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  • Syntax for documenting JSON structure

    - by Roman A. Taycher
    So I'm trying to document the format of the json returned by an api I am writing against and I'd like to know if there is any popular format for the documentation of json structure. Note I'm not trying to to test or validate anything, I'm just using this for documentation. Also some ways to add comments to non-constants(items always returned w/ the same value) would be nice. This the not totally thought out scheme I'm currently using: Plain names refer to identifiers or types. Some types have type-comment Strings that appear to be constant(always returned for that type of request) strings are "str" Constant Numbers would be just the number Constant null is null Booleans are true/false for constant booleans or Boolean otherwise [a,b,c] are lists with 3 items a,b,c [... ...] is a list of repeating elements of some types/constants/patterns {a:A,b:B,c:c} and {... ...} is the same for a dictionary. example: story := [header,footer] header := {"data":realHeader,"kind":"Listing"} realHeader := {"after": null, "before": null, "children": [{"data": realRealHeader, "kind": "t3"}], "modhash": ""} footer := {"data":AlmostComments,"kind":"Listing"} AlmostComments := {"data": {"after": null, "before": null, "children": comments, "modhash": ""}, "kind": "t1"} comments := [...{"data":comment, "kind":"t1"}...] realRealHeader := {"author": string, "clicked": boolean, "created": int, "created_utc": int, "domain": "code.reddit.com", "downs": int, "hidden": boolean, "id": string-id, "is_self": boolean, "levenshtein": null, "likes": null, "media": null, "media_embed": { }, "name": string-id, "num_comments": int, "over_18": false, "permalink": string-urlLinkToStoryStartingFrom/r, "saved": false, "score": int, "selftext": string, "selftext_html": string-html, "subreddit": string-subredditname, "subreddit_id": string-id, "thumbnail": "", "title": string, "ups": int, "url": "http://code.reddit.com/" } comments := { "author": string, "body": string-body_html-wout-html, "body_html": string-html-formated, "created": int, "created_utc": int, "downs": int, "id": string-id, "levenshtein": null, "likes": null, "link_id": string-id, "name": string-id", "parent_id": string-id, "replies": AlmostComments or null, "subreddit": string-subredditname, "subreddit_id": string-id, "ups": int }

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  • Avoiding repeated subqueries when 'WITH' is unavailable

    - by EloquentGeek
    MySQL v5.0.58. Tables, with foreign key constraints etc and other non-relevant details omitted for brevity: CREATE TABLE `fixture` ( `id` int(11) NOT NULL auto_increment, `competition_id` int(11) NOT NULL, `name` varchar(50) NOT NULL, `scheduled` datetime default NULL, `played` datetime default NULL, PRIMARY KEY (`id`) ); CREATE TABLE `result` ( `id` int(11) NOT NULL auto_increment, `fixture_id` int(11) NOT NULL, `team_id` int(11) NOT NULL, `score` int(11) NOT NULL, `place` int(11) NOT NULL, PRIMARY KEY (`id`) ); CREATE TABLE `team` ( `id` int(11) NOT NULL auto_increment, `name` varchar(50) NOT NULL, PRIMARY KEY (`id`) ); Where: A draw will set result.place to 0 result.place will otherwise contain an integer representing first place, second place, and so on The task is to return a string describing the most recently played result in a given competition for a given team. The format should be "def Team X,Team Y" if the given team was victorious, "lost to Team X" if the given team lost, and "drew with Team X" if there was a draw. And yes, in theory there could be more than two teams per fixture (though 1 v 1 will be the most common case). This works, but feels really inefficient: SELECT CONCAT( (SELECT CASE `result`.`place` WHEN 0 THEN "drew with" WHEN 1 THEN "def" ELSE "lost to" END FROM `result` WHERE `result`.`fixture_id` = (SELECT `fixture`.`id` FROM `fixture` LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id` WHERE `fixture`.`competition_id` = 2 AND `result`.`team_id` = 1 ORDER BY `fixture`.`played` DESC LIMIT 1) AND `result`.`team_id` = 1), ' ', (SELECT GROUP_CONCAT(`team`.`name`) FROM `fixture` LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id` LEFT JOIN `team` ON `result`.`team_id` = `team`.`id` WHERE `fixture`.`id` = (SELECT `fixture`.`id` FROM `fixture` LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id` WHERE `fixture`.`competition_id` = 2 AND `result`.`team_id` = 1 ORDER BY `fixture`.`played` DESC LIMIT 1) AND `team`.`id` != 1) ) Have I missed something really obvious, or should I simply not try to do this in one query? Or does the current difficulty reflect a poor table design?

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  • Is it possible to have a mysql table accept a null value for a primary_key column referencing a diff

    - by Dr.Dredel
    I have a table that has a column which holds the id of a row in another table. However, when table A is being populated, table B may or may not have a row ready for table A. My question is, is it possible to have mysql prevent an invalid value from being entered but be ok with a NULL? or does a foreign key necessitate a valid related value? So... what I'm looking for (in pseudo code) is this: Table "person" id | name Table "people" id | group_name | person_id (foreign key id from table person) insert into person (1, 'joe'); insert into people (1, 'foo', 1)//kosher insert into people (1, 'foo', NULL)//also kosher insert into people(1, 'foo', 7)// should fail since there is no id 7 in the person table. The reason I need this is that I'm having a chicken and egg issue where it makes perfect sense for the rows in the people table to be created before hand (in this example, I'm creating the groups and would like them to pre-exist the people who join them). And I realize that THIS example is silly and I would just put the group id in the person table rather than vice-versa, but in my real-world problem that is not workable. Just curious if I need to allow any and all values in order to make this work, or if there's some way to allow for null.

