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  • Using Objective-C Blocks

    - by Sean
    Today I was experimenting with Objective-C's blocks so I thought I'd be clever and add to NSArray a few functional-style collection methods that I've seen in other languages: @interface NSArray (FunWithBlocks) - (NSArray *)collect:(id (^)(id obj))block; - (NSArray *)select:(BOOL (^)(id obj))block; - (NSArray *)flattenedArray; @end The collect: method takes a block which is called for each item in the array and expected to return the results of some operation using that item. The result is the collection of all of those results. (If the block returns nil, nothing is added to the result set.) The select: method will return a new array with only the items from the original that, when passed as an argument to the block, the block returned YES. And finally, the flattenedArray method iterates over the array's items. If an item is an array, it recursively calls flattenedArray on it and adds the results to the result set. If the item isn't an array, it adds the item to the result set. The result set is returned when everything is finished. So now that I had some infrastructure, I needed a test case. I decided to find all package files in the system's application directories. This is what I came up with: NSArray *packagePaths = [[[NSSearchPathForDirectoriesInDomains(NSAllApplicationsDirectory, NSAllDomainsMask, YES) collect:^(id path) { return (id)[[[NSFileManager defaultManager] contentsOfDirectoryAtPath:path error:nil] collect:^(id file) { return (id)[path stringByAppendingPathComponent:file]; }]; }] flattenedArray] select:^(id fullPath) { return [[NSWorkspace sharedWorkspace] isFilePackageAtPath:fullPath]; }]; Yep - that's all one line and it's horrid. I tried a few approaches at adding newlines and indentation to try to clean it up, but it still feels like the actual algorithm is lost in all the noise. I don't know if it's just a syntax thing or my relative in-experience with using a functional style that's the problem, though. For comparison, I decided to do it "the old fashioned way" and just use loops: NSMutableArray *packagePaths = [NSMutableArray new]; for (NSString *searchPath in NSSearchPathForDirectoriesInDomains(NSAllApplicationsDirectory, NSAllDomainsMask, YES)) { for (NSString *file in [[NSFileManager defaultManager] contentsOfDirectoryAtPath:searchPath error:nil]) { NSString *packagePath = [searchPath stringByAppendingPathComponent:file]; if ([[NSWorkspace sharedWorkspace] isFilePackageAtPath:packagePath]) { [packagePaths addObject:packagePath]; } } } IMO this version was easier to write and is more readable to boot. I suppose it's possible this was somehow a bad example, but it seems like a legitimate way to use blocks to me. (Am I wrong?) Am I missing something about how to write or structure Objective-C code with blocks that would clean this up and make it clearer than (or even just as clear as) the looped version?

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  • Hex colors: Numeric representation for "transparent"?

    - by Pekka
    I am building a web CMS in which the user can choose colours for certain site elements. I would like to convert all colour values to hex to avoid any further formatting hassle ("rgb(x,y,z)" or named colours). I have found a good JS library for that. The only thing that I can't get into hex is "transparent". I need this when explicitly declaring an element as transparent, which in my experience can be different from not defining any value at all. Does anybody know whether this can be turned into some numeric form? Will I have to set up all processing instances to accept hex values or "transparent"? I can't think of any other way.

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  • Lisp Style question label local functions or not?

    - by Andrew Myers
    I was wondering if there is a standard practice regarding the use of labels in Lisp. I've been messing around with a Lisp implementation of the algorithm described in the first answer here http://stackoverflow.com/questions/352203/generating-permutations-lazily My current version uses labels to break out portions of functionality. (defun next-permutation (pmute) (declare (vector pmute)) (let ((len (length pmute))) (if (> len 2) (labels ((get-pivot () (do ((pivot (1- len) (1- pivot))) ((or (= pivot 0) (< (aref pmute (1- pivot)) (aref pmute pivot))) pivot))) (get-swap (pivot) (let ((swp (1- len))) (loop for i from (1- len) downto pivot do (if (or (and (> (aref pmute i) (aref pmute (1- pivot))) (< (aref pmute i) (aref pmute swp))) (< (aref pmute swp) (aref pmute (1- pivot)))) (setf swp i))) swp)) (next (swp pivot) (rotatef (aref pmute (1- pivot)) (aref pmute swp)) (reverse-vector pmute pivot (1- len)))) (let ((piv (get-pivot))) (if (> piv 0) (next (get-swap piv) piv) nil)))))) Since each label is only called once I was wondering if this is considered bad practice since the only reason to do it in this case is for aesthetic reasons. I would argue that the current version with labels is clearer but that may go against common wisdom that I'm not aware of, being new to Lisp.

