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• How to detect when an attribute is modified by calling reflection methods

  - by Oleg Pavliv

  I have the following class public class MyClass { private int myAttr; public void setAttr(int a) { myAttr = a; Thread.dumpStack(); } } That way I can detect any attempt to modify myAttr. Well, almost any. It does not work when someone modifies myAttr using Field.set() method. How can I trap Java reflection usage?

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• changing a table to array

  - by LIX

  I have a temp table which I fill and clear it in a loop in my code. becouse of using database, it takes musch time. I want to change it to an array to run my app quicker. here is my table columns: ID ( int) , Type (string ), Amount (int) may anyone help me?

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• SQL Server - Get Inserted Record Identity Value when Using a View's Instead Of Trigger

  - by CuppM

  For several tables that have identity fields, we are implementing a Row Level Security scheme using Views and Instead Of triggers on those views. Here is a simplified example structure: -- Table CREATE TABLE tblItem ( ItemId int identity(1,1) primary key, Name varchar(20) ) go -- View CREATE VIEW vwItem AS SELECT * FROM tblItem -- RLS Filtering Condition go -- Instead Of Insert Trigger CREATE TRIGGER IO_vwItem_Insert ON vwItem INSTEAD OF INSERT AS BEGIN -- RLS Security Checks on inserted Table -- Insert Records Into Table INSERT INTO tblItem (Name) SELECT Name FROM inserted; END go If I want to insert a record and get its identity, before implementing the RLS Instead Of trigger, I used: DECLARE @ItemId int; INSERT INTO tblItem (Name) VALUES ('MyName'); SELECT @ItemId = SCOPE_IDENTITY(); With the trigger, SCOPE_IDENTITY() no longer works - it returns NULL. I've seen suggestions for using the OUTPUT clause to get the identity back, but I can't seem to get it to work the way I need it to. If I put the OUTPUT clause on the view insert, nothing is ever entered into it. -- Nothing is added to @ItemIds DECLARE @ItemIds TABLE (ItemId int); INSERT INTO vwItem (Name) OUTPUT INSERTED.ItemId INTO @ItemIds VALUES ('MyName'); If I put the OUTPUT clause in the trigger on the INSERT statement, the trigger returns the table (I can view it from SQL Management Studio). I can't seem to capture it in the calling code; either by using an OUTPUT clause on that call or using a SELECT * FROM (). -- Modified Instead Of Insert Trigger w/ Output CREATE TRIGGER IO_vwItem_Insert ON vwItem INSTEAD OF INSERT AS BEGIN -- RLS Security Checks on inserted Table -- Insert Records Into Table INSERT INTO tblItem (Name) OUTPUT INSERTED.ItemId SELECT Name FROM inserted; END go -- Calling Code INSERT INTO vwItem (Name) VALUES ('MyName'); The only thing I can think of is to use the IDENT_CURRENT() function. Since that doesn't operate in the current scope, there's an issue of concurrent users inserting at the same time and messing it up. If the entire operation is wrapped in a transaction, would that prevent the concurrency issue? BEGIN TRANSACTION DECLARE @ItemId int; INSERT INTO tblItem (Name) VALUES ('MyName'); SELECT @ItemId = IDENT_CURRENT('tblItem'); COMMIT TRANSACTION Does anyone have any suggestions on how to do this better? I know people out there who will read this and say "Triggers are EVIL, don't use them!" While I appreciate your convictions, please don't offer that "suggestion".

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• help with generating models from database for many to many in doctrine

  - by ajsie

  im using doctrine and i have set up some test tables to be generated into models: I want a many-to-many relationship models (3 tables converted into 3 models) (things are simplified to make the point clear) mysql tables: user: id INT // primary key name VARCHAR group: id INT // primary key name VARCHAR user_group: user_id INT // primary and foreign key to user.id group_id INT // primary and foreign key to group.id i thought that it would generate these models (from the documentation): // User.php class User extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('id'); $this->hasColumn('name); } public function setUp() { $this->hasMany('Group as Groups', array( 'refClass' => 'UserGroup', 'local' => 'user_id', 'foreign' => 'group_id' ) ); } } // Group.php class Group extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('id'); $this->hasColumn('name); } public function setUp() { $this->hasMany('User as Users', array( 'refClass' => 'UserGroup', 'local' => 'group_id', 'foreign' => 'user_id' ) ); } } // UserGroup.php class UserGroup extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('user_id') ); $this->hasColumn('group_id') ); } } but it generated this: // User.php abstract class BaseUser extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('id'); $this->hasColumn('name'); } public function setUp() { $this->hasMany('UserGroup', array( 'local' => 'id', 'foreign' => 'user_id')); } } // Group.php abstract class BaseGroup extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('id'); $this->hasColumn('name'); } public function setUp() { $this->hasMany('UserGroup', array( 'local' => 'id', 'foreign' => 'group_id')); } } // UserGroup.php abstract class BaseUserGroup extends Doctrine_Record { public function setTableDefinition() { $this->hasColumn('user_id'); $this->hasColumn('group_id'); } public function setUp() { $this->hasOne('User', array( 'local' => 'user_id', 'foreign' => 'id')); $this->hasOne('Group', array( 'local' => 'group_id', 'foreign' => 'id')); } } as you can see, there is no 'refClass' in the 'User' and 'Group' models pointing to the 'UserGroup'. the 'UserGroup' table in this case is just another table from Doctrine's perspective not a reference table. I've checked my table definitions in mysql. They are correct. user_group has 2 columns (primary keys and foreign keys), each one pointing to the primary key in either User or Group. But i want the standard many-to-many relationship models in Doctrine models. I'd appreciate some help. I have struggled to figure it out for a half day now. What is wrong? Thanks!