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  • slow mysql count because of subselect

    - by frgt10
    how to make this select statement more faster? the first left join with the subselect is making it slower... mysql> SELECT COUNT(DISTINCT w1.id) AS AMOUNT FROM tblWerbemittel w1 JOIN tblVorgang v1 ON w1.object_group = v1.werbemittel_id INNER JOIN ( SELECT wmax.object_group, MAX( wmax.object_revision ) wmaxobjrev FROM tblWerbemittel wmax GROUP BY wmax.object_group ) AS wmaxselect ON w1.object_group = wmaxselect.object_group AND w1.object_revision = wmaxselect.wmaxobjrev LEFT JOIN ( SELECT vmax.object_group, MAX( vmax.object_revision ) vmaxobjrev FROM tblVorgang vmax GROUP BY vmax.object_group ) AS vmaxselect ON v1.object_group = vmaxselect.object_group AND v1.object_revision = vmaxselect.vmaxobjrev LEFT JOIN tblWerbemittel_has_tblAngebot wha ON wha.werbemittel_id = w1.object_group LEFT JOIN tblAngebot ta ON ta.id = wha.angebot_id LEFT JOIN tblLieferanten tl ON tl.id = ta.lieferant_id AND wha.zuschlag = (SELECT MAX(zuschlag) FROM tblWerbemittel_has_tblAngebot WHERE werbemittel_id = w1.object_group) WHERE w1.flags =0 AND v1.flags=0; +--------+ | AMOUNT | +--------+ | 1982 | +--------+ 1 row in set (1.30 sec) Some indexes has been already set and as EXPLAIN shows they were used. +----+--------------------+-------------------------------+--------+----------------------------------------+----------------------+---------+-----------------------------------------------+------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+--------------------+-------------------------------+--------+----------------------------------------+----------------------+---------+-----------------------------------------------+------+----------------------------------------------+ | 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 2072 | | | 1 | PRIMARY | v1 | ref | werbemittel_group,werbemittel_id_index | werbemittel_group | 4 | wmaxselect.object_group | 2 | Using where | | 1 | PRIMARY | <derived3> | ALL | NULL | NULL | NULL | NULL | 3376 | | | 1 | PRIMARY | w1 | eq_ref | object_revision,or_og_index | object_revision | 8 | wmaxselect.wmaxobjrev,wmaxselect.object_group | 1 | Using where | | 1 | PRIMARY | wha | ref | PRIMARY,werbemittel_id_index | werbemittel_id_index | 4 | dpd.w1.object_group | 1 | | | 1 | PRIMARY | ta | eq_ref | PRIMARY | PRIMARY | 4 | dpd.wha.angebot_id | 1 | | | 1 | PRIMARY | tl | eq_ref | PRIMARY | PRIMARY | 4 | dpd.ta.lieferant_id | 1 | Using index | | 4 | DEPENDENT SUBQUERY | tblWerbemittel_has_tblAngebot | ref | PRIMARY,werbemittel_id_index | werbemittel_id_index | 4 | dpd.w1.object_group | 1 | | | 3 | DERIVED | vmax | index | NULL | object_revision_uq | 8 | NULL | 4668 | Using index; Using temporary; Using filesort | | 2 | DERIVED | wmax | range | NULL | or_og_index | 4 | NULL | 2168 | Using index for group-by | +----+--------------------+-------------------------------+--------+----------------------------------------+----------------------+---------+-----------------------------------------------+------+----------------------------------------------+ 10 rows in set (0.01 sec) The main problem while the statement above takes about 2 seconds seems to be the subselect where no index can be used. How to write the statement even more faster? Thanks for help. MT

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  • Why does my SQL database not work in Android?

    - by user1426967
    In my app a click on an image button brings you to the gallery. After clicking on an image I want to call onActivityResult to store the image path. But it does not work. In my LogCat it always tells me that it crashes when it tries to save the image path. Can you find the problem? My onActivityResult method: mImageRowId = savedInstanceState != null ? savedInstanceState.getLong(ImageAdapter.KEY_ROWID) : null; @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { if(requestCode == PICK_FROM_FILE && data != null && data.getData() != null) { Uri uri = data.getData(); if(uri != null) { Cursor cursor = getContentResolver().query(uri, new String[] { android.provider.MediaStore.Images.ImageColumns.DATA}, null, null, null); cursor.moveToFirst(); String image = cursor.getString(0); cursor.close(); if(image != null) { // HERE IS WHERE I WANT TO SAVE THE IMAGE. HERE MUST BE THE ERROR! if (mImageRowId == null) { long id = mImageHelper.createImage(image); if (id > 0) { mImageRowId = id; } } // Set the image and display it in the edit activity Bitmap bitmap = BitmapFactory.decodeFile(image); mImageButton.setImageBitmap(bitmap); } } } } This is my onSaveInstanceState method: private static final Long DEF_ROW_ID = 0L; @Override protected void onSaveInstanceState(Bundle outState) { outState.putLong(ImageAdapter.KEY_ROWID, mImageRowId != null ? mImageRowId : DEF_ROW_ID); super.onSaveInstanceState(outState); } This is a part from my DbAdapter: public long createImage(String image) { ContentValues cv = new ContentValues(); cv.put(KEY_IMAGE, image); return mImageDb.insert(DATABASE_TABLE, null, cv); }

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  • Null pointer to struct which has zero size (empty)... It is a good practice?

    - by ProgramWriter
    Hi2All.. I have some null struct, for example: struct null_type { NullType& someNonVirtualMethod() { return *this; } }; And in some function i need to pass reference to this type. Reason: template <typename T1 = null_type, typename T2 = null_type, ... > class LooksLikeATupleButItsNotATuple { public: LooksLikeATupleButItsNotATuple(T1& ref1 = defParamHere, T2& ref2 = andHere..) : _ref1(ref1), _ref2(ref2), ... { } void someCompositeFunctionHere() { _ref1.someNonVirtualMethod(); _ref2.someNonVirtualMethod(); ... } private: T1& _ref1; T2& _ref2; ...; }; It is a good practice to use null reference as a default parameter?: *static_cast<NullType*>(0) It works on MSVC, but i have some doubts...

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  • Ubuntu 12.04.1 LTS -touch pad scroll for asus-k55v not working

    - by Aks
    have tried all the commands over terminal but still could bot fix it, for xinput i got Virtual core pointer id=2 [master pointer (3)] ? ? Virtual core XTEST pointer id=4 [slave pointer (2)] ? ? MOSART Semi. 2.4G Keyboard Mouse id=11 [slave pointer (2)] ? ? PS/2 Generic Mouse id=15 [slave pointer (2)] ? Virtual core keyboard id=3 [master keyboard (2)] ? Virtual core XTEST keyboard id=5 [slave keyboard (3)] ? Power Button id=6 [slave keyboard (3)] ? Video Bus id=7 [slave keyboard (3)] ? Video Bus id=8 [slave keyboard (3)] ? Sleep Button id=9 [slave keyboard (3)] ? MOSART Semi. 2.4G Keyboard Mouse id=10 [slave keyboard (3)] ? USB 2.0 UVC HD Webcam id=12 [slave keyboard (3)] ? Asus WMI hotkeys id=13 [slave keyboard (3)] ? AT Translated Set 2 keyboard id=14 [slave keyboard (3)] none of the post cud help to fix it :( help

