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  • Basic problems (type inference or something else?) in Objective-C/Cocoa.

    - by Matt
    Hi, Apologies for how basic these questions are to some. Just started learning Cocoa, working through Hillegass' book, and am trying to write my first program (a GUI Cocoa app that counts the number of characters in a string). I tried this: NSString *string = [textField stringValue]; NSUInteger *stringLength = [string length]; NSString *countString = (@"There are %u characters",stringLength); [label setStringValue:countString]; But I'm getting errors like: Incompatible pointer conversion initializing 'NSUInteger' (aka 'unsigned long'), expected 'NSUInteger *'[-pedantic] for the first line, and this for the second line: Incompatible pointer types initializing 'NSUInteger *', expected 'NSString *' [-pedantic] I did try this first, but it didn't work either: [label setStringValue:[NSString stringWithFormat:@"There are %u characters",[[textField stringValue] length]]] On a similar note, I've only written in easy scripting languages before now, and I'm not sure when I should be allocing/initing objects and when I shouldn't. For example, when is it okay to do this: NSString *myString = @"foo"; or int *length = 5; instead of this: NSString *myString = [[NSString alloc] initWithString:"foo"]; And which ones should I be putting into the header files? I did check Apple's documentation, and CocoaDev, and the book I'm working for but without luck. Maybe I'm looking in the wrong places.. Thanks to anyone who takes the time to reply this: it's appreciated, and thanks for being patient with a beginner. We all start somewhere. EDIT Okay, I tried the following again: [label setStringValue:[NSString stringWithFormat:@"There are %u characters",[[textField stringValue] length]]] And it actually worked this time. Not sure why it didn't the first time, though I think I might have typed %d instead of %u by mistake. However I still don't understand why the code I posted at the top of my original post doesn't work, and I have no idea what the errors mean, and I'd very much like to know because it seems like I'm missing something important there.

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  • JavaScript Intellisense Improvements with VS 2010