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• B-trees, databases, sequential inputs, and speed.

  - by IanC

  I know from experience that b-trees have awful performance when data is added to them sequentially (regardless of the direction). However, when data is added randomly, best performance is obtained. This is easy to demonstrate with the likes of an RB-Tree. Sequential writes cause a maximum number of tree balances to be performed. I know very few databases use binary trees, but rather used n-order balanced trees. I logically assume they suffer a similar fate to binary trees when it comes to sequential inputs. This sparked my curiosity. If this is so, then one could deduce that writing sequential IDs (such as in IDENTITY(1,1)) would cause multiple re-balances of the tree to occur. I have seen many posts argue against GUIDs as "these will cause random writes". I never use GUIDs, but it struck me that this "bad" point was in fact a good point. So I decided to test it. Here is my code: SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[T1]( [ID] [int] NOT NULL CONSTRAINT [T1_1] PRIMARY KEY CLUSTERED ([ID] ASC) ) GO CREATE TABLE [dbo].[T2]( [ID] [uniqueidentifier] NOT NULL CONSTRAINT [T2_1] PRIMARY KEY CLUSTERED ([ID] ASC) ) GO declare @i int, @t1 datetime, @t2 datetime, @t3 datetime, @c char(300) set @t1 = GETDATE() set @i = 1 while @i < 2000 begin insert into T2 values (NEWID(), @c) set @i = @i + 1 end set @t2 = GETDATE() WAITFOR delay '0:0:10' set @t3 = GETDATE() set @i = 1 while @i < 2000 begin insert into T1 values (@i, @c) set @i = @i + 1 end select DATEDIFF(ms, @t1, @t2) AS [Int], DATEDIFF(ms, @t3, getdate()) AS [GUID] drop table T1 drop table T2 Note that I am not subtracting any time for the creation of the GUID nor for the considerably extra size of the row. The results on my machine were as follows: Int: 17,340 ms GUID: 6,746 ms This means that in this test, random inserts of 16 bytes was almost 3 times faster than sequential inserts of 4 bytes. Would anyone like to comment on this? Ps. I get that this isn't a question. It's an invite to discussion, and that is relevant to learning optimum programming.

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• What does the C standard say about pointers to structs and their first member?

  - by James Morris

  Consider the following two struct: struct a { int a; }; struct b { struct a a_struct; int b; }; the following instantiation of struct b: struct b b_struct; and this condition: if (&b_struct == (struct b*)&b_struct.a_struct) printf("Yes\n"); Does the C standard mandate this to always evaluate true?

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• getting Cannot identify image file when trying to create thumbnail in django