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  • Touchpad is recognized but not working on Toshiba P855-S5312 - Ubuntu 12.10

    - by user107942
    i just made a new fresh install of ubuntu 12.10, everything works nice but the touchpad istn working, it is recognized but it is not working, here a paste bin of what i get when I type "xinput list" http://paste.ubuntu.com/1357219/ b0w@b0w:~$ xinput list ? Virtual core pointer id=2 [master pointer (3)] ? ? Virtual core XTEST pointer id=4 [slave pointer (2)] ? ? Genius Optical Mouse id=9 [slave pointer (2)] ? ? SynPS/2 Synaptics TouchPad id=12 [slave pointer (2)] ? Virtual core keyboard id=3 [master keyboard (2)] ? Virtual core XTEST keyboard id=5 [slave keyboard (3)] ? Power Button id=6 [slave keyboard (3)] ? Video Bus id=7 [slave keyboard (3)] ? Power Button id=8 [slave keyboard (3)] ? TOSHIBA Web Camera - HD id=10 [slave keyboard (3)] ? AT Translated Set 2 keyboard id=11 [slave keyboard (3)] ? Toshiba input device id=13 [slave keyboard (3)] b0w@b0w:~$

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  • Why do I get a null pointer exception from TabWidget?

    - by rushinge
    I'm writing an android program in which I have an activity that uses tabs. The Activity public class UnitActivity extends TabActivity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); TabHost tabHost = getTabHost(); TabSpec spec; Resources res = getResources(); LayoutInflater.from(this).inflate(R.layout.unit_view, tabHost.getTabContentView(), true); spec = tabHost.newTabSpec("controls"); spec.setIndicator("Control", res.getDrawable(R.drawable.ic_tab_equalizer)); spec.setContent(R.id.txtview); tabHost.addTab(spec); } } The XML referenced by R.layout.unit_view <?xml version="1.0" encoding="utf-8"?> <TabHost xmlns:android="http://schemas.android.com/apk/res/android" android:id="@android:id/tabhost" android:layout_width="fill_parent" android:layout_height="fill_parent"> <LinearLayout android:layout_width="fill_parent" android:layout_height="fill_parent" android:padding="5dp"> <TabWidget android:id="@android:id/tabs" android:layout_width="fill_parent" android:layout_height="wrap_content"/> <FrameLayout android:id="@android:id/tabcontent" android:layout_width="fill_parent" android:layout_height="fill_parent" android:padding="5dp"> <TextView android:id="@+id/txtview" android:layout_width="fill_parent" android:layout_height="fill_parent" android:gravity="bottom" android:text="nullpointer this!" /> </FrameLayout> </LinearLayout> </TabHost> As far as I can see I'm doing the same thing I see in the tabs1 api sample from the android sdk. I've tried "getLayoutInflator()" instead of "LayoutInflator.from(this)" with the same result. If I replace the LayoutInflater line with "setContentView(R.layout.unit_view)" my program doesn't crash with a null pointer exception but my content is completely blank and empty. I get the tab and that's it. I've checked to make sure R.layout.unit_view and tabHost are not null when it runs the LayoutInflater line and they seem to be fine. They're defenitely not null. I've also checked to make sure LayoutInflater.from(this) returns a valid layout inflater object and it does. The logcat indicating the error says E/AndroidRuntime( 541): java.lang.NullPointerException E/AndroidRuntime( 541): at android.widget.TabWidget.dispatchDraw(TabWidget.java:206) E/AndroidRuntime( 541): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) E/AndroidRuntime( 541): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) E/AndroidRuntime( 541): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) E/AndroidRuntime( 541): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) E/AndroidRuntime( 541): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) E/AndroidRuntime( 541): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) E/AndroidRuntime( 541): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) E/AndroidRuntime( 541): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) E/AndroidRuntime( 541): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) E/AndroidRuntime( 541): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) E/AndroidRuntime( 541): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) E/AndroidRuntime( 541): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) E/AndroidRuntime( 541): at android.view.View.draw(View.java:6538) E/AndroidRuntime( 541): at android.widget.FrameLayout.draw(FrameLayout.java:352) E/AndroidRuntime( 541): at android.view.ViewGroup.drawChild(ViewGroup.java:1531) E/AndroidRuntime( 541): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) E/AndroidRuntime( 541): at android.view.ViewGroup.drawChild(ViewGroup.java:1529) E/AndroidRuntime( 541): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1258) E/AndroidRuntime( 541): at android.view.View.draw(View.java:6538) E/AndroidRuntime( 541): at android.widget.FrameLayout.draw(FrameLayout.java:352) E/AndroidRuntime( 541): at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1830) E/AndroidRuntime( 541): at android.view.ViewRoot.draw(ViewRoot.java:1349) E/AndroidRuntime( 541): at android.view.ViewRoot.performTraversals(ViewRoot.java:1114) E/AndroidRuntime( 541): at android.view.ViewRoot.handleMessage(ViewRoot.java:1633) E/AndroidRuntime( 541): at android.os.Handler.dispatchMessage(Handler.java:99) E/AndroidRuntime( 541): at android.os.Looper.loop(Looper.java:123) E/AndroidRuntime( 541): at android.app.ActivityThread.main(ActivityThread.java:4363) E/AndroidRuntime( 541): at java.lang.reflect.Method.invokeNative(Native Method) E/AndroidRuntime( 541): at java.lang.reflect.Method.invoke(Method.java:521) E/AndroidRuntime( 541): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) E/AndroidRuntime( 541): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) E/AndroidRuntime( 541): at dalvik.system.NativeStart.main(Native Method) I/Process ( 61): Sending signal. PID: 541 SIG: 3 I/dalvikvm( 541): threadid=7: reacting to signal 3 I/dalvikvm( 541): Wrote stack trace to '/data/anr/traces.txt' Anybody have any idea how I can get this content into a tab without crashing my application? My actual program is more complex and has more than one tab but I simplified it down to this in an attempt to find out why it's crashing but it still crashes and I don't know why. If I don't use LayoutInflator my program doesn't crash but I don't get any content either, just tabs.