    - by ScottGu
    This is the twentieth in a series of blog posts I’m doing on the upcoming VS 2010 and .NET 4 release.  Today’s blog post covers some of the nice improvements coming with JavaScript intellisense with VS 2010 and the free Visual Web Developer 2010 Express.  You’ll find with VS 2010 that JavaScript Intellisense loads much faster for large script files and with large libraries, and that it now provides statement completion support for more advanced scenarios compared to previous versions of Visual Studio. [In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu] Improved JavaScript Intellisense Providing Intellisense for a dynamic language like JavaScript is more involved than doing so with a statically typed language like VB or C#.  Correctly inferring the shape and structure of variables, methods, etc is pretty much impossible without pseudo-executing the actual code itself – since JavaScript as a language is flexible enough to dynamically modify and morph these things at runtime.  VS 2010’s JavaScript code editor now has the smarts to perform this type of pseudo-code execution as you type – which is how its intellisense completion is kept accurate and complete.  Below is a simple walkthrough that shows off how rich and flexible it is with the final release. Scenario 1: Basic Type Inference When you declare a variable in JavaScript you do not have to declare its type.  Instead, the type of the variable is based on the value assigned to it.  Because VS 2010 pseudo-executes the code within the editor, it can dynamically infer the type of a variable, and provide the appropriate code intellisense based on the value assigned to a variable. For example, notice below how VS 2010 provides statement completion for a string (because we assigned a string to the “foo” variable): If we later assign a numeric value to “foo” the statement completion (after this assignment) automatically changes to provide intellisense for a number: Scenario 2: Intellisense When Manipulating Browser Objects It is pretty common with JavaScript to manipulate the DOM of a page, as well as work against browser objects available on the client.  Previous versions of Visual Studio would provide JavaScript statement completion against the standard browser objects – but didn’t provide much help with more advanced scenarios (like creating dynamic variables and methods).  VS 2010’s pseudo-execution of code within the editor now allows us to provide rich intellisense for a much broader set of scenarios. For example, below we are using the browser’s window object to create a global variable named “bar”.  Notice how we can now get intellisense (with correct type inference for a string) with VS 2010 when we later try and use it: When we assign the “bar” variable as a number (instead of as a string) the VS 2010 intellisense engine correctly infers its type and modifies statement completion appropriately to be that of a number instead: Scenario 3: Showing Off Because VS 2010 is psudo-executing code within the editor, it is able to handle a bunch of scenarios (both practical and wacky) that you throw at it – and is still able to provide accurate type inference and intellisense. For example, below we are using a for-loop and the browser’s window object to dynamically create and name multiple dynamic variables (bar1, bar2, bar3…bar9).  Notice how the editor’s intellisense engine identifies and provides statement completion for them: Because variables added via the browser’s window object are also global variables – they also now show up in the global variable intellisense drop-down as well: Better yet – type inference is still fully supported.  So if we assign a string to a dynamically named variable we will get type inference for a string.  If we assign a number we’ll get type inference for a number.  Just for fun (and to show off!) we could adjust our for-loop to assign a string for even numbered variables (bar2, bar4, bar6, etc) and assign a number for odd numbered variables (bar1, bar3, bar5, etc): Notice above how we get statement completion for a string for the “bar2” variable.  Notice below how for “bar1” we get statement completion for a number:   This isn’t just a cool pet trick While the above example is a bit contrived, the approach of dynamically creating variables, methods and event handlers on the fly is pretty common with many Javascript libraries.  Many of the more popular libraries use these techniques to keep the size of script library downloads as small as possible.  VS 2010’s support for parsing and pseudo-executing libraries that use these techniques ensures that you get better code Intellisense out of the box when programming against them. Summary Visual Studio 2010 (and the free Visual Web Developer 2010 Express) now provide much richer JavaScript intellisense support.  This support works with pretty much all popular JavaScript libraries.  It should help provide a much better development experience when coding client-side JavaScript and enabling AJAX scenarios within your ASP.NET applications. Hope this helps, Scott P.S. You can read my previous blog post on VS 2008’s JavaScript Intellisense to learn more about our previous JavaScript intellisense (and some of the scenarios it supported).  VS 2010 obviously supports all of the scenarios previously enabled with VS 2008.

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  • JDK 7 In Action - Learn With Java Tutorials and Developer Guides

    - by sowmya
    At JavaOne 2012, Stuart Marks, Mike Duigou, and Joe Darcy gave a presentation about JDK 7 In Action. Learn more about using JDK 7 features with the help of Java Tutorials and JDK 7 Developer Guides. Links to relevant information are provided below. If you are considering moving to JDK 7 from a previous release, the JDK 7 Release Notes and JDK 7 Adoption Guide are great resources. Project Coin Features Improved Literals * Literals section in Primitive Datatypes topic. * Binary Literals * Underscores in Numeric Literals Strings In Switch * Strings In Switch Diamond * Type Inference for Generic Instance Creation * Type Inference and Instantiation of Generic Classes Multi-catch and Precise Throw * Catching Multiple Exception Types and Rethrowing Exceptions with Improved Type Checking * Catch Blocks Try-with-resources * The try-with-resources Statement NIO.2 File System API * File I/O for information on path, files, change notification, and more * Zip File System Provider * Zip File System Provider * Developing a Custom File System Provider Fork Join Framework * Fork/Join - Sowmya

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  • Why doesn't Haskell have type-level lambda abstractions?

    - by Petr Pudlák
    Are there some theoretical reasons for that (like that the type checking or type inference would become undecidable), or practical reasons (too difficult to implement properly)? Currently, we can wrap things into newtype like newtype Pair a = Pair (a, a) and then have Pair :: * -> * but we cannot do something like ?(a:*). (a,a). (There are some languages that have them, for example, Scala does.)