  - by Mo J. Mughrabi

  Am trying to create a thumbnail in django, am trying to build a custom class specifically to be used for generating thumbnails. As following from StringIO import StringIO from PIL import Image class Thumbnail(object): source = '' size = (50, 50) output = '' def __init__(self): pass @staticmethod def load(src): self = Thumbnail() self.source = src return self def generate(self, size=(50, 50)): if not isinstance(size, tuple): raise Exception('Thumbnail class: The size parameter must be an instance of a tuple.') self.size = size # resize properties box = self.size factor = 1 fit = True image = Image.open(self.source) # Convert to RGB if necessary if image.mode not in ('L', 'RGB'): image = image.convert('RGB') while image.size[0]/factor > 2*box[0] and image.size[1]*2/factor > 2*box[1]: factor *=2 if factor > 1: image.thumbnail((image.size[0]/factor, image.size[1]/factor), Image.NEAREST) #calculate the cropping box and get the cropped part if fit: x1 = y1 = 0 x2, y2 = image.size wRatio = 1.0 * x2/box[0] hRatio = 1.0 * y2/box[1] if hRatio > wRatio: y1 = int(y2/2-box[1]*wRatio/2) y2 = int(y2/2+box[1]*wRatio/2) else: x1 = int(x2/2-box[0]*hRatio/2) x2 = int(x2/2+box[0]*hRatio/2) image = image.crop((x1,y1,x2,y2)) #Resize the image with best quality algorithm ANTI-ALIAS image.thumbnail(box, Image.ANTIALIAS) # save image to memory temp_handle = StringIO() image.save(temp_handle, 'png') temp_handle.seek(0) self.output = temp_handle return self def get_output(self): return self.output.read() the purpose of the class is so i can use it inside different locations to generate thumbnails on the fly. The class works perfectly, I've tested it directly under a view.. I've implemented the thumbnail class inside the save method of the forms to resize the original images on saving. in my design, I have two fields for thumbnails. I was able to generate one thumbnail, if I try to generate two it crashes and I've been stuck for hours not sure whats the problem. Here is my model class Image(models.Model): article = models.ForeignKey(Article) title = models.CharField(max_length=100, null=True, blank=True) src = models.ImageField(upload_to='publication/image/') r128 = models.ImageField(upload_to='publication/image/128/', blank=True, null=True) r200 = models.ImageField(upload_to='publication/image/200/', blank=True, null=True) uploaded_at = models.DateTimeField(auto_now=True) Here is my forms class ImageForm(models.ModelForm): """ """ class Meta: model = Image fields = ('src',) def save(self, commit=True): instance = super(ImageForm, self).save(commit=True) file = Thumbnail.load(instance.src) instance.r128 = SimpleUploadedFile( instance.src.name, file.generate((128, 128)).get_output(), content_type='image/png' ) instance.r200 = SimpleUploadedFile( instance.src.name, file.generate((200, 200)).get_output(), content_type='image/png' ) if commit: instance.save() return instance the strange part is, when i remove the line which contains instance.r200 in the form save. It works fine, and it does the thumbnail and stores it successfully. Once I add the second thumbnail it fails.. Any ideas what am doing wrong here? Thanks Update: I tried earlier doing the following but I still got the same error class ImageForm(models.ModelForm): """ """ class Meta: model = Image fields = ('src',) def save(self, commit=True): instance = super(ImageForm, self).save(commit=True) instance.r128 = SimpleUploadedFile( instance.src.name, Thumbnail.load(instance.src).generate((128, 128)).get_output(), content_type='image/png' ) instance.r200 = SimpleUploadedFile( instance.src.name, Thumbnail.load(instance.src).generate((200, 200)).get_output(), content_type='image/png' ) if commit: instance.save() return instance

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• C# coding standards for private member variables [closed]

  - by Sasha

  I saw two common approaches for coding standards for private member variables: class Foo { private int _i; private string _id; } and class Foo { private int m_i; private string m_id; } I believe the latter is coming from C++. Also, many people specify type before the member variable: double m_dVal -- to indicate that is is a nonconstant member variable of the type double? What are the conventions in C#?

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• Run-Time Check Failure #2 - Stack around the variable 'indices' was corrupted.