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  • Translate ImageButton from C# to XAML

    - by Bill
    I worked out the C# code to create an ImageButton (below) that has three images (one base-image and two overlays) and three text boxes as the face of the button. I am inheriting from the Button class, which unfortunately includes several components that I didn't realize would surface until after coding and need to remove, namely the bright-blue surrounding border on IsMouseOver, and any visible borders between the buttons, as the buttons will end up in a wrapPanel and the borders need to be seamless. Now that the format has been worked out in C#, I expect that I need to translate to XAML so that I can create a ControlTemplate to get the functionality necessary, however I am not certain as to the process of translating from C# to XAML. Can anyone steer me in the right direction? public class ACover : Button { Image cAImage = null; Image jCImage = null; Image jCImageOverlay = null; TextBlock ATextBlock = null; TextBlock AbTextBlock = null; TextBlock ReleaseDateTextBlock = null; private string _TracksXML = ""; public ACover() { Grid cArtGrid = new Grid(); cArtGrid.Background = new SolidColorBrush(Color.FromRgb(38, 44, 64)); cArtGrid.Margin = new System.Windows.Thickness(5, 10, 5, 10); RowDefinition row1 = new RowDefinition(); row1.Height = new GridLength(225); RowDefinition row2 = new RowDefinition(); row2.Height = new GridLength(0, GridUnitType.Auto); RowDefinition row3 = new RowDefinition(); row3.Height = new GridLength(0, GridUnitType.Auto); RowDefinition row4 = new RowDefinition(); row4.Height = new GridLength(0, GridUnitType.Auto); cArtGrid.RowDefinitions.Add(row1); cArtGrid.RowDefinitions.Add(row2); cArtGrid.RowDefinitions.Add(row3); cArtGrid.RowDefinitions.Add(row4); ColumnDefinition col1 = new ColumnDefinition(); col1.Width = new GridLength(0, GridUnitType.Auto); cArtGrid.ColumnDefinitions.Add(col1); jCImage = new Image(); jCImage.Height = 240; jCImage.Width = 260; jCImage.VerticalAlignment = VerticalAlignment.Top; jCImage.Source = new BitmapImage(new Uri(Properties.Settings.Default.pathToGridImages + "jc.png", UriKind.Absolute)); cArtGrid.Children.Add(jCImage); cArtImage = new Image(); cArtImage.Height = 192; cArtImage.Width = 192; cArtImage.Margin = new System.Windows.Thickness(3, 7, 0, 0); cArtImage.VerticalAlignment = VerticalAlignment.Top; cArtGrid.Children.Add(cArtImage); jCImageOverlay = new Image(); jCImageOverlay.Height = 192; jCImageOverlay.Width = 192; jCImageOverlay.Margin = new System.Windows.Thickness(3, 7, 0, 0); jCImageOverlay.VerticalAlignment = VerticalAlignment.Top; jCImageOverlay.Source = new BitmapImage(new Uri( Properties.Settings.Default.pathToGridImages + "jc-overlay.png", UriKind.Absolute)); coverArtGrid.Children.Add(jCImageOverlay); ATextBlock = new TextBlock(); ATextBlock.Foreground = new SolidColorBrush(Color.FromRgb(173, 176, 198)); ATextBlock.Margin = new Thickness(10, -10, 0, 0); cArtGrid.Children.Add(ATextBlock); AlTextBlock = new TextBlock(); AlTextBlock.Margin = new Thickness(10, 0, 0, 0); AlTextBlock.Foreground = new SolidColorBrush(Color.FromRgb(173, 176, 198)); cArtGrid.Children.Add(AlTextBlock); RDTextBlock = new TextBlock(); RDTextBlock.Margin = new Thickness(10, 0, 0, 0); RDTextBlock.Foreground = new SolidColorBrush(Color.FromRgb(173, 176, 198)); cArtGrid.Children.Add(RDTextBlock); Grid.SetColumn(jCImage, 0); Grid.SetRow(jCImage, 0); Grid.SetColumn(jCImageOverlay, 0); Grid.SetRow(jCImageOverlay, 0); Grid.SetColumn(cArtImage, 0); Grid.SetRow(cArtImage, 0); Grid.SetColumn(ATextBlock, 0); Grid.SetRow(ATextBlock, 1); Grid.SetColumn(AlTextBlock, 0); Grid.SetRow(AlTextBlock, 2); Grid.SetColumn(RDTextBlock, 0); Grid.SetRow(RDTextBlock, 3); this.Content = cArtGrid; } public string A { get { if (ATextBlock != null) return ATextBlock.Text; else return String.Empty; } set { if (ATextBlock != null) ATextBlock.Text = value; } } public string Al { get { if (AlTextBlock != null) return AlTextBlock.Text; else return String.Empty; } set { if (AlTextBlock != null) AlTextBlock.Text = value; } } public string RD { get { if (RDTextBlock != null) return RDTextBlock.Text; else return String.Empty; } set { if (RDTextBlock != null) RDTextBlock.Text = value; } } public ImageSource Image { get { if (cArtImage != null) return cArtImage.Source; else return null; } set { if (cArtImage != null) cArtImage.Source = value; } } public string TracksXML { get { return _TracksXML; } set { _TracksXML = value; } } public double ImageWidth { get { if (cArtImage != null) return cArtImage.Width; else return double.NaN; } set { if (cArtImage != null) cArtImage.Width = value; } } public double ImageHeight { get { if (cArtImage != null) return cArtImage.Height; else return double.NaN; } set { if (cArtImage != null) cArtImage.Height = value; } } }

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  • Largest sphere inside a frustum