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  • Developer Notebook i5 or i7

    - by Cas Sakal
    I could not decide on which configuration below gives better performance for developers on a notebook(running VS.NET, SQL Server, no gaming); (A) i5 540M + SSD (Intel) or (B) i7 720M + 7200 RPM HDD (Western Digital) Since these two configurations(A, B) costs nearly same $ for me, I would like to buy the fastest one for my job environment. Please do not comment just buy this or that, if you can give an inference about your choice I would be appreciated. Thank you, cas

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  • What's the difference between Scala and Red Hat's Ceylon language?

    - by John Bryant
    Red Hat's Ceylon language has some interesting improvements over Java: The overall vision: learn from Java's mistakes, keep the good, ditch the bad The focus on readability and ease of learning/use Static Typing (find errors at compile time, not run time) No “special” types, everything is an object Named and Optional parameters (C# 4.0) Nullable types (C# 2.0) No need for explicit getter/setters until you are ready for them (C# 3.0) Type inference via the "local" keyword (C# 3.0 "var") Sequences (arrays) and their accompanying syntactic sugariness (C# 3.0) Straight-forward implementation of higher-order functions I don't know Scala but have heard it offers some similar advantages over Java. How would Scala compare to Ceylon in this respect?

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  • What is the supposed productivity gain of dynamic typing?

    - by hstoerr
    I often heard the claim that dynamically typed languages are more productive than statically typed languages. What are the reasons for this claim? Isn't it just tooling with modern concepts like convention over configuration, the use of functional programming, advanced programming models and use of consistent abstractions? Admittedly there is less clutter because the (for instance in Java) often redundant type declarations are not needed, but you can also omit most type declarations in statically typed languages that usw type inference, without loosing the other advantages of static typing. And all of this is available for modern statically typed languages like Scala as well. So: what is there to say for productivity with dynamic typing that really is an advantage of the type model itself?

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  • Variable declaration versus assignment syntax

    - by rwallace
    Working on a statically typed language with type inference and streamlined syntax, and need to make final decision about syntax for variable declaration versus assignment. Specifically I'm trying to choose between: // Option 1. Create new local variable with :=, assign with = foo := 1 foo = 2 // Option 2. Create new local variable with =, assign with := foo = 1 foo := 2 Creating functions will use = regardless: // Indentation delimits blocks square x = x * x And assignment to compound objects will do likewise: sky.color = blue a[i] = 0 Which of options 1 or 2 would people find most convenient/least surprising/otherwise best?

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  • Worst practices in C++, common mistakes ...

    - by Felix Dombek
    After reading this famous rant by Linus Torvalds, I wondered what actually are all the bad things programmers might do in C++. I'm explicitly not referring to typography errors or bad program flow as treated in this question and answers, but to more high-level errors which are not detected by the compiler and do not result in obvious bugs at first run, complete design errors, things which are improbable in C but are likely to be done by newcomers who don't understand the full implications of their code. I also welcome answers pointing out a huge performance decrease where it would not usually be expected. An example of what one of my professors once told me: You have used somewhat too many instances of unneeded inheritance and virtuality. Inheritance makes a design much more complicated (and inefficient because of the RTTI (run-time type inference) subsystem), and it should therefore only be used where it makes sense, e.g. for the actions in the parse table." [I wrote an LR(1) parser generator.] "Because you make intensive use of templates, you practically don't need inheritance."

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  • problem with a join

    - by Luca Romagnoli
    I have this code: int se = (int) settings.GruppoSegreteria; var acc = db.USR_Accounts.Where( p => p.ID_Gruppo == se); var segreterie = from s in db.USR_Utenti join h in acc on s.ID equals h.USR_UtentiReference select s; And this error: The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'Join' I don't understand it. Can you help me? thanks

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  • Scala return type for tuple-functions

    - by Felix
    Hello Guys, I want to make a scala function which returns a scala tuple. I can do a function like this: def foo = (1,"hello","world") and this will work fine, but now I want to tell the compiler what I expect to be returned from the function instead of using the built in type inference (after all, I have no idea what a (1,"hello","world") is) I thought I remembered the classname being something like Tuple3[Int,String,String] but that doesnt work for me. Suggestions? :D (ps: I love stack overflow!)