  - by numerical25

  well I think I know what the problem is. I am just having a hard time debugging it. I am working with the directx api and I am trying to generate a plane along the x and z axis according to a book I have. The problem is when I am creating my indices. I think I am setting values out of the bounds of the indices array. I am just having a hard time figuring out what I did wrong. I am unfamiliar with the this method of generating a plane. so its a little difficult for me. below is my code. Take emphasis on the indices loop. #include "MyGame.h" //#include "CubeVector.h" /* This code sets a projection and shows a turning cube. What has been added is the project, rotation and a rasterizer to change the rasterization of the cube. The issue that was going on was something with the effect file which was causing the vertices not to be rendered correctly.*/ typedef struct { ID3D10Effect* pEffect; ID3D10EffectTechnique* pTechnique; //vertex information ID3D10Buffer* pVertexBuffer; ID3D10Buffer* pIndicesBuffer; ID3D10InputLayout* pVertexLayout; UINT numVertices; UINT numIndices; }ModelObject; ModelObject modelObject; // World Matrix D3DXMATRIX WorldMatrix; // View Matrix D3DXMATRIX ViewMatrix; // Projection Matrix D3DXMATRIX ProjectionMatrix; ID3D10EffectMatrixVariable* pProjectionMatrixVariable = NULL; //grid information #define NUM_COLS 16 #define NUM_ROWS 16 #define CELL_WIDTH 32 #define CELL_HEIGHT 32 #define NUM_VERTSX (NUM_COLS + 1) #define NUM_VERTSY (NUM_ROWS + 1) bool MyGame::InitDirect3D() { if(!DX3dApp::InitDirect3D()) { return false; } D3D10_RASTERIZER_DESC rastDesc; rastDesc.FillMode = D3D10_FILL_WIREFRAME; rastDesc.CullMode = D3D10_CULL_FRONT; rastDesc.FrontCounterClockwise = true; rastDesc.DepthBias = false; rastDesc.DepthBiasClamp = 0; rastDesc.SlopeScaledDepthBias = 0; rastDesc.DepthClipEnable = false; rastDesc.ScissorEnable = false; rastDesc.MultisampleEnable = false; rastDesc.AntialiasedLineEnable = false; ID3D10RasterizerState *g_pRasterizerState; mpD3DDevice->CreateRasterizerState(&rastDesc, &g_pRasterizerState); mpD3DDevice->RSSetState(g_pRasterizerState); // Set up the World Matrix D3DXMatrixIdentity(&WorldMatrix); D3DXMatrixLookAtLH(&ViewMatrix, new D3DXVECTOR3(0.0f, 10.0f, -20.0f), new D3DXVECTOR3(0.0f, 0.0f, 0.0f), new D3DXVECTOR3(0.0f, 1.0f, 0.0f)); // Set up the projection matrix D3DXMatrixPerspectiveFovLH(&ProjectionMatrix, (float)D3DX_PI * 0.5f, (float)mWidth/(float)mHeight, 0.1f, 100.0f); if(!CreateObject()) { return false; } return true; } //These are actions that take place after the clearing of the buffer and before the present void MyGame::GameDraw() { static float rotationAngle = 0.0f; // create the rotation matrix using the rotation angle D3DXMatrixRotationY(&WorldMatrix, rotationAngle); rotationAngle += (float)D3DX_PI * 0.0f; // Set the input layout mpD3DDevice->IASetInputLayout(modelObject.pVertexLayout); // Set vertex buffer UINT stride = sizeof(VertexPos); UINT offset = 0; mpD3DDevice->IASetVertexBuffers(0, 1, &modelObject.pVertexBuffer, &stride, &offset); mpD3DDevice->IASetIndexBuffer(modelObject.pIndicesBuffer, DXGI_FORMAT_R32_UINT, 0); // Set primitive topology mpD3DDevice->IASetPrimitiveTopology(D3D10_PRIMITIVE_TOPOLOGY_TRIANGLELIST); // Combine and send the final matrix to the shader D3DXMATRIX finalMatrix = (WorldMatrix * ViewMatrix * ProjectionMatrix); pProjectionMatrixVariable->SetMatrix((float*)&finalMatrix); // make sure modelObject is valid // Render a model object D3D10_TECHNIQUE_DESC techniqueDescription; modelObject.pTechnique->GetDesc(&techniqueDescription); // Loop through the technique passes for(UINT p=0; p < techniqueDescription.Passes; ++p) { modelObject.pTechnique->GetPassByIndex(p)->Apply(0); // draw the cube using all 36 vertices and 12 triangles mpD3DDevice->DrawIndexed(modelObject.numIndices,0,0); } } //Render actually incapsulates Gamedraw, so you can call data before you actually clear the buffer or after you //present data void MyGame::Render() { DX3dApp::Render(); } bool MyGame::CreateObject() { VertexPos vertices[NUM_VERTSX * NUM_VERTSY]; for(int z=0; z < NUM_VERTSY; ++z) { for(int x = 0; x < NUM_VERTSX; ++x) { vertices[x + z * NUM_VERTSX].pos.x = (float)x * CELL_WIDTH; vertices[x + z * NUM_VERTSX].pos.z = (float)z * CELL_HEIGHT; vertices[x + z * NUM_VERTSX].pos.y = 0.0f; vertices[x + z * NUM_VERTSX].color = D3DXVECTOR4(1.0, 0.0f, 0.0f, 0.0f); } } DWORD indices[NUM_VERTSX * NUM_VERTSY]; int curIndex = 0; for(int z=0; z < NUM_ROWS; ++z) { for(int x = 0; x < NUM_COLS; ++x) { int curVertex = x + (z * NUM_VERTSX); indices[curIndex] = curVertex; indices[curIndex + 1] = curVertex + NUM_VERTSX; indices[curIndex + 2] = curVertex + 1; indices[curIndex + 3] = curVertex + 1; indices[curIndex + 4] = curVertex + NUM_VERTSX; indices[curIndex + 5] = curVertex + NUM_VERTSX + 1; curIndex += 6; } } //Create Layout D3D10_INPUT_ELEMENT_DESC layout[] = { {"POSITION",0,DXGI_FORMAT_R32G32B32_FLOAT, 0 , 0, D3D10_INPUT_PER_VERTEX_DATA, 0}, {"COLOR",0,DXGI_FORMAT_R32G32B32A32_FLOAT, 0 , 12, D3D10_INPUT_PER_VERTEX_DATA, 0} }; UINT numElements = (sizeof(layout)/sizeof(layout[0])); modelObject.numVertices = sizeof(vertices)/sizeof(VertexPos); //Create buffer desc D3D10_BUFFER_DESC bufferDesc; bufferDesc.Usage = D3D10_USAGE_DEFAULT; bufferDesc.ByteWidth = sizeof(VertexPos) * modelObject.numVertices; bufferDesc.BindFlags = D3D10_BIND_VERTEX_BUFFER; bufferDesc.CPUAccessFlags = 0; bufferDesc.MiscFlags = 0; D3D10_SUBRESOURCE_DATA initData; initData.pSysMem = vertices; //Create the buffer HRESULT hr = mpD3DDevice->CreateBuffer(&bufferDesc, &initData, &modelObject.pVertexBuffer); if(FAILED(hr)) return false; modelObject.numIndices = sizeof(indices)/sizeof(DWORD); bufferDesc.ByteWidth = sizeof(DWORD) * modelObject.numIndices; bufferDesc.BindFlags = D3D10_BIND_INDEX_BUFFER; initData.pSysMem = indices; hr = mpD3DDevice->CreateBuffer(&bufferDesc, &initData, &modelObject.pIndicesBuffer); if(FAILED(hr)) return false; ///////////////////////////////////////////////////////////////////////////// //Set up fx files LPCWSTR effectFilename = L"effect.fx"; modelObject.pEffect = NULL; hr = D3DX10CreateEffectFromFile(effectFilename, NULL, NULL, "fx_4_0", D3D10_SHADER_ENABLE_STRICTNESS, 0, mpD3DDevice, NULL, NULL, &modelObject.pEffect, NULL, NULL); if(FAILED(hr)) return false; pProjectionMatrixVariable = modelObject.pEffect->GetVariableByName("Projection")->AsMatrix(); //Dont sweat the technique. Get it! LPCSTR effectTechniqueName = "Render"; modelObject.pTechnique = modelObject.pEffect->GetTechniqueByName(effectTechniqueName); if(modelObject.pTechnique == NULL) return false; //Create Vertex layout D3D10_PASS_DESC passDesc; modelObject.pTechnique->GetPassByIndex(0)->GetDesc(&passDesc); hr = mpD3DDevice->CreateInputLayout(layout, numElements, passDesc.pIAInputSignature, passDesc.IAInputSignatureSize, &modelObject.pVertexLayout); if(FAILED(hr)) return false; return true; }