    - by Will
    How do you find the largest sphere that you can draw in perspective? Viewed from the top, it'd be this: Added: on the frustum on the right, I've marked four points I think we know something about. We can unproject all eight corners of the frusum, and the centres of the near and far ends. So we know point 1, 3 and 4. We also know that point 2 is the same distance from 3 as 4 is from 3. So then we can compute the nearest point on the line 1 to 4 to point 2 in order to get the centre? But the actual math and code escapes me. I want to draw models (which are approximately spherical and which I have a miniball bounding sphere for) as large as possible. Update: I've tried to implement the incircle-on-two-planes approach as suggested by bobobobo and Nathan Reed : function getFrustumsInsphere(viewport,invMvpMatrix) { var midX = viewport[0]+viewport[2]/2, midY = viewport[1]+viewport[3]/2, centre = unproject(midX,midY,null,null,viewport,invMvpMatrix), incircle = function(a,b) { var c = ray_ray_closest_point_3(a,b); a = a[1]; // far clip plane b = b[1]; // far clip plane c = c[1]; // camera var A = vec3_length(vec3_sub(b,c)), B = vec3_length(vec3_sub(a,c)), C = vec3_length(vec3_sub(a,b)), P = 1/(A+B+C), x = ((A*a[0])+(B*a[1])+(C*a[2]))*P, y = ((A*b[0])+(B*b[1])+(C*b[2]))*P, z = ((A*c[0])+(B*c[1])+(C*c[2]))*P; c = [x,y,z]; // now the centre of the incircle c.push(vec3_length(vec3_sub(centre[1],c))); // add its radius return c; }, left = unproject(viewport[0],midY,null,null,viewport,invMvpMatrix), right = unproject(viewport[2],midY,null,null,viewport,invMvpMatrix), horiz = incircle(left,right), top = unproject(midX,viewport[1],null,null,viewport,invMvpMatrix), bottom = unproject(midX,viewport[3],null,null,viewport,invMvpMatrix), vert = incircle(top,bottom); return horiz[3]<vert[3]? horiz: vert; } I admit I'm winging it; I'm trying to adapt 2D code by extending it into 3 dimensions. It doesn't compute the insphere correctly; the centre-point of the sphere seems to be on the line between the camera and the top-left each time, and its too big (or too close). Is there any obvious mistakes in my code? Does the approach, if fixed, work?

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  • How to calculate the covariance in T-SQL

    - by Peter Larsson
    DECLARE @Sample TABLE         (             x INT NOT NULL,             y INT NOT NULL         ) INSERT  @Sample VALUES  (3, 9),         (2, 7),         (4, 12),         (5, 15),         (6, 17) ;WITH cteSource(x, xAvg, y, yAvg, n) AS (         SELECT  1E * x,                 AVG(1E * x) OVER (PARTITION BY (SELECT NULL)),                 1E * y,                 AVG(1E * y) OVER (PARTITION BY (SELECT NULL)),                 COUNT(*) OVER (PARTITION BY (SELECT NULL))         FROM    @Sample ) SELECT  SUM((x - xAvg) *(y - yAvg)) / MAX(n) AS [COVAR(x,y)] FROM    cteSource

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  • SpringMvc java.lang.NullPointerException When Posting Form To Server [closed]

    - by dev_darin
    I have a form with a user name field on it when i tab out of the field i use a RESTFUL Web Service that makes a call to a handler method in the controller. The method makes a call to a DAO class that checks the database if the user name exists. This works fine, however when the form is posted to the server i call the same exact function i would call in the handler method however i get a java.lang.NullPointerException when it accesses the class that makes a call to the DAO object. So it does not even access the DAO object the second time. I have exception handlers around the calls in all my classes that makes calls. Any ideas as to whats happening here why i would get the java.lang.NullPointerException the second time the function is called.Does this have anything to do with Spring instantiating DAO classes using a Singleton method or something to that effect? What can be done to resolve this? This is what happens the First Time The Method is called using the Web Service(this is suppose to happen): 13011 [http-8084-2] INFO com.crimetrack.jdbc.JdbcOfficersDAO - Inside jdbcOfficersDAO 13031 [http-8084-2] DEBUG org.springframework.jdbc.core.JdbcTemplate - Executing prepared SQL query 13034 [http-8084-2] DEBUG org.springframework.jdbc.core.JdbcTemplate - Executing prepared SQL statement [SELECT userName FROM crimetrack.tblofficers WHERE userName = ?] 13071 [http-8084-2] DEBUG org.springframework.jdbc.datasource.DataSourceUtils - Fetching JDBC Connection from DataSource 13496 [http-8084-2] DEBUG org.springframework.jdbc.core.StatementCreatorUtils - Setting SQL statement parameter value: column index 1, parameter value [adminz], value class [java.lang.String], SQL type unknown 13534 [http-8084-2] DEBUG org.springframework.jdbc.datasource.DataSourceUtils - Returning JDBC Connection to DataSource 13537 [http-8084-2] INFO com.crimetrack.jdbc.JdbcOfficersDAO - No username was found in exception 13537 [http-8084-2] INFO com.crimetrack.service.ValidateUserNameManager - UserName :adminz does NOT exist The Second time When The Form Is 'Post' and a validation method handles the form and calls the same method the web service would call: 17199 [http-8084-2] INFO com.crimetrack.service.OfficerRegistrationValidation - UserName is not null so going to check if its valid for :adminz 17199 [http-8084-2] INFO com.crimetrack.service.OfficerRegistrationValidation - User Name in try.....catch block is adminz 17199 [http-8084-2] INFO com.crimetrack.service.ValidateUserNameManager - Inside Do UserNameExist about to validate with username : adminz 17199 [http-8084-2] INFO com.crimetrack.service.ValidateUserNameManager - UserName :adminz EXCEPTION OCCURED java.lang.NullPointerException ValidateUserNameManager.java public class ValidateUserNameManager implements ValidateUserNameIFace { private OfficersDAO officerDao; private final Logger logger = Logger.getLogger(getClass()); public boolean DoesUserNameExist(String userName) throws Exception { logger.info("Inside Do UserNameExist about to validate with username : " + userName); try{ if(officerDao.OfficerExist(userName) == true){ logger.info("UserName :" + userName + " does exist"); return true; }else{ logger.info("UserName :" + userName + " does NOT exist"); return false; } }catch(Exception e){ logger.info("UserName :" + userName + " EXCEPTION OCCURED " + e.toString()); return false; } } /** * @return the officerDao */ public OfficersDAO getOfficerDao() { return officerDao; } /** * @param officerdao the officerDao to set */ public void setOfficerDao(OfficersDAO officerDao) { this.officerDao = officerDao; } } JdbcOfficersDAO.java public boolean OfficerExist(String userName){ String dbUserName; try{ logger.info("Inside jdbcOfficersDAO"); String sql = "SELECT userName FROM crimetrack.tblofficers WHERE userName = ?"; try{ dbUserName = (String)getJdbcTemplate().queryForObject(sql, new Object[]{userName},String.class); logger.info("Just Returned from database"); }catch(Exception e){ logger.info("No username was found in exception"); return false; } if(dbUserName == null){ logger.info("Database did not find any matching records"); } logger.info("after JdbcTemplate"); if (dbUserName.equals(userName)) { logger.info("User Name Exists"); return true; }else{ logger.info("User Name Does NOT Exists"); return false; } }catch(Exception e){ logger.info("Exception Message in JdbcOfficersDAO is "+e.getMessage()); return false; } } OfficerRegistrationValidation.java public class OfficerRegistrationValidation implements Validator{ private final Logger logger = Logger.getLogger(getClass()); private ValidateUserNameManager validateUserNameManager; public boolean supports(Class<?> clazz) { return Officers.class.equals(clazz); } public void validate(Object target, Errors errors) { Officers officer = (Officers) target; if (officer.getUserName() == null){ errors.rejectValue("userName", "userName.required"); }else{ String userName = officer.getUserName(); logger.info("UserName is not null so going to check if its valid for :" + userName); try { logger.info("User Name in try.....catch block is " + userName); if (validateUserNameManager.DoesUserNameExist(userName)== true){ errors.rejectValue("userName", "userName.exist"); } } catch (Exception e) { logger.info("Error Occured When validating UserName"); errors.rejectValue("userName", "userName.error"); } } if(officer.getPassword()== null){ errors.rejectValue("password", "password.required"); } if(officer.getPassword2()== null){ errors.rejectValue("password2", "password2.required"); } if(officer.getfName() == null){ errors.rejectValue("fName","fName.required"); } if(officer.getlName() == null){ errors.rejectValue("lName", "lName.required"); } if (officer.getoName() == null){ errors.rejectValue("oName", "oName.required"); } if (officer.getEmailAdd() == null){ errors.rejectValue("emailAdd", "emailAdd.required"); } if (officer.getDob() == null){ errors.rejectValue("dob", "dob.required"); } if (officer.getGenderId().equals("A")){ errors.rejectValue("genderId","genderId.required"); } if(officer.getDivisionNo() == 1){ errors.rejectValue("divisionNo", "divisionNo.required"); } if(officer.getPositionId() == 1){ errors.rejectValue("positionId", "positionId.required"); } if (officer.getStartDate() == null){ errors.rejectValue("startDate","startDate.required"); } if(officer.getEndDate() == null){ errors.rejectValue("endDate","endDate.required"); } logger.info("The Gender ID is " + officer.getGenderId().toString()); if(officer.getPhoneNo() == null){ errors.rejectValue("phoneNo", "phoneNo.required"); } } /** * @return the validateUserNameManager */ public ValidateUserNameManager getValidateUserNameManager() { return validateUserNameManager; } /** * @param validateUserNameManager the validateUserNameManager to set */ public void setValidateUserNameManager( ValidateUserNameManager validateUserNameManager) { this.validateUserNameManager = validateUserNameManager; } } Update Error Log using Logger.Error("Message", e): 39024 [http-8084-2] INFO com.crimetrack.service.OfficerRegistrationValidation - UserName is not null so going to check if its valid for :adminz 39025 [http-8084-2] INFO com.crimetrack.service.OfficerRegistrationValidation - User Name in try.....catch block is adminz 39025 [http-8084-2] ERROR com.crimetrack.service.OfficerRegistrationValidation - Message java.lang.NullPointerException at com.crimetrack.service.OfficerRegistrationValidation.validate(OfficerRegistrationValidation.java:47) at org.springframework.validation.DataBinder.validate(DataBinder.java:725) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.doBind(HandlerMethodInvoker.java:815) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveHandlerArguments(HandlerMethodInvoker.java:367) at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:171) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:436) at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:424) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789) at javax.servlet.http.HttpServlet.service(HttpServlet.java:637) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489) at java.lang.Thread.run(Unknown Source) 39025 [http-8084-2] INFO com.crimetrack.service.OfficerRegistrationValidation - Error Occured When validating UserName