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  • Type hinting for functions in Clojure

    - by mikera
    I'm trying to resolve a reflection warning in Clojure that seems to result from the lack of type inference on function return values that are normal Java objects. Trivial example code that demonstrates the issue: (set! *warn-on-reflection* true) (defn foo [#^Integer x] (+ 3 x)) (.equals (foo 2) (foo 2)) => Reflection warning, NO_SOURCE_PATH:10 - call to equals can't be resolved. true What is the best way to solve this? Can this be done with type hints?

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  • error with linq join

    - by Luca Romagnoli
    I have this linq query: var segreterie = from s in db.USR_Utenti join h in db.USR_Accounts on new {s.ID, settings.GruppoSegreteria} equals new {h.USR_UtentiReference,h.ID_Gruppo} select s; that has this problem: The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'Join'. how can i do to solve it?

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  • Better Performance with Laptop i5+SSD or i7+HDD [closed]

    - by Cas Sakal
    Possible Duplicates: i5 vs. i7 processor dev laptop Developer Notebook i5 or i7 I could not decide on which configuration below gives better performance for developers on a notebook(running VS.NET, SQL Server, no gaming); (A) i5 540M + SSD (Intel) or (B) i7 720M + 7200 RPM HDD (Western Digital) Since these two configurations(A, B) costs nearly same $ for me, I would like to buy the fastest one for my job environment. Please do not comment just buy this or that, if you can give an inference about your choice I would be appreciated. Thank you, cas

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  • Type of AI to tackle this problem?

    - by user1154277
    I posted this on stackoverflow but want to get your recommendations as well as a user on overflow recommended I post it here. I'm going to say from the beginning that I am not a programmer, I have a cursory knowledge of different types of AI and am just a businessman building a web app. Anyways, the web app I am investing in to develop is for a hobby of mine. There are many part manufacturers, product manufacturers, upgrade and addon manufacturers etc. for hardware/products in this hobby's industry. Currently, I am in the process of building a crowd sourced platform for people who are knowledgeable to go in and mark up compatibility between those parts as its not always clear cut if they are for example: Manufacturer A makes a "A" class product, and manufacturer B makes upgrade/part that generally goes with class "A" products, but is for one reason or another not compatible with Manufacturer A's particular "A" class product. However, a good chunk (60%-70%) of the products/parts in the database can have their compatibility inferenced by their properties, For example: Part 1 is type "A" with "X" mm receiver and part 2 is also Type "A" with "X" mm interface and thus the two parts are compatible.. or Part 1 is a 8mm gear, thus all bushings of 8mm from any manufacturer is compatible with part 1. Further more, all gears can only have compatibility relationships in the database with bushing and gear boxes, but there can be no meaningful compatibility between a gear and a rail, or receiver since those parts don't interface. Now what I want is an AI to be able to learn from the decisions of the crowdsourced platform community and be able to inference compatibility for new parts/products based on their tagged attributes, what type of part they are etc. What would be the best form of AI to tackle this? I was thinking a Expert System, but explicitly engineering all of the knowledge rules would be daunting because of the complex relations between literally tens of thousands of parts, hundreds of part types and many manufacturers. Would a ANN (neural network) be ideal to learn from the many inputs/decisions of the crowdsource platform users? Any help/input is much appreciated.

