
    I'm writing an iPhone app that is using two uisliders to control values that are sent using coreBluetooth. If I move the sliders quickly one value freezes at the receiver, presumably because the Value Changed events trigger so often that the write-commands stack up and eventually get thrown away. How can I make sure the events don't trigger too often? Edit: Here is a clarification of the problem; the bluetooth connection sends commands every 105ms. If the user generates a bunch of events during that time they seem to que up. I would like to throw away any values generated between the connection events and just send one every 105ms. This is basically what I'm doing right now: -(IBAction) sliderChanged:(UISlider *)sender{ static int8_t value = 0; int8_t new_value = (int8_t)sender.value; if ( new_value > value + threshold || new_value < value - threshold ) { value = new_value; [btDevice writeValue:value]; } } What I'm asking is how to implement something like -(IBAction) sliderChanged:(UISlider *)sender{ static int8_t value = 0; if (105msHasPassed) { int8_t new_value = (int8_t)sender.value; if ( new_value > value + threshold || new_value < value - threshold ) { value = new_value; [btDevice writeValue:value]; } } }

    Read the article

  • [solved] IE6 PNG-transparency CSS hack not working

    - by John
    I looked around and decided to use a CSS approach rather than rely on JS... I figure the kind of corporate users stuck with IE6 might also have JS disabled by IT departments. So In my HTML I have: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta http-equiv="Content-Type" content="text/html;charset=utf-8" /> <title>My Page</title> <link rel="stylesheet" type="text/css" href="default.css" /> <!--[if IE 6]><link rel="stylesheet" type="text/css" href="ie6.css"><![endif]--> </head> <body> <img src="media/logo.png"/> </body> Then my ie6.css consists simply of: img { filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(...); } However none of this makes the slightest difference, no transparency. I commented out all the rest of the page so it is literally that one and still no luck. I removed the default.css stylesheet and still no difference. EDIT: I now got it working, using the .htc method, loading that file in a conditional IE6 test block. It turned out the problem I was having was that Windows 7 had 'locked' the file (I don't even know what this means) and this blocked IE from loading/using it.

    Read the article

  • webpart context.session is null

    - by tbischel
    I've been using the session array to store a state variable for my webpart... so I have a property like this: public INode RootNode { get { return this.Context.Session["RootNode"] as INode; } set { this.Context.Session["RootNode"] = value as object; } } This usually works fine. I've discovered that sometimes, the context.session variable will be null. I'd like to know what are the conditions that cause the session to be null in the first place, and whats the best way to persist my object when this happens? Can I just assign a new HttpSessionState object to the context, or does that screw things up? Edit: Ok, so its not just the session that is null... the whole context is screwed up. When the webpart enters the init, the context is fine... but when it reaches the dropbox selectedindexchange postback event (the dropbox contains node id's to use to set the rootnode variable), the context contains mostly null properties. also, it only seems to happen when certain id's are selected. This looks more like some kind of weird bug on my end than a problem with my understanding of the session.

    Read the article

  • Why does mobile first responsive design tend to not use max-width queries alongside the min-width queries?

    - by Sam
    First off, I understand the basic principles behind mobile first responsive web design, and totally agree with them. But one thing I don't understand: In my experience, not all styles for small screens can be used for the larger version of a website. For example, usually smaller versions tend to have larger clickable areas, hamburger navigation, etc. So I sometimes have to override these specific styles, aside from just progressively enhancing the base styles. So I was wondering: why is max-width rarely mentioned (or used) in the context of mobile-first responsive web design? Because it looks like it could be used to isolate styles for smaller screens that are not useful for larger screens, and would thus prevent unnecessary duplication of code. A quote which mentions min-width as typically mobile-first, but not max-width: Mobile first, from a coding perspective, means that your base style is typically a single-column, fully-fluid layout. You use @media (min-width: whatever) to add a grid-based layout on top of that. from: http://gomakethings.com/mobile-first-and-internet-explorer/ EDIT: So to be more specific: I was wondering if there is a reason to exclude max-width from a mobile-first responsive design (as it seems like it can be useful for writing your css as DRY as possible, as some styles for small screens will not be used for bigger screens).