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  • Sql Table Refactoring Challenge

    Ive been working a bit on cleaning up a large table to make it more efficient.  I pretty much know what I need to do at this point, but I figured Id offer up a challenge for my readers, to see if they can catch everything I have as well as to see if Ive missed anything.  So to that end, I give you my table: CREATE TABLE [dbo].[lq_ActivityLog]( [ID] [bigint] IDENTITY(1,1) NOT NULL, [PlacementID] [int] NOT NULL, [CreativeID] [int] NOT NULL, [PublisherID] [int] NOT NULL, [CountryCode] [nvarchar](10) NOT NULL, [RequestedZoneID] [int] NOT NULL, [AboveFold] [int] NOT NULL, [Period] [datetime] NOT NULL, [Clicks] [int] NOT NULL, [Impressions] [int] NOT NULL, CONSTRAINT [PK_lq_ActivityLog2] PRIMARY KEY CLUSTERED ( [Period] ASC, [PlacementID] ASC, [CreativeID] ASC, [PublisherID] ASC, [RequestedZoneID] ASC, [AboveFold] ASC, [CountryCode] ASC)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY] And now some assumptions and additional information: The table has 200,000,000 rows currently PlacementID ranges from 1 to 5000 and should support at least 50,000 CreativeID ranges from 1 to 5000 and should support at least 50,000 PublisherID ranges from 1 to 500 and should support at least 50,000 CountryCode is a 2-character ISO standard (e.g. US) and there is a country table with an integer ID already.  There are < 300 rows. RequestedZoneID ranges from 1 to 100 and should support at least 50,000 AboveFold has values of 1, 0, or 1 only. Period is a date (no time). Clicks range from 0 to 5000. Impressions range from 0 to 5000000. The table is currently write-mostly.  Its primary purpose is to log advertising activity as quickly as possible.  Nothing in the rest of the system reads from it except for batch jobs that pull the data into summary tables. Heres the current information on the database tables size: Design Goals This table has been in use for about 5 years and has performed very well during that time.  The only complaints we have are that it is quite large and also there are occasionally timeouts for queries that reference it, particularly when batch jobs are pulling data from it.  Any changes should be made with an eye toward keeping write performance optimal  while trying to reduce space and improve read performance / eliminate timeouts during read operations. Refactor There are, I suggest to you, some glaringly obvious optimizations that can be made to this table.  And Im sure there are some ninja tweaks known to SQL gurus that would be a big help as well.  Ill post my own suggested changes in a follow-up post for now feel free to comment with your suggestions. Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Sql Table Refactoring Challenge