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  • Change the contrast of Image like Adobe Photoshop in ASP.net C#

    - by Hoque
    While I was trying to change the brightness and contrast of Image using C#, but I could not get success in changing the contrast of the Image. May I expect any support from here. I am using ColorMatrix to do that. Here are the code that I am using for brightness(works fine) and contrast(does not work properly). public static ColorMatrix CreateBrightnessMatrix(float Brightness) { if (Brightness < -1 || Brightness > 1) throw new ArgumentOutOfRangeException("Brightness value is out of range"); ColorMatrix cm = new ColorMatrix(new float[][]{ new float[] { 1f, 0, 0, 0, 0}, new float[] { 0, 1f, 0, 0, 0}, new float[] { 0, 0, 1f, 0, 0}, new float[] { 0, 0, 0, 1f, 0}, new float[] {Brightness, Brightness, Brightness, 1f, 1f}}); return cm; } public static ColorMatrix CreateContrastMatrix(float Contrast) { if (Contrast < 0 || Contrast > 3) throw new ArgumentOutOfRangeException("Contrast value is out of range"); float Trans = (1f - Contrast) / 2f; ColorMatrix cm = new ColorMatrix(new float[][]{ new float[] {Contrast, 0f, 0f, 0f, 0f}, new float[] { 0f, Contrast, 0f, 0f, 0f}, new float[] { 0f, 0f, Contrast, 0f, 0f}, new float[] { 0f, 0f, 0f, 1f, 0f}, new float[] { Trans, Trans, Trans, 0f, 1f}}); return cm; } Thanks.

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  • Objective-C RGB to HSB

    - by Johannes Jensen
    Let's say I've got the colour FF0000, which is red. Finding a darker colour is easy, I just type maybe CC instead of the FF, but let's say I've got the colour AE83FC, which is a complicated colour, how the heck would I find a lighter or darker version of it automatically? I figured the easy way to do this is to convert my RGB to HSB [Hue, Saturation, Brightness] How would I do that in Objective-C? Let's say I've got a RGB which is: 1.0, 0.0, 0.0. That's red. CGFloat r = 1.0; CGFloat g = 0.0; CGfloat b = 0.0; How would I convert that to HSB and then transform the colors and make it go back to RGB to I can use CGContextRGBSetFillColor? Are there any HSB functions? Please help. :)

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  • Are endless loops in bad form?

    - by rlbond
    So I have some C++ code for back-tracking nodes in a BFS algorithm. It looks a little like this: typedef std::map<int> MapType; bool IsValuePresent(const MapType& myMap, int beginVal, int searchVal) { int current_val = beginVal; while (true) { if (current_val == searchVal) return true; MapType::iterator it = myMap.find(current_val); assert(current_val != myMap.end()); if (current_val == it->second) // end of the line return false; current_val = it->second; } } However, the while (true) seems... suspicious to me. I know this code works, and logically I know it should work. However, I can't shake the feeling that there should be some condition in the while, but really the only possible one is to use a bool variable just to say if it's done. Should I stop worrying? Or is this really bad form. EDIT: Thanks to all for noticing that there is a way to get around this. However, I would still like to know if there are other valid cases.

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  • When should I use Perl's AUTOLOAD?

