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  • Why no switch on pointers?

    - by meeselet
    For instance: #include <stdio.h> void why_cant_we_switch_him(void *ptr) { switch (ptr) { case NULL: printf("NULL!\n"); break; default: printf("%p!\n", ptr); break; } } int main(void) { void *foo = "toast"; why_cant_we_switch_him(foo); return 0; } gcc test.c -o test test.c: In function 'why_cant_we_switch_him': test.c:5: error: switch quantity not an integer test.c:6: error: pointers are not permitted as case values Just curious. Is this a technical limitation? EDIT People seem to think there is only one constant pointer expression. Is that is really true, though? For instance, here is a common paradigm in Objective-C (it is really only C aside from NSString, id and nil, which are merely a pointers, so it is still relevant — I just wanted to point out that there is, in fact, a common use for it, despite this being only a technical question): #include <stdio.h> #include <Foundation/Foundation.h> static NSString * const kMyConstantObject = @"Foo"; void why_cant_we_switch_him(id ptr) { switch (ptr) { case kMyConstantObject: // (Note that we are comparing pointers, not string values.) printf("We found him!\n"); break; case nil: printf("He appears to be nil (or NULL, whichever you prefer).\n"); break; default: printf("%p!\n", ptr); break; } } int main(void) { NSString *foo = @"toast"; why_cant_we_switch_him(foo); foo = kMyConstantObject; why_cant_we_switch_him(foo); return 0; } gcc test.c -o test -framework Foundation test.c: In function 'why_cant_we_switch_him': test.c:5: error: switch quantity not an integer test.c:6: error: pointers are not permitted as case values It appears that the reason is that switch only allows integral values (as the compiler warning said). So I suppose a better question would be to ask why this is the case? (though it is probably too late now.)

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  • Difficulty adding widgets to django form.

    - by codingJoe
    I have a django app that tracks activities that can benefit a classroom. Using the django examples, I was able to build a form to enter this data. But when I try to add widgets to that form, things get tricky. What I want is a calendar widget that lets the user enter the 'activity_date' field using a widget. If I use Admin interface. The AdminDateWidget works fine. however. This particular user isn't allowed access to the admin interface so I need a different way to present this widget. Also I couldn't figure out how to make the bring the admin widget over into non-admin pages. So I tried a custom widget. This is the first custom widget I've built, so I'm not quite sure what is supposed to be going on here. Any Expert Advice? How do I get my date widget to work? # The Model class Activity(models.Model): activity_date = models.DateField() activity_type = models.CharField(max_length=50, choices=ACTIVITY_TYPES) activity_description = models.CharField(max_length=200) activity_duration= models.DecimalField(decimal_places=2, max_digits=4) est_attendance = models.IntegerField("Estimated attendance") # The Form class ActivityForm(forms.ModelForm): # The following line causes lockup if enabled. # With the DateTimeWidget removed, the form functions correctly except that there is no widget. #activity_date = forms.DateField(label=_('Date'), widget=DateTimeWidget) ##!!! Point of Error !!! class Meta: model = Activity fields = ('activity_date', 'activity_type', 'activity_description', 'activity_duration', 'est_attendance') def __init__(self, *args, **kwargs): super(ActivityForm, self).__init__(*args, **kwargs) instance = getattr(self, 'instance', None) edit_aid = kwargs.get('edit_aid', False) # On a different approach, the following also didn't work. #self.fields['activity_date'].widget = widgets.AdminDateWidget() # The Widget # Example referenced: http://djangosnippets.org/snippets/391/ calbtn = u""" <button id="calendar-trigger">...</button> <img src="%s/site_media/images/icon_calendar.gif" alt="calendar" id="%s_btn" style="cursor: pointer; border: 1px solid #8888aa;" title="Select date and time" onmouseover="this.style.background='#444444';" onmouseout="this.style.background=''" /> <script type="text/javascript"> Calendar.setup({ trigger : "calendar-trigger", inputField : "%s" }); </script>""" class DateTimeWidget(forms.widgets.TextInput): dformat = '%Y-%m-%d %H:%M' def render(self, name, value, attrs=None): print "DTWgt render name=%s, value=%s" % name, value if value is None: value = '' final_attrs = self.build_attrs(attrs, type=self.input_type, name=name) if value != '': try: final_attrs['value'] = \ force_unicode(value.strftime(self.dformat)) except: final_attrs['value'] = \ force_unicode(value) if not final_attrs.has_key('id'): final_attrs['id'] = u'%s_id' % (name) id = final_attrs['id'] jsdformat = self.dformat #.replace('%', '%%') cal = calbtn % (settings.MEDIA_URL, id, id, jsdformat, id) a = u'<input%s />%s' % (forms.util.flatatt(final_attrs), cal) print "render return %s " % a return mark_safe(a) def value_from_datadict(self, data, files, name): print "DTWgt value_from_datadict" dtf = forms.fields.DEFAULT_DATETIME_INPUT_FORMATS empty_values = forms.fields.EMPTY_VALUES value = data.get(name, None) if value in empty_values: return None if isinstance(value, datetime.datetime): return value if isinstance(value, datetime.date): return datetime.datetime(value.year, value.month, value.day) for format in dtf: try: return datetime.datetime(*time.strptime(value, format)[:6]) except ValueError: continue return None