    Ive been working a bit on cleaning up a large table to make it more efficient.  I pretty much know what I need to do at this point, but I figured Id offer up a challenge for my readers, to see if they can catch everything I have as well as to see if Ive missed anything.  So to that end, I give you my table: CREATE TABLE [dbo].[lq_ActivityLog]( [ID] [bigint] IDENTITY(1,1) NOT NULL, [PlacementID] [int] NOT NULL, [CreativeID] [int] NOT NULL, [PublisherID] [int] NOT NULL, [CountryCode] [nvarchar](10) NOT NULL, [RequestedZoneID] [int] NOT NULL, [AboveFold] [int] NOT NULL, [Period] [datetime] NOT NULL, [Clicks] [int] NOT NULL, [Impressions] [int] NOT NULL, CONSTRAINT [PK_lq_ActivityLog2] PRIMARY KEY CLUSTERED ( [Period] ASC, [PlacementID] ASC, [CreativeID] ASC, [PublisherID] ASC, [RequestedZoneID] ASC, [AboveFold] ASC, [CountryCode] ASC)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY] And now some assumptions and additional information: The table has 200,000,000 rows currently PlacementID ranges from 1 to 5000 and should support at least 50,000 CreativeID ranges from 1 to 5000 and should support at least 50,000 PublisherID ranges from 1 to 500 and should support at least 50,000 CountryCode is a 2-character ISO standard (e.g. US) and there is a country table with an integer ID already.  There are < 300 rows. RequestedZoneID ranges from 1 to 100 and should support at least 50,000 AboveFold has values of 1, 0, or 1 only. Period is a date (no time). Clicks range from 0 to 5000. Impressions range from 0 to 5000000. The table is currently write-mostly.  Its primary purpose is to log advertising activity as quickly as possible.  Nothing in the rest of the system reads from it except for batch jobs that pull the data into summary tables. Heres the current information on the database tables size: Design Goals This table has been in use for about 5 years and has performed very well during that time.  The only complaints we have are that it is quite large and also there are occasionally timeouts for queries that reference it, particularly when batch jobs are pulling data from it.  Any changes should be made with an eye toward keeping write performance optimal  while trying to reduce space and improve read performance / eliminate timeouts during read operations. Refactor There are, I suggest to you, some glaringly obvious optimizations that can be made to this table.  And Im sure there are some ninja tweaks known to SQL gurus that would be a big help as well.  Ill post my own suggested changes in a follow-up post for now feel free to comment with your suggestions. Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Objective-C error... Cannot convert to pointer type (int)

    - by Flash84x
    I am attempting to use the TouchXML library and followed the example with the following code for (CXMLElement node in nodes) { NSMutableDictionary *item = [[NSMutableDictionary alloc] init]; int counter; for (counter = 0; counter < [node childCount]; counter++ ) { [item setObject:[[node childAtIndex:counter] stringValue] forKey:[[node childAtIndex:counter] name]]; } [rst addObject:item]; [item release]; } The compiler however is complaining about counter and throwing the following error for counter = 0 and both occurances in the setObject call. Cannot convert to pointer type Any help with my rusty C/ObjC would be appreciated

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  • iPhone - Get a pointer to the data behind CGDataProvider?

    - by jtrim
    I'm trying to take a CGImage and copy its data into a buffer for later processing. The code below is what I have so far, but there's one thing I don't like about it - it's copying the image data twice. Once for CGDataProviderCopyData() and once for the :getBytes:length call on imgData. I haven't been able to find a way to copy the image data directly into my buffer and cut out the CGDataProviderCopyData() step, but there has to be a way...any pointers? (...pun ftw) NSData *imgData = (NSData *)(CGDataProviderCopyData(CGImageGetDataProvider(myCGImageRef))); CGImageRelease(myCGImageRef); // i've got a previously-defined pointer to an available buffer called "mybuff" [imgData getBytes:mybuff length:[imgData length]];

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  • Null-free "maps": Is a callback solution slower than tryGet()?

    - by David Moles
    In comments to "How to implement List, Set, and Map in null free design?", Steven Sudit and I got into a discussion about using a callback, with handlers for "found" and "not found" situations, vs. a tryGet() method, taking an out parameter and returning a boolean indicating whether the out parameter had been populated. Steven maintained that the callback approach was more complex and almost certain to be slower; I maintained that the complexity was no greater and the performance at worst the same. But code speaks louder than words, so I thought I'd implement both and see what I got. The original question was fairly theoretical with regard to language ("And for argument sake, let's say this language don't even have null") -- I've used Java here because that's what I've got handy. Java doesn't have out parameters, but it doesn't have first-class functions either, so style-wise, it should suck equally for both approaches. (Digression: As far as complexity goes: I like the callback design because it inherently forces the user of the API to handle both cases, whereas the tryGet() design requires callers to perform their own boilerplate conditional check, which they could forget or get wrong. But having now implemented both, I can see why the tryGet() design looks simpler, at least in the short term.) First, the callback example: class CallbackMap<K, V> { private final Map<K, V> backingMap; public CallbackMap(Map<K, V> backingMap) { this.backingMap = backingMap; } void lookup(K key, Callback<K, V> handler) { V val = backingMap.get(key); if (val == null) { handler.handleMissing(key); } else { handler.handleFound(key, val); } } } interface Callback<K, V> { void handleFound(K key, V value); void handleMissing(K key); } class CallbackExample { private final Map<String, String> map; private final List<String> found; private final List<String> missing; private Callback<String, String> handler; public CallbackExample(Map<String, String> map) { this.map = map; found = new ArrayList<String>(map.size()); missing = new ArrayList<String>(map.size()); handler = new Callback<String, String>() { public void handleFound(String key, String value) { found.add(key + ": " + value); } public void handleMissing(String key) { missing.add(key); } }; } void test() { CallbackMap<String, String> cbMap = new CallbackMap<String, String>(map); for (int i = 0, count = map.size(); i < count; i++) { String key = "key" + i; cbMap.lookup(key, handler); } System.out.println(found.size() + " found"); System.out.println(missing.size() + " missing"); } } Now, the tryGet() example -- as best I understand the pattern (and I might well be wrong): class TryGetMap<K, V> { private final Map<K, V> backingMap; public TryGetMap(Map<K, V> backingMap) { this.backingMap = backingMap; } boolean tryGet(K key, OutParameter<V> valueParam) { V val = backingMap.get(key); if (val == null) { return false; } valueParam.value = val; return true; } } class OutParameter<V> { V value; } class TryGetExample { private final Map<String, String> map; private final List<String> found; private final List<String> missing; public TryGetExample(Map<String, String> map) { this.map = map; found = new ArrayList<String>(map.size()); missing = new ArrayList<String>(map.size()); } void test() { TryGetMap<String, String> tgMap = new TryGetMap<String, String>(map); for (int i = 0, count = map.size(); i < count; i++) { String key = "key" + i; OutParameter<String> out = new OutParameter<String>(); if (tgMap.tryGet(key, out)) { found.add(key + ": " + out.value); } else { missing.add(key); } } System.out.println(found.size() + " found"); System.out.println(missing.size() + " missing"); } } And finally, the performance test code: public static void main(String[] args) { int size = 200000; Map<String, String> map = new HashMap<String, String>(); for (int i = 0; i < size; i++) { String val = (i % 5 == 0) ? null : "value" + i; map.put("key" + i, val); } long totalCallback = 0; long totalTryGet = 0; int iterations = 20; for (int i = 0; i < iterations; i++) { { TryGetExample tryGet = new TryGetExample(map); long tryGetStart = System.currentTimeMillis(); tryGet.test(); totalTryGet += (System.currentTimeMillis() - tryGetStart); } System.gc(); { CallbackExample callback = new CallbackExample(map); long callbackStart = System.currentTimeMillis(); callback.test(); totalCallback += (System.currentTimeMillis() - callbackStart); } System.gc(); } System.out.println("Avg. callback: " + (totalCallback / iterations)); System.out.println("Avg. tryGet(): " + (totalTryGet / iterations)); } On my first attempt, I got 50% worse performance for callback than for tryGet(), which really surprised me. But, on a hunch, I added some garbage collection, and the performance penalty vanished. This fits with my instinct, which is that we're basically talking about taking the same number of method calls, conditional checks, etc. and rearranging them. But then, I wrote the code, so I might well have written a suboptimal or subconsicously penalized tryGet() implementation. Thoughts?