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  • nmake makefile, linking objects files in a subfolder

    - by Gauthier
    My makefile defines a link command: prod_link = $(LINK) $(LINK_FLAGS) -o$(PROD_OUT) $(PROD_OBJS) where $(PROD_OBJS) is a list of object files of the form: PROD_OBJS = objfile1.obj objfile2.obj objfile3.obj ... objfileN.obj Now the makefile itself is at the root of my project directory. It gets messy to have object and listing files at the root, I'd like to put them in a subfolder. Building and outputing the obj files to a subfolder works, I'm doing it with suffixes and inference: .s.obj: $(ASSEMBLY) $(FLAGS) $*.s -o Objects\$*.obj The problem is to pass the Objects folder to the link command. I tried: prod_link = $(LINK) $(LINK_FLAGS) -o$(PROD_OUT) Objects\$(PROD_OBJS) but only the first file in the list of object files gets the folder's name. How can I pass the Objects subfolder to all files of my list $(PROD_OBJS)? EDIT I tried also PROD_OBJS = $(patsubst %.ss,Object\%.obj, $(PROD_SRC)) but got: makefile(51) : fatal error U1000: syntax error : ')' missing in macro invocation Stop. This is quite strange...

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  • Ending a Rails 2 URL with an IP address causes routing error?

    - by Dave Williams
    I'm trying to construct URLs in the format http://servername/find/by/CRITERION/VALUE CRITERION is a finite set of strings, as is VALUE. Trouble is, VALUE needs to be an IP address in some situations, and it's causing me a routing error. Here's my route: map.find 'find/by/:criterion/:query', :controller => "find", :action => "by" And the error, from the Mongrel logs: Processing ApplicationController#index (for 127.0.0.1 at 2010-05-07 10:20:32) [GET] ActionController::RoutingError (No route matches "/find/by/ip/1.2.3.4" with {:method=>:get}): Rendering rescues/layout (not_found) If I visit /find/by/foo/bar or /find/by/foo/1234 I don't have problems. I suspect the problem might be Rails' inference of MIME types based on periods in the URL, but I don't really know how I can disable that. I've tried passing a :defaults = {:format = :html} to the route but that causes Mongrel to fail to start entirely. Any help appreciated!

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  • f# naming conventions.. WTF??!!

    - by Peter Goras
    let w t f = have I missed something? do all value names in F# have to be a single char? preferably x? and do all method names have to abbreviated to a cryptic four chars?? we've had it rammed down our throats for years about descriptive variable/method names in other languages but now this doesnt apply to F#? or it is some coding 'style' bollox? Learning from code examples is hard enough with type inference. why make it harder?

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  • Functional languages targeting the LLVM

    - by Matthew
    Are there any languages that target the LLVM that: Are statically typed Use type inference Are functional (i.e. lambda expressions, closures, list primitives, list comprehensions, etc.) Have first class object-oriented features (inheritance, polymorphism, mixins, etc.) Have a sophisticated type system (generics, covariance and contravariance, etc.) Scala is all of these, but only targets the JVM. F# (and to some extent C#) is most if not all of these, but only targets .NET. What similar language targets the LLVM?

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  • template function roundTo int, float -> truncation

    - by Oops
    Hi, according to this question: http://stackoverflow.com/questions/2833730/calling-template-function-without-type-inference the round function I will use in the future now looks like: template < typename TOut, typename TIn > TOut roundTo( TIn value ) { return static_cast<TOut>( value + 0.5 ); } double d = 1.54; int i = rountTo<int>(d); However it makes sense only if it will be used to round to integral datatypes like char, short, int, long, long long int, and it's unsigned counterparts. If it ever will be used with a TOut As float or long double it will deliver s***. double d = 1.54; float f = roundTo<float>(d); // aarrrgh now float is 2.04; I was thinking of a specified overload of the function but ... that's not possible... How would you solve this problem? many thanks in advance Oops

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  • Type signature "Maybe a" doesn't like "Just [Event]"