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• Problem with pointers and getstring function

  - by volting

  I am trying to write a function to get a string from the uart1. Its for an embedded system so I don't want to use malloc. The pointer that is passed to the getstring function seems to point to garbage after the gets_e_uart1() is called. I don't use pointers too often so I'm sure it is something really stupid and trivial that Im doing wrong. Regards, V int main() { char *ptr = 0; while(1) { gets_e_uart1(ptr, 100); puts_uart1(ptr); } return 0; }*end main*/ //------------------------------------------------------------------------- //gets a string and echos it //returns 0 if there is no error char getstring_e_uart1(char *stringPtr_, const int SIZE_) { char buffer_[SIZE_]; stringPtr_ = buffer_; int start_ = 0, end_ = SIZE_ - 1; char errorflag = 0; /*keep geting chars until newline char recieved*/ while((buffer_[start_++] = getchar_uart1())!= 0x0D) { putchar_uart1(buffer_[start_]);//echo it /*check for end of buffer wraparound if neccesary*/ if(start_ == end_) { start_ = 0; errorflag = 1; } } putchar_uart1('\n'); putchar_uart1('\r'); /*check for end of buffer wraparound if neccesary*/ if(start_ == end_) { buffer_[0] = '\0'; errorflag = 1; } else { buffer_[start_++] = '\0'; } return errorflag; } Update: I decided to go with approach of passing a pointer an array to the function. This works nicely, thanks to everyone for the informative answers. Updated Code: //------------------------------------------------------------------------- //argument 1 should be a pointer to an array, //and the second argument should be the size of the array //gets a string and echos it //returns 0 if there is no error char getstring_e_uart1(char *stringPtr_, const int SIZE_) { char *startPtr_ = stringPtr_; char *endPtr_ = startPtr_ + (SIZE_ - 1); char errorflag = 0; /*keep geting chars until newline char recieved*/ while((*stringPtr_ = getchar_uart1())!= 0x0D) { putchar_uart1(*stringPtr_);//echo it stringPtr_++; /*check for end of buffer wraparound if neccesary*/ if(stringPtr_ == endPtr_) { stringPtr_ = startPtr_; errorflag = 1; } } putchar_uart1('\n'); putchar_uart1('\r'); /*check for end of buffer wraparound if neccesary*/ if(stringPtr_ == endPtr_) { stringPtr_ = startPtr_; *stringPtr_ = '\0'; errorflag = 1; } else { *stringPtr_ = '\0'; } return errorflag; }