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  • Strict pointer aliasing: any solution for a specific problem?

    - by doublep
    I have a problem caused by breaking strict pointer aliasing rule. I have a type T that comes from a template and some integral type Int of the same size (as with sizeof). My code essentially does the following: T x = some_other_t; if (*reinterpret_cast <Int*> (&x) == 0) ... Because T is some arbitary (other than the size restriction) type that could have a constructor, I cannot make a union of T and Int. (This is allowed only in C++0x only and isn't even supported by GCC yet). Is there any way I could rewrite the above pseudocode to preserve functionality and avoid breaking strict aliasing rule? Note that this is a template, I cannot control T or value of some_other_t; the assignment and subsequent comparison do happen inside the templated code. (For the record, the above code started breaking on GCC 4.5 if T contains any bit fields.)

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  • How do you move the pointer up or down multiple lines with Emacs?

    - by Peter
    I can move my pointer up and down one line with my arrow key just fine in Emacs, so I'd like to redefine C-n and C-p to move up and down 5 lines at a time. I'm just beginning to learn how to use Emacs, and elisp is very alien to me. I tried using the GNU Emacs lisp reference, but I couldn't find how to bind a keystroke to multiple commands. Here's what I have so far (concentrating on the moving up definition): (global-set-key "\C-p" '(loop for i in '(1 2 3 4 5) do ('previous-line))) But, this brings up an error message when I hit C-p, "Wrong type argument." Any suggestions? Thanks!

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  • How to attach boost::shared_ptr (or another smart pointer) to reference counter of object's parent?

    - by Checkers
    I remember encountering this concept before, but can't find it in Google now. If I have an object of type A, which directly embeds an object of type B: class A { B b; }; How can I have a smart pointer to B, e. g. boost::shared_ptr<B>, but use reference count of A? Assume an instance of A itself is heap-allocated I can safely get its shared count using, say, enable_shared_from_this.

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  • When should an array name be treated as a pointer and when does it just represent the array itself? [duplicate]

    - by user1087373
    This question already has an answer here: When is an array name or a function name 'converted' into a pointer ? (in C) 4 answers I just made a test program after reading the book and the result turned out confusing: #include <stdio.h> int main(void) { char text[] = "hello!"; printf("sizeof(text):%d sizeof(text+2):%d sizeof(text[0]):%d \n",(int)sizeof(text), sizeof(text+2), sizeof(text[0])); printf("text:%p sizeof(text):%d &text:%p sizeof(&text):%d \n",text, sizeof(text), &text, sizeof(&text)); printf("text+1:%p &text+1:%p \n", text+1, &text+1); return 0; } The result: sizeof(text):7 sizeof(text+2):4 sizeof(text[0]):1 text:0xbfc8769d sizeof(text):7 &text:0xbfc8769d sizeof(&text):4 text+1:0xbfc8769e &text+1:0xbfc876a4 What makes me feel confused are: why the value of 'sizeof(text)' is 7 whereas 'sizeof(text+2)' is 4 what's the difference between 'text' and '&text'?

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  • Returning pointer to a certain value in a macro?

    - by Andrei Ciobanu
    Is it possible to write a macro that has a type and a value as its input parameters (MACRO(type,value)), and returns a valid pointer to a location that holds the submitted value. This macro should perform like the following function, but in a more generic manner: int *val_to_ptr(int val){ int *r = NULL; r = nm_malloc(sizeof(*r)); *r = val; return r; } Where nm_malloc() is a failsafe malloc. The Macro usage should be compatible with this usage: printf("%d",*MACRO(int,5)); Is it possible to achieve that ?

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  • Passing array to function with pointer loses array size information!

    - by Narek
    If I write int main() { int a[100] = {1,2,3,4,}; cout<<sizeof(a)/sizeof(a[0])<<endl; return 0; } I get 400! If I write void func(int *a); int main() { int a[100] = {1,2,3,4,}; func(a); return 0; } void func(int *a) { cout<<sizeof(a)/sizeof(a[0])<<endl; } Then I get 400! So why passing array to function with pointer loses array size information?

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  • Is it possible to reinterpret pointer as dimensioned array reference?

    - by aaa
    hi. Suppose I have some pointer, which I want to reinterpret as static dimension array reference: double *p; double (&r)[4] = ?(p); // some construct? // clarify template< size_t N> void function(double (&a)[N]); ... double *p; function(p); // this will not work. // I would like to cast p as to make it appear as double[N] Is it possible to do so? how do I do it?

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