    - by sisif
    I'm still learning Haskell and need help with the type inference please! Using packages SDL and Yampa I get the following type signature from FRP.Yampa.reactimate: (Bool -> IO (DTime, Maybe a)) and I want to use it for: myInput :: Bool -> IO (DTime, Maybe [SDL.Event]) myInput isBlocking = do event <- SDL.pollEvent return (1, Just [event]) ... reactimate myInit myInput myOutput mySF but it says Couldn't match expected type `()' against inferred type `[SDL.Event]' Expected type: IO (DTime, Maybe ()) Inferred type: IO (DTime, Maybe [SDL.Event]) In the second argument of `reactimate', namely `input' In the expression: reactimate initialize input output process I thought Maybe a allows me to use anything, even a SDL.Event list? Why is it expecting Maybe () when the type signature is actually Maybe a? Why does it want an empty tuple, or a function taking no arguments, or what is () supposed to be?

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  • (newbie) type signature "Maybe a" doesn't like "Just [Event]"

    - by sisif
    i'm still learning Haskell and need help with the type inference please! using packages SDL and Yampa i get the following type signature from FRP.Yampa.reactimate: (Bool -> IO (DTime, Maybe a)) and i want to use it for: myInput :: Bool -> IO (DTime, Maybe [SDL.Event]) myInput isBlocking = do event <- SDL.pollEvent return (1, Just [event]) ... reactimate myInit myInput myOutput mySF but it says Couldn't match expected type `()' against inferred type `[SDL.Event]' Expected type: IO (DTime, Maybe ()) Inferred type: IO (DTime, Maybe [SDL.Event]) In the second argument of `reactimate', namely `input' In the expression: reactimate initialize input output process i thought "Maybe a" allows me to use anything, even a SDL.Event list? why is it expecting "Maybe ()" when the type signature is actually "Maybe a"? why does it want an empty tuple, or a function taking no arguments, or what is () supposed to be?

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  • Simple method for reliably detecting code in text?

    - by Jeff Atwood
    GMail has this feature where it will warn you if you try to send an email that it thinks might have an attachment. Because GMail detected the string see the attached in the email, but no actual attachment, it warns me with an OK / Cancel dialog when I click the Send button. We have a related problem on Stack Overflow. That is, when a user enters a post like this one: my problem is I need to change the database but I don't won't to create a new connection. example: DataSet dsMasterInfo = new DataSet(); Database db = DatabaseFactory.CreateDatabase("ConnectionString"); DbCommand dbCommand = db.GetStoredProcCommand("uspGetMasterName"); This user did not format their code as code! That is, they didn't indent by 4 spaces per Markdown, or use the code button (or the keyboard shortcut ctrl+k) which does that for them. Thus, our system is accreting a lot of edits where people have to go in and manually format code for people that are somehow unable to figure this out. This leads to a lot of bellyaching. We've improved the editor help several times, but short of driving over to the user's house and pressing the correct buttons on their keyboard for them, we're at a loss to see what to do next. That's why we are considering a Google GMail style warning: Did you mean to post code? You wrote stuff that we think looks like code, but you didn't format it as code by indenting 4 spaces, using the toolbar code button or the ctrl+k code formatting command. However, presenting this warning requires us to detect the presence of what we think is unformatted code in a question. What is a simple, semi-reliable way of doing this? Per Markdown, code is always indented by 4 spaces or within backticks, so anything correctly formatted can be discarded from the check immediately. This is only a warning and it will only apply to low-reputation users asking their first questions (or providing their first answers), so some false positives are OK, so long as they are about 5% or less. Questions on Stack Overflow can be in any language, though we can realistically limit our check to, say, the "big ten" languages. Per the tags page that would be C#, Java, PHP, JavaScript, Objective-C, C, C++, Python, Ruby. Use the Stack Overflow creative commons data dump to audit your potential solution (or just pick a few questions in the top 10 tags on Stack Overflow) and see how it does. Pseudocode is fine, but we use c# if you want to be extra friendly. The simpler the better (so long as it works). KISS! If your solution requires us to attempt to compile posts in 10 different compilers, or an army of people to manually train a bayesian inference engine, that's ... not exactly what we had in mind.

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