    Read the article

  • How can I send multiple images in a server push Perl CGI program?

    - by Jujjuru
    I am a beginner in Perl CGI etc. I was experimenting with server-push concept with a piece of Perl code. It is supposed to send a jpeg image to the client every three seconds. Unfortunately nothing seems to work. Can somebody help identify the problem? Here is the code: use strict; # turn off io buffering $|=1; print "Content-type: multipart/x-mixed-replace;"; print "boundary=magicalboundarystring\n\n"; print "--magicalboundarystring\n"; #list the jpg images my(@file_list) = glob "*.jpg"; my($file) = ""; foreach $file(@file_list ) { open FILE,">", $file or die "Cannot open file $file: $!"; print "Content-type: image/jpeg\n\n"; while ( <FILE> ) { print "$_"; } close FILE; print "\n--magicalboundarystring\n"; sleep 3; next; } EDIT: added turn off i/o buffering, added "use strict" and "@file_list", "$file" are made local

    Read the article

  • Incrementing value by one over a lot of rows

    - by Andy Gee
    Edit: I think the answer to my question lies in the ability to set user defined variables in MySQL through PHP - the answer by Multifarious has pointed me in this direction Currently I have a script to cycle over 10M records, it's very slow and it goes like this: I first get a block of 1000 results in an array similar to this: $matches[] = array('quality_rank'=>46732, 'db_id'=>5532); $matches[] = array('quality_rank'=>12324, 'db_id'=>1234); $matches[] = array('quality_rank'=>45235, 'db_id'=>8345); $matches[] = array('quality_rank'=>75543, 'db_id'=>2562); I then cycle through them one by one and update the record $mult = count($matches)*2; foreach($matches as $m) { $rank++; $score = (($m[quality_rank] + $rank)/($mult))*100; $s = "UPDATE `packages_sorted` SET `price_rank` = '".$rank."', `deal_score` = '".$score."' WHERE `db_id` = '".$m[db_id]."' LIMIT 1"; } It seems like this is a very slow way of doing it but I can't find another way to increment the field price_rank by one each time. Can anyone suggest a better method. Note: Although I wouldn't usually store this kind of value in a database I really do need on this occasion for comparison search queries later on in the project. Any help would be kindly appreciated :)

    Read the article

  • Android: Adding header to dynamic listView

    - by cg5572
    I'm still pretty new to android coding, and trying to figure things out. I'm creating a listview dynamically as shown below (and then disabling items dynamically also) - you'll notice that there's no xml file for the activity itself, just for the listitem. What I'd like to do is add a static header to the page. Could someone explain to me how I can modify the code below to EITHER add this programatically within the java file, before the listView, OR edit the code below so that it targets a listView within an xml file! Help would be much appreciated!!! public class Start extends ListActivity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); DataBaseHelper myDbHelper = new DataBaseHelper(null); myDbHelper = new DataBaseHelper(this); try { myDbHelper.openDataBase(); }catch(SQLException sqle){ throw sqle; } ArrayList<String> categoryList = new ArrayList<String>(); Cursor cur = myDbHelper.getAllCategories(); cur.moveToFirst(); while (cur.isAfterLast() == false) { if (!categoryList.contains(cur.getString(1))) { categoryList.add(cur.getString(1)); } cur.moveToNext(); } cur.close(); Collections.sort(categoryList); setListAdapter(new ArrayAdapter<String>(this, R.layout.listitem, categoryList) { @Override public View getView(int position, View convertView, ViewGroup parent) { View view = super.getView(position, convertView, parent); if(Arrays.asList(checkArray3).contains(String.valueOf(position))){ view.setEnabled(false); } else { view.setEnabled(true); } return view; } }); } @Override protected void onListItemClick(ListView l, View v, int position, long id) { if(v.isEnabled()) { String clickedCat = l.getItemAtPosition(position).toString(); Toast.makeText(this, clickedCat, Toast.LENGTH_SHORT).show(); finish(); Intent myIntent = new Intent(getApplicationContext(), Questions.class); myIntent.putExtra("passedCategory", clickedCat); myIntent.putExtra("startTrigger", "go"); startActivity(myIntent); } } }