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• gets (variable)

  - by borlee

  can anyone tell me why gets(abc) works with char[] but not with int? int abc; char name[] = "lolrofl"; printf("Hello %s.\n",name); printf("\n "); fflush(stdin); gets (abc); printf("\n die zahl ist %i.\n",abc); system("Pause"); return(0);

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• KeyNotFound Exception in Dictionary(of T)

  - by C Patton

  I'm about ready to bang my head against the wall I have a class called Map which has a dictionary called tiles. class Map { public Dictionary<Location, Tile> tiles = new Dictionary<Location, Tile>(); public Size mapSize; public Map(Size size) { this.mapSize = size; } //etc... I fill this dictionary temporarily to test some things.. public void FillTemp(Dictionary<int, Item> itemInfo) { Random r = new Random(); for(int i =0; i < mapSize.Width; i++) { for(int j=0; j<mapSize.Height; j++) { Location temp = new Location(i, j, 0); int rint = r.Next(0, (itemInfo.Count - 1)); Tile t = new Tile(new Item(rint, rint)); tiles[temp] = t; } } } and in my main program code Map m = new Map(10, 10); m.FillTemp(iInfo); Tile t = m.GetTile(new Location(2, 2, 0)); //The problem line now, if I add a breakpoint in my code, I can clearly see that my instance (m) of the map class is filled with pairs via the function above, but when I try to access a value with the GetTile function: public Tile GetTile(Location location) { if(this.tiles.ContainsKey(location)) { return this.tiles[location]; } else { return null; } } it ALWAYS returns null. Again, if I view inside the Map object and find the Location key where x=2,y=2,z=0 , I clearly see the value being a Tile that FillTemp generated.. Why is it doing this? I've had no problems with a Dictionary such as this so far. I have no idea why it's returning null. and again, when debugging, I can CLEARLY see that the Map instance contains the Location key it says it does not... very frustrating. Any clues? Need any more info? Help would be greatly appreciated :)

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• Visual Studio keyboard short-cut to complete default accessors {get; set;}

  - by Zamboni

  I am looking for a keyboard short-cut to complete creating the default accessors for a property in a C# class. Something like... I start typing: public int Id Then I press one or more keys, and I endup with: public int Id { get; set; }

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• what should the output of a lexer be in c?

  - by mekasperasky

  #include<stdio.h> int main() { int a,b; a=a+b; printf("%d",a); return 0; } what should be the output if this code is passed through a lexer

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• Poor performance / speed of regex with lookahead

  - by Hugo Zaragoza

  I have been observing extremely slow execution times with expressions with several lookaheads. I suppose that this is due to underlying data structures, but it seems pretty extreme and I wonder if I do something wrong or if there are known work-arounds. The problem is determining if a set of words are present in a string, in any order. For example we want to find out if two terms "term1" AND "term2" are somewhere in a string. I do this with the expresion: (?=.*\bterm1\b)(?=.*\bterm2\b) But what I observe is that this is an order of magnitude slower than checking first just \bterm1\b and just then \bterm2\b This seems to indicate that I should use an array of patterns instead of a single pattern with lookaheads... is this right? it seems wrong... Here is an example test code and resulting times: public static void speedLookAhead() { Matcher m, m1, m2; boolean find; int its = 1000000; // create long non-matching string char[] str = new char[2000]; for (int i = 0; i < str.length; i++) { str[i] = 'x'; } String test = str.toString(); // First method: use one expression with lookaheads m = Pattern.compile("(?=.*\\bterm1\\b)(?=.*\\bterm2\\b)").matcher(test); long time = System.currentTimeMillis(); ; for (int i = 0; i < its; i++) { m.reset(test); find = m.find(); } time = System.currentTimeMillis() - time; System.out.println(time); // Second method: use two expressions and AND the results m1 = Pattern.compile("\\bterm1\\b").matcher(test); m2 = Pattern.compile("\\bterm2\\b").matcher(test); time = System.currentTimeMillis(); ; for (int i = 0; i < its; i++) { m1.reset(test); m2.reset(test); find = m1.find() && m2.find(); } time = System.currentTimeMillis() - time; System.out.println(time); } This outputs in my computer: 1754 150

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• How to initialize all elements in an array to the same number in C++

  - by Phenom

  I'm trying to initialize an int array with everything set at -1. I tried the following, but it doesn't work. It only sets the first value at -1. int directory[100] = {-1}; Why doesn't it work right?