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  • Why is RSpec so slow under Rails?

    - by Adrian Dunston
    Whenever I run rspec tests for my Rails application it takes forever and a day of overhead before it actually starts running tests. Why is rspec so slow? Is there a way to speed up Rails' initial load or single out the part of my Rails app I need (e.g. ActiveRecord stuff only) so it doesn't load absolutely everything to run a few tests?

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  • ZipArchive memory problems on iPhone for large archive

    - by Mithin
    Hi, I am trying to compress multiple files into a single zip archive and I am running into low memory warning. Since the complete zip file is loaded into the memory I guess that's the problem. Is there a way by which I can manage the compression/decompression better using ZipArchive so that not all the data is in the memory at once? Thanks!

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  • JavaScript Loop and wait for function

    - by Fluidbyte
    I have a simple single-dimension array, let's say: fruits = ["apples","bananas","oranges","peaches","plums"]; I can loop thru with with $.each() function: $.each(fruits, function(index, fruit) { showFruit(fruit); }); but I'm calling to another function which I need to finish before moving on to the next item. So, if I have a function like this: function showFruit(fruit){ $.getScript('some/script.js',function(){ // Do stuff }) } What's the best way to make sure the previous fruit has been appended before moving on?

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  • Objective C: Which is changed, property or ivar?

    - by Wilhelmsen
    Worrying about duplicates but can not seem to find and answer I can understand in any of the other posts, I just have to ask: When I have in my .h: @interface SecondViewController : UIViewController{ NSString *changeName; } @property (readwrite, retain) NSString *changeName; then in my .m @synthesize changeName; -(IBAction)changeButton:(id)sender{ changeName = @"changed"; } Is it the synthesized property or the instance variable that get changed when I press "changeButton" ?

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  • Hibernate persist order

    - by user213855
    Hi there! I have a question about how Hibernate persists entity relations. Let's say I have an entity A that has a relation with entity B and another one with entity C. I create an A instance and populate it with new instances of B and C. When I persist A I need C to be persisted previous to B. Is there any way of doing this? Thanks a lot.

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  • Optimum size of transaction in Postgres?

    - by Joe
    I'm running a process that does a lot of updates ( 100,000) to a table. I have the choice between putting all the updates in a single transaction or committing transactions every 1000 or so. Ignore for the moment the case where a transaction fails and is aborted. I'm interested in the best size of transaction for memory and speed efficiency.

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  • Alternatives to HTML for website creation?

    - by Pat
    Hello It seems the most common aproach to web design is to use HTML/XHTML & CSS in conjunction with other technologies or languages like Javascript or PHP. On a theoretical level, I'm interested to know what other languages or technologies could be used to build an entire site without using a single HTML tag or CSS style for styling/positioning? Could a website be made only using XML or PHP alone, including actual styling and positioning? Presumably Flash sites are till embedded in HTML tags? Thanks

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  • transforming binary data using ssis and sql server 2008

    - by Rick
    Hello All - I have a task to import/transform and extract zipped binary files that contain both text data as well as embeded binary data. Within the data is data that is relational in nature and needs to be processed into a defined database structure. Currently I have a C# single threaded app that essentially grabs all the files from the directory (currently there is 13K files of varying sizes) and extracts the data on a single thread line by line inserts to the database. As you could imagine this is a very slow process and unacceptable. There are several different parsing routines used depending on the header record in the file. There are potentially upto a million rows per file when all the data is extracted to the row level of detail. Follow on task is to parse those rows into their appropriate tables based on is content. i.e. the textual content has to be parsed further into "buckets" of like data in the database. That about sums up the big picture. Now for the problem task list. How do i iterate through a packet of data using SSIS? In the app the file is decompressed and then is parsed using streams data type and byte arrays and is routed to the required parsing routine based on the header data of each packet. There is bit swapping involved as well. Should i wrap up the app code into a script task(s) and let it do the custom processing? The data is seperated by year and the sql server tables is partitioned by year as well. I need to be able to "catch" bad file data as well and process by hand most likely. Should i simply load the zipped file to sql as a blob and parse the file with T-SQL? Would that be multi threaded if done that way? Not sure how to do the parsing in tsql that is involved here. Which do you think would be faster? Potentially the data that is currently processed via files could come to us via a socket. Can SSIS collect that data in real time? How would i go about setting that up? Processing these new files from the directorys will become a daily task. I can manage the data once i get it to sql server. Getting it there in a timely fashion seems to be the long pole in the tent for me. I would appreciate any comments or suggestions from the group. Rick

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  • how to detect touch on UIView with UIimage ontop of it?