    Read the article

  • Load more function in Javascript

    - by erastusnjuki
    EDIT: This question was initially too general, I think. So What I really need is a very good tutorial on how to implement the Load More function on Safari for iPhone just like the Twitter website(mobile.twitter.com) does. Just a wordpress plugin won't really help. But if the plugin is well explained, like if it is wptouch, home(that also has this function) that can also do. I know that it doesn't really matter that it is being displayed on a mobile device, but the point I am stressing is that if such a function is well explained, then it will be up to me to know how to customize it to suit me. I am using a javascript function to load entries that come from the database dynamically, so that content opens in the same page (like with twitter(tweets feed) and facebook(news feed)). The php/html version(That opens a page in a new tab) is echo '<a href="http://'. $_SERVER['HTTP_HOST'] .'/'.$domain_page.'?form='.$form_id.'&page='.($page+1).'">Load more entries&rsaquo; </a>'; The javascript/ajax version: <div id="call_hv<?php echo md5($_SERVER['REQUEST_URI']); ?>" class="ajax-load-more"> <img id="spinner<?php echo md5($_SERVER['REQUEST_URI']); ?>" class="spin" src="<?php bloginfo('template_directory'); ?>/images/main-ajax-loader.gif" style="display:none" alt="" /> <a class="ajax" href="javascript:$ajax_hv('#spinner<?php echo md5($_SERVER['REQUEST_URI']); ?>').fadeIn(200); $ajax_hv('#ajaxentries_hv<?php echo md5($_SERVER['REQUEST_URI']); ?>').load('form='<? echo $form_id; ?>&page=<?php echo $page+1;?>', {}, function(){ $ajax_hv('#call_hv<?php echo md5($_SERVER['REQUEST_URI']); ?>').fadeOut();})">Load more entries... </a>

    Read the article

  • Approaches for animating a C# property over time?

    - by Mario Fritsch
    I'm currently trying to animate a bunch of public properties on certain objects. Usually they are of type float or vectors of floats (the type is known at compile-time). I want to be able to: assign a static value to them (MyObject.Duration = 10f;) or assign a random value to them by specifying a minimum and maximum value and optionally also a weight (MyObject.Duration = new RandomFloat(5f, 20f, 2f);) or "bind" this property to the property of another object (think of a child object binding some of its properties to its parent object, like its color or size or sth.) or assign sort of a keyframe animation to them, specifying a variable number of keyframes with timecode and the property's value at that specific point in time as well as information about how to interpolate between these frames The keyframes should be able to accept random values for each frame, both for the time and the property's value. What would be a practical approach for this kind of system? Currently I'm thinking about polymorphism: implement a base class or interface with a public Value-property and/or GetValue(float time)-method and then creating different sub classes like StaticValue, RandomValue, BindingValue and AnimatedValue implementing this base class or interface. Doesn't seem very elegant, though, and the initialization of even simple objects becomes a bit tedious. Another idea would be to implement these properties just as regular floats or vectors and create special "Modifier"-types binding to these properties. To retrieve the "real" value of the property, I'd first call any Modifier bound to the property, which would in turn update the actual object's property for me to retrieve later on. That would most likely mean using reflection at some point, which could be quite bad for performance as I'll probably have thousands of properties to update dozens of times per second. Any suggestions on this? Being a novice I'm (hopefully) missing some far more elegant and/or practical solution than I'm already playing around with :( Edit: Probably should have mentioned this earlier, but WPF isn't an option - it's not available on all targetted platforms, so I can't rely on it. I'm aware of its powerful databinding and animation capabilities, but I need to roll my own (or find some other lightweight alternative meeting my needs).