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• C: reading file and populating struct

  - by deostroll

  Hi, I have a structure with the following definition: typedef struct myStruct{ int a; char* c; int f; } OBJECT; I am able to populate this object and write it to a file. However I am not able to read the char* c value in it...while trying to read it, it gives me a segmentation fault error. Is there anything wrong with my code: //writensave.c #include "mystruct.h" #include <stdio.h> #include <string.h> #define p(x) printf(x) int main() { p("Creating file to write...\n"); FILE* file = fopen("struct.dat", "w"); if(file == NULL) { printf("Error opening file\n"); return -1; } p("creating structure\n"); OBJECT* myObj = (OBJECT*)malloc(sizeof(OBJECT)); myObj->a = 20; myObj->f = 45; myObj->c = (char*)calloc(30, sizeof(char)); strcpy(myObj->c, "This is a test"); p("Writing object to file...\n"); fwrite(myObj, sizeof(OBJECT), 1, file); p("Close file\n"); fclose(file); p("End of program\n"); return 0; } Here is how I am trying to read it: //readnprint.c #include "mystruct.h" #include <stdio.h> #define p(x) printf(x) int main() { FILE* file = fopen("struct.dat", "r"); char* buffer; buffer = (char*) malloc(sizeof(OBJECT)); if(file == NULL) { p("Error opening file"); return -1; } fread((void *)buffer, sizeof(OBJECT), 1, file); OBJECT* obj = (OBJECT*)buffer; printf("obj->a = %d\nobj->f = %d \nobj->c = %s", obj->a, obj->f, obj->c); fclose(file); return 0; }

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• Multiply char by integer (c++)

  - by dubya

  Is it possible to multiply a char by an int? For example, I am trying to make a graph, with *'s for each time a number occurs. So something like, but this doesn't work char star = "*"; int num = 7; cout << star * num //to output 7 stars

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• Can MySQL reasonably perform queries on billions of rows?

  - by haxney

  I am planning on storing scans from a mass spectrometer in a MySQL database and would like to know whether storing and analyzing this amount of data is remotely feasible. I know performance varies wildly depending on the environment, but I'm looking for the rough order of magnitude: will queries take 5 days or 5 milliseconds? Input format Each input file contains a single run of the spectrometer; each run is comprised of a set of scans, and each scan has an ordered array of datapoints. There is a bit of metadata, but the majority of the file is comprised of arrays 32- or 64-bit ints or floats. Host system |----------------+-------------------------------| | OS | Windows 2008 64-bit | | MySQL version | 5.5.24 (x86_64) | | CPU | 2x Xeon E5420 (8 cores total) | | RAM | 8GB | | SSD filesystem | 500 GiB | | HDD RAID | 12 TiB | |----------------+-------------------------------| There are some other services running on the server using negligible processor time. File statistics |------------------+--------------| | number of files | ~16,000 | | total size | 1.3 TiB | | min size | 0 bytes | | max size | 12 GiB | | mean | 800 MiB | | median | 500 MiB | | total datapoints | ~200 billion | |------------------+--------------| The total number of datapoints is a very rough estimate. Proposed schema I'm planning on doing things "right" (i.e. normalizing the data like crazy) and so would have a runs table, a spectra table with a foreign key to runs, and a datapoints table with a foreign key to spectra. The 200 Billion datapoint question I am going to be analyzing across multiple spectra and possibly even multiple runs, resulting in queries which could touch millions of rows. Assuming I index everything properly (which is a topic for another question) and am not trying to shuffle hundreds of MiB across the network, is it remotely plausible for MySQL to handle this? UPDATE: additional info The scan data will be coming from files in the XML-based mzML format. The meat of this format is in the <binaryDataArrayList> elements where the data is stored. Each scan produces = 2 <binaryDataArray> elements which, taken together, form a 2-dimensional (or more) array of the form [[123.456, 234.567, ...], ...]. These data are write-once, so update performance and transaction safety are not concerns. My naïve plan for a database schema is: runs table | column name | type | |-------------+-------------| | id | PRIMARY KEY | | start_time | TIMESTAMP | | name | VARCHAR | |-------------+-------------| spectra table | column name | type | |----------------+-------------| | id | PRIMARY KEY | | name | VARCHAR | | index | INT | | spectrum_type | INT | | representation | INT | | run_id | FOREIGN KEY | |----------------+-------------| datapoints table | column name | type | |-------------+-------------| | id | PRIMARY KEY | | spectrum_id | FOREIGN KEY | | mz | DOUBLE | | num_counts | DOUBLE | | index | INT | |-------------+-------------| Is this reasonable?

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• Can you explicitly set a structure layout/alignment in C++ as you can in C#?