    - by Silent
    hello all, i want to use a UIview and a UIImage ontop of it with a text box and button i want the user to drag it when the UIview or anything in the view is touched, what would be the best way to implement this method? the UIView is on a single View Controller and using Interface Builder to make my UIviews and UIimages.

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  • How to manage Constants in Application

    - by changed
    what is the best way to use Application Constants ? What i usually do is create a separate table in database of constants and reference them as foreign key in other table. In Java i use enum. But how to keep a single place of authority for constants in application and what are the different ways i can do that(like table or enum).

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  • Java - Runtime.getRuntime().exec() what's going on?

    - by kunkanwan
    Hi, I have problem with Runtime.exec() in Java My code: String lol = "/home/pc/example.txt"; String[] b = {"touch", lol}; try { Runtime.getRuntime().exec(b); } catch(Exception ex) { doSomething(ex); } It's working good but when I trying changle variable "lol" files doesn't create in hard disk for instance: String lol = x.getPath(); where getPath() returns String What should I do ? Thanks for your reply :)

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  • Delegating Struts action class management to Spring raises MTIA critical voilation in Findbugs

    - by shabeer
    When i use "Delegate Struts Action management to Spring" approach explained in http://www.ibm.com/developerworks/java/library/j-sr2.html#N101B7 things work fine in terms of functionality but findbugs reports following voilation Dodgy - Class extends Struts Action class and uses instance variables:MTIA I have bean dependencies injected into action class through spring . Please help me and suggest me a cleaner way to solve this problem. Thanks

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  • embedded Italic, bold fonts don't look the same in flex as in Windows...

    - by Mark
    ...unless they're something like "Times New Roman" or some other established font with a fully designed italic and bold, presumably in seperate files. Let me explain what I mean (though why no one has commented on this before I have no idea.) Numerous, numerous fonts do not have a seperate file for italic and bold, and in fact to the best of my knowledge don't even have italic and bold defined as such. But if you install them on windows (for example) and then use them in an app, You can still make use of italic and bold with those fonts. For italic, and oblique angle is just given to it, presumably by Windows, and it looks the same in all Windows apps, and the bold is just given a heavier weight. OK, well here's the problem: if you embed a font like that in a Flex app, as a "SystemFont" the italic and bold will not look the same as they do in Windows. Specifically, the oblique angle is invariably much less than in Windows (i.e the italic slant is much less) and the bold version is not bold enough. I vaguely recall thinking that there was some flex mechanism to assign custom oblique angles for italic (and weight for bold) but now can't recall what it is. Does anyone know the correct established way to do this. The following is actually a seperate (but related) font question (in case anyone is expert in all this.) Its rather a lengthy question and can be skipped, but its something that's plagued me for a long time. I mention above embedding as a "SystemFont", so iow something like this: package fonts { import flash.display.Sprite; public class FLW_Script_I extends Sprite { [Embed(systemFont='FLW Script', fontName='FLW Script', fontStyle='italic', fntWeight='normal', mimeType='application/x-font-truetype')] public var wrFont:Class; } } The other alternative to SystemFont for embedding, is "Source" followed by the name of an actual font file. If you try to embed one of the aformentioned single file fonts as a Source file (as opposed to SystemFont) and specify fontStyle='italic', then the mxmlc compiler will return an error and say there is no italic info in the font file. So up to now I have only been embedding these fonts as "SystemFont". The problem is, flex uses two different font compilers internally for Source embedding and SystemFont embedding. For source font embeds it uses the "Batik" compiler and for SystemFont, the JRE (Java Runtime) font compiler. Well actually the Batik is considered a superior compiler and generally produces better looking fonts. And also if you mix normal fonts compiled with Batik and italic compiled with JRE, sometimes the line spacing is different for the two, and it doesn't look right. So does anyone have an idea how to get mxmlc to do italic and bold for these single file fonts when embedding as "Source". Would there be a way using C++ or whatever to construct an "italic" font file from the SystemFont for such a font in windows.

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