    Read the article

  • Browser download file prompt using javascript

    - by aix
    hi, I was wondering if there was any method to implement browser's download file prompt using javascript. My reason - well users will be uploading files to a local fileserver which cannot be accessed from the webserver. In other words, both will be on different domains! e.g. let’s say websites hosted on www.xyz.com, but files would reside on local file server with address like \10.10.10.01\Files\file.txt. How am I uploading/transferring file to local fileserver... using ACTIVEX(yikes) & VBscript!!!! (don’t ask :-) so i am storing local file path in my database and binding that data to a grid. So when the user clicks on that link, the file opens in a window (using javascript). Problem is certain file types like text, jpg, pdf, etc open inside browser window. How would i be able to implement content-type or content-disposition using client side scripting? Is that even possible? hoping my description was clear. Any ideas? EDIT: the local file server has a window's shared folder on which the files are saved.

    Read the article

  • Why does this Haskell code produce the "infinite type" error?

    - by Charlie Flowers
    I am new to Haskell and facing a "cannot construct infinite type" error that I cannot make sense of. In fact, beyond that, I have not been able to find a good explanation of what this error even means, so if you could go beyond my basic question and explain the "infinite type" error, I'd really appreciate it. Here's the code: intersperse :: a -> [[a]] -> [a] -- intersperse '*' ["foo","bar","baz","quux"] -- should produce the following: -- "foo*bar*baz*quux" -- intersperse -99 [ [1,2,3],[4,5,6],[7,8,9]] -- should produce the following: -- [1,2,3,-99,4,5,6,-99,7,8,9] intersperse _ [] = [] intersperse _ [x] = x intersperse s (x:y:xs) = x:s:y:intersperse s xs And here's the error trying to load it into the interpreter: Prelude :load ./chapter.3.ending.real.world.haskell.exercises.hs [1 of 1] Compiling Main ( chapter.3.ending.real.world.haskell.exercises.hs, interpreted ) chapter.3.ending.real.world.haskell.exercises.hs:147:0: Occurs check: cannot construct the infinite type: a = [a] When generalising the type(s) for `intersperse' Failed, modules loaded: none. Thanks. EDIT: Thanks to the responses, I have corrected the code and I also have a general guideline for dealing with the "infinite type" error in Haskell: Corrected code intersperse _ [] = [] intersperse _ [x] = x intersperse s (x:xs) = x ++ s:intersperse s xs What the problem was: My type signature states that the second parameter to intersperse is a list of lists. Therefore, when I pattern matched against "s (x:y:xs)", x and y became lists. And yet I was treating x and y as elements, not lists. Guideline for dealing with the "infinite type" error: Most of the time, when you get this error, you have forgotten the types of the various variables you're dealing with, and you have attempted to use a variable as if it were some other type than what it is. Look carefully at what type everything is versus how you're using it, and this will usually uncover the problem.

    Read the article

  • .NET TCP Client/Server communication issue

    - by Jamie
    What I'm currently trying to do is make a very basic webchat for irc using silverlight. Basically how I'm trying to do it is have a tcp server listening for connections from silverlight. When a client connects it creates a new connection to irc and data is passed to/from the client/irc via the server application. I've gotten it to work fine for one client connection, but as soon as two (or more) clients connect multiple connections are made to irc but all data passed from the clients just goes through the latest irc connection (if that makes sense). For example Client1, Client2 and Client3 are all connected to irc, but no matter who sends data it all comes through Client3. Between the client and server app it recognizes the data coming in from different clients so i believe the problems lies within the way I've connected to the irc. When the TCP server accepts a new client a new thread is made to listen to incoming data, and from there a new thread is made to connect to irc. I'm sure thats where the problem exists, but I've confused myself a lot now and am wondering if anyone can help me figure out a solution. EDIT: What I think is the problem, is that it can't distinguish which thread the specific client is using, so it just sends it via the latest one. Can this even be done?

    Read the article

  • What programming technique not done by you, was ahead of its time?