  - by Gary Willoughby

  In C# you have nice alignment attributes such as this: [StructLayout(LayoutKind.Explicit)] public struct Message { [FieldOffset(0)] public int a; [FieldOffset(4)] public short b; [FieldOffset(6)] public int c; [FieldOffset(22)] //Leave some empty space just for the heck of it. public DateTime dt; } Which gives you fine control on how you need your structure to be layed out in memory. Is there such a thing in standard C++?

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• Why ParameterInfo::GetXXXCustomModifiers does not returns IsLong if the parameter is ByRef?

  - by AZ

  Given a ParameterInfo p from this: void foo(int modopt(IsLong) n); p.GetOptionalCustomModifiers() returns a System.Runtime.CompilerServices.IsLong; however, if the method signature happens to be: void foo(out int modopt(IsLong) n); It does not. Is there a work around for this?

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• A Built-in Function to Convert from String to Byte

  - by Ngu Soon Hui

  I have the following function: public static byte[] StringToByte(string str) { int length = str.Length; byte[] ba = new byte[length]; for (int i = 0; i < length; i++) { ba[i] = (byte)str[i]; } return ba; } I wonder whether there is a built-in function for this method?

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• Cryptic C++ "thing" (function pointer)

  - by m00st

  What is this syntax for in C++? Can someone point me to the technical term so I can see if I find anything in my text? At first I thought it was a prototype but then the = and (*fn) threw me off... Here is my example: void (*fn) (int&,int&) = x;

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• multi-thread access MySQL error

  - by user188916

  I have written a simple multi-threaded C program to access MySQL,it works fine except when i add usleep() or sleep() function in each thread function. i created two pthreads in the main method, int main(){ mysql_library_init(0,NULL,NULL); printf("Hello world!\n"); init_pool(&p,100); pthread_t producer; pthread_t consumer_1; pthread_t consumer_2; pthread_create(&producer,NULL,produce_fun,NULL); pthread_create(&consumer_1,NULL,consume_fun,NULL); pthread_create(&consumer_2,NULL,consume_fun,NULL); mysql_library_end(); } void * produce_fun(void *arg){ pthread_detach(pthread_self()); //procedure while(1){ usleep(500000); printf("producer...\n"); produce(&p,cnt++); } pthread_exit(NULL); } void * consume_fun(void *arg){ pthread_detach(pthread_self()); MYSQL db; MYSQL *ptr_db=mysql_init(&db); mysql_real_connect(); //procedure while(1){ usleep(1000000); printf("consumer..."); int item=consume(&p); addRecord_d(ptr_db,"test",item); } mysql_thread_end(); pthread_exit(NULL); } void addRecord_d(MYSQL *ptr_db,const char *t_name,int item){ char query_buffer[100]; sprintf(query_buffer,"insert into %s values(0,%d)",t_name,item); //pthread_mutex_lock(&db_t_lock); int ret=mysql_query(ptr_db,query_buffer); if(ret){ fprintf(stderr,"%s%s\n","cannot add record to ",t_name); return; } unsigned long long update_id=mysql_insert_id(ptr_db); // pthread_mutex_unlock(&db_t_lock); printf("add record (%llu,%d) ok.",update_id,item); } the program output errors like: [Thread debugging using libthread_db enabled] [New Thread 0xb7ae3b70 (LWP 7712)] Hello world! [New Thread 0xb72d6b70 (LWP 7713)] [New Thread 0xb6ad5b70 (LWP 7714)] [New Thread 0xb62d4b70 (LWP 7715)] [Thread 0xb7ae3b70 (LWP 7712) exited] producer... producer... consumer...consumer...add record (31441,0) ok.add record (31442,1) ok.producer... producer... consumer...consumer...add record (31443,2) ok.add record (31444,3) ok.producer... producer... consumer...consumer...add record (31445,4) ok.add record (31446,5) ok.producer... producer... consumer...consumer...add record (31447,6) ok.add record (31448,7) ok.producer... Error in my_thread_global_end(): 2 threads didn't exit [Thread 0xb72d6b70 (LWP 7713) exited] [Thread 0xb6ad5b70 (LWP 7714) exited] [Thread 0xb62d4b70 (LWP 7715) exited] Program exited normally. and when i add pthread_mutex_lock in function addRecord_d,the error still exists. So what exactly the problem is?

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• is hashCode() must return a prime number

  - by subhashis

  The signature of the hashCode() method is public int hashCode(){ return x; } in this case x must be an int(primitive) but plz can anyone explain it to me that the number which the hashCode() returns must be a prime number, even number...etc or there is no specification ? the reason behind i am asking this question is i have seen it in different ids the auto generated code always returns a prime number, so i need to know why? thanks in advance

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