    - by Robert S. Barnes
    In "Perl Best Practices" the very first line in the section on AUTOLOAD is: Don't use AUTOLOAD However all the cases he describes are dealing with OO or Modules. I have a stand alone script in which some command line switches control which versions of particular functions get defined. Now I know I could just take the conditionals and the evals and stick them naked at the top of my file before everything else, but I find it convenient and cleaner to put them in AUTOLOAD at the end of the file. Is this bad practice / style? If you think so why, and is there a another way to do it? As per brian's request I'm basically using this to do conditional compilation based on command line switches. I don't mind some constructive criticism. sub AUTOLOAD { our $AUTOLOAD; (my $method = $AUTOLOAD) =~ s/.*:://s; # remove package name if ($method eq 'tcpdump' && $tcpdump) { eval q( sub tcpdump { my $msg = shift; warn gf_time()." Thread ".threads->tid().": $msg\n"; } ); } elsif ($method eq 'loginfo' && $debug) { eval q( sub loginfo { my $msg = shift; $msg =~ s/$CRLF/\n/g; print gf_time()." Thread ".threads->tid().": $msg\n"; } ); } elsif ($method eq 'build_get') { if ($pipelining) { eval q( sub build_get { my $url = shift; my $base = shift; $url = "http://".$url unless $url =~ /^http/; return "GET $url HTTP/1.1${CRLF}Host: $base$CRLF$CRLF"; } ); } else { eval q( sub build_get { my $url = shift; my $base = shift; $url = "http://".$url unless $url =~ /^http/; return "GET $url HTTP/1.1${CRLF}Host: $base${CRLF}Connection: close$CRLF$CRLF"; } ); } } elsif ($method eq 'grow') { eval q{ require Convert::Scalar qw(grow); }; if ($@) { eval q( sub grow {} ); } goto &$method; } else { eval "sub $method {}"; return; } die $@ if $@; goto &$method; }

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  • How to use Python list comprehension (or such) for retrieving rows when using MySQLdb?

    - by Erik Nygren
    Hey all, I use MySQLdb a lot when dealing with my webserver. I often find myself repeating the lines: row = cursor.fetchone() while row: do_processing(row) row = cursor.fetchone() Somehow this strikes me as somewhat un-pythonic. Is there a better, one-line way to accomplish the same thing, along the lines of inline assignment in C: while (row = do_fetch()) { do_processing(row); } I've tried figuring out the syntax using list comprehensions, but I can't seem to figure it out. Any recommendations? Thanks, Erik

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  • What is the C# static fields naming convention?

    - by Matt
    I have recently started using ReSharper which is a fantastic tool. Today I came across a naming rule for static fields, namely prefixing with an underscore ie. private static string _myString; Is this really the standard way to name static variables? If so is it just personal preference and style, or does it have some sort of lower level impact? Eg Compilation JIT etc? Where does this style originate from? I have always associated it with C++, is that correct?

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  • Can I apply a texture to UIToolbar?

    - by Ben
    I tried doing this: [toolbar setTint:[UIColor colorWithPatternImage:[UIImage imageNamed:@"thingFromMyBundle.png"]]]; but it just ended up black. At first I assumed you weren't allowed to "tint" with a texture, but I've seen apps recently that can do this. Am I missing something? Thanks.

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  • indentation preference and personality

    - by dreftymac
    This question is similar in spirit to : http://stackoverflow.com/questions/492178/links-between-personality-types-and-language-technology-preferences But it is based specifically on indentation (spaces vs tabs and the number of spaces). The reason I am asking here instead of searching is because I remember seeing a specific document writing about this. If I remember correctly, it also talked about why Linus prefers eight spaces.

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  • Is this good C# style?

    - by burnt1ce
    Consider the following method signature: public static bool TryGetPolls(out List<Poll> polls, out string errorMessage) This method performs the following: accesses the database to generate a list of Poll objects. returns true if it was success and errorMessage will be an empty string returns false if it was not successful and errorMessage will contain an exception message. Is this good style? Update: Lets say i do use the following method signature: public static List<Poll> GetPolls() and in that method, it doesn't catch any exceptions (so i depend the caller to catch exceptions). How do i dispose and close all the objects that is in the scope of that method? As soon as an exception is thrown, the code that closes and disposes objects in the method is no longer reachable.