    - by Ferds
    There are developers who understand a technology and produce a solution months or years ahead of its time. I worked with a guy who designed an system using C# beta which would monitor different system components on several servers. He used SQL Server that would pick up these system monitoring components (via reflection) and would instantiate them via an NT Service. The simplicity in this design, was that another developer (me), who understood part of a system, would produce a component that could monitor it, as he had the specialized knowledge of that part of the system. I would derive from the monitor base class (to start, stop and log info), install on the monitoring server GAC and then add an entry to the components table in sql server. Then the main engine would pick up this component and do its magic. I understood parts of it, but couldn't work out by derive from a base class, why add to the GAC etc. This was 6 years ago and it took me months to realize what he achieved. What programming technique not done by you was ahead of its time? EDIT : Techniques that you have seen at work or journals/blogs - I don't mean historically over years.

    Read the article

  • Resize my image on upload not working - what must my buffer be?

    - by Etienne
    This is the code i got from This Link I want the user to upload a picture and then resize it............. Public Sub ResizeFromStream(ByVal ImageSavePath As String, ByVal MaxSideSize As Integer, ByVal Buffer As System.IO.Stream) Dim intNewWidth As Integer Dim intNewHeight As Integer Dim imgInput As System.Drawing.Image = System.Drawing.Image.FromStream(Buffer) 'Determine image format Dim fmtImageFormat As ImageFormat = imgInput.RawFormat 'get image original width and height Dim intOldWidth As Integer = imgInput.Width Dim intOldHeight As Integer = imgInput.Height 'determine if landscape or portrait Dim intMaxSide As Integer If (intOldWidth >= intOldHeight) Then intMaxSide = intOldWidth Else intMaxSide = intOldHeight End If If (intMaxSide > MaxSideSize) Then 'set new width and height Dim dblCoef As Double = MaxSideSize / CDbl(intMaxSide) intNewWidth = Convert.ToInt32(dblCoef * intOldWidth) intNewHeight = Convert.ToInt32(dblCoef * intOldHeight) Else intNewWidth = intOldWidth intNewHeight = intOldHeight End If 'create new bitmap Dim bmpResized As Drawing.Bitmap = New Drawing.Bitmap(imgInput, intNewWidth, intNewHeight) 'save bitmap to disk bmpResized.Save(ImageSavePath, fmtImageFormat) 'release used resources imgInput.Dispose() bmpResized.Dispose() Buffer.Close() End Sub Now when i click on my submit button it must execute my code but i am not sure what the input must be for the Buffer field? Protected Sub btnUpload_Click() Handles btnUpload.Click ResizeFromStream("~Pics", 200, ??????????) End Sub Thanks in advanced! Edit I need to get my Image from the File Upload control!

    Read the article

  • mysql get table based on common column between two tables

    - by Zentdayn
    while trying to learn sql i came across "Learn SQL The Hard Way" and i started reading it. Everything was going fine then i thought ,as a way to practice, to make something like given example in the book (example consists in 3 tables pet,person,person_pet and the person_pet table 'links' pets to their owners). I made this: report table +----+-------------+ | id | content | +----+-------------+ | 1 | bank robbery| | 2 | invalid | | 3 | cat on tree | +----+-------------+ notes table +-----------+--------------------+ | report_id | content | +-----------+--------------------+ | 1 | they had guns | | 3 | cat was saved | +-----------+--------------------+ wanted result +-----------+--------------------+---------------+ | report_id | report_content | report_notes | +-----------+--------------------+---------------+ | 1 | bank robbery | they had guns | | 2 | invalid | null or '' | | 3 | cat on tree | cat was saved | +-----------+--------------------+---------------+ I tried a few combinations but no success. My first thought was SELECT report.id,report.content AS report_content,note.content AS note_content FROM report,note WHERE report.id = note.report_id but this only returns the ones that have a match (would not return the invalid report). after this i tried adding IF conditions but i just made it worse. My question is, is this something i will figure out after getting past basic sql or can this be done in simple way? Anyway i would appreciate any help, i pretty much lost with this. Thank you. EDIT: i have looked into related questions but havent yet found one that solves my problem. I probably need to look into other statements such as join or something to sort this out.

    Read the article

< Previous Page | 625 626 627 628 629 630 631 632 633 634 635 636  | Next Page >