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  • Style: Dot notation vs. message notation in Objective-C 2.0

    - by groundhog
    In Objective-C 2.0 we got the "dot" notation for properties. I've seen various back and forths about the merits of dot notation vs. message notation. To keep the responses untainted I'm not going to respond either way in the question. What is your thought about dot notation vs. message notation for property accessing? Please try to keep it focused on Objective-C - my one bias I'll put forth is that Objective-C is Objective-C, so your preference that it be like Java or JavaScript aren't valid. Valid commentary is to do with technical issues (operation ordering, cast precedence, performance, etc), clarity (structure vs. object nature, both pro and con!), succinctness, etc. Note, I'm of the school of rigorous quality and readability in code having worked on huge projects where code convention and quality is paramount (the write once read a thousand times paradigm).

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  • Visual Studio 2010 code display colour scheme - where do I find some properties?

    - by truthseeker
    I'm working on my own colour scheme for displaying code in visual studio. I can't find some text section name so I don't know where to change it's colour. :( Can anybody help me and tell me where do I find them, I mean what is the name of the following sections: 1)The grey one (documentation tag value and it's quote) - picture below 2)The olive colour: header of a asp.net in vb language document. - <% and underline. (picture below) *Here is second hyperlink but without the begining regarding this supid forum rules. To write my code I use vb.net language.

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  • How to convert RGB to BGR?

    - by Adam
    This is probably easy, but I'm trying to convert from a source which provides colors in RGB strings to an output in BGR strings in Java. I've been busting my brain and time on shifting and Long.decode and Long.toHexString. Feel free to also throw alpha values in there (RGBA - ABGR), though I think I can extend the principles.

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  • Override colorscheme

    - by RymdPung
    I often find myself wanting to change just something little in a colorscheme, but i don't want to edit the original file. I tried putting my change in '~/.vim/after/colors/blah.vim', but that doesn't work for me. Example, I want to change the CursorLine highlight in BusyBee.vim.. ~/.vim/colors/BusyBee.vim I create the file '~/.vim/after/colors/BusyBee.vim' and add this: hi CursorLine guibg=#000000 ctermbg=Black cterm=none However, i don't see the change. Of course it works if i change the line in the originial BusyBee.vim, but like i said i'd prefer not to do that. Doing... :colo Busy<TAB> Shows me... BusyBee BusyBee

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  • How do I code a green button in UIActionSheet?

    - by Joshua
    I am using the code: { randomstatus=0; msg=[[NSString alloc]initWithFormat:@"Good job, do you want to continue?"]; UIActionSheet *actionSheet=[[UIActionSheet alloc]initWithTitle:msg delegate:self cancelButtonTitle:@"No" destructiveButtonTitle:@"Yes" otherButtonTitles:nil]; [actionSheet showInView:self.view]; [actionSheet release]; [msg release]; } I don't want to change the code, but I need the "destructiveButton" to be green instead of red. Is this possible, or do i need to use a different button?

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  • Should all public methods of an API be documented?

    - by cynicalman
    When writing "library" type classes, is it better practice to always write markup documentation (i.e. javadoc) in java or assume that the code can be "self-documenting"? For example, given the following method stub: /** * Copies all readable bytes from the provided input stream to the provided output * stream. The output stream will be flushed, but neither stream will be closed. * * @param inStream an InputStream from which to read bytes. * @param outStream an OutputStream to which to copy the read bytes. * @throws IOException if there are any errors reading or writing. */ public void copyStream(InputStream inStream, OutputStream outStream) throws IOException { // copy the stream } The javadoc seems to be self-evident, and noise that just needs to be updated if the funcion is changed at all. But the sentence about flushing and not closing the stream could be valuable. So, when writing a library, is it best to: a) always document b) document anything that isn't obvious c) never document (code should speak for itself!) I usually use b), myself (since the code can be self-documenting otherwise)...

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