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• C++ Pointers to functions.

  - by Andy Leman

  using namespace std; int addition (int a, int b) { return (a+b); } int subtraction (int a, int b) { return (a-b); } int operation (int x, int y, int (*functocall)(int,int)) { int g; g = (*functocall)(x,y); return(g); } int main() { int m,n; int (*minus)(int,int) = subtraction; m = operation (7,5,addition); n = operation (20,m,minus); cout << n; return 0; } Can anybody explain this line for me int (*minus)(int,int) = subtraction; Thanks a lot!

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• Efficient way in Python to remove an element from a comma-separated string

  - by ensnare

  I'm looking for the most efficient way to add an element to a comma-separated string while maintaining alphabetical order for the words: For example: string = 'Apples, Bananas, Grapes, Oranges' subtraction = 'Bananas' result = 'Apples, Grapes, Oranges' Also, a way to do this but while maintaining IDs: string = '1:Apples, 4:Bananas, 6:Grapes, 23:Oranges' subtraction = '4:Bananas' result = '1:Apples, 6:Grapes, 23:Oranges' Sample code is greatly appreciated. Thank you so much.

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• Which opcodes are faster at the CPU level?

  - by Geotarget

  In every programming language there are sets of opcodes that are recommended over others. I've tried to list them here, in order of speed. Bitwise Integer Addition / Subtraction Integer Multiplication / Division Comparison Control flow Float Addition / Subtraction Float Multiplication / Division Where you need high-performance code, C++ can be hand optimized in assembly, to use SIMD instructions or more efficient control flow, data types, etc. So I'm trying to understand if the data type (int32 / float32 / float64) or the operation used (*, +, &) affects performance at the CPU level. Is a single multiply slower on the CPU than an addition? In MCU theory you learn that speed of opcodes is determined by the number of CPU cycles it takes to execute. So does it mean that multiply takes 4 cycles and add takes 2? Exactly what are the speed characteristics of the basic math and control flow opcodes? If two opcodes take the same number of cycles to execute, then both can be used interchangeably without any performance gain / loss? Any other technical details you can share regarding x86 CPU performance is appreciated

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• image processing

  - by mithila

  where i can find useful tutorials about background subtraction?what are the algorithms?

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• Why unsigned int contained negative number

  - by Daziplqa

  Hi All, I am new to C, What I know about unsigned numerics (unsigned short, int and longs), that It contains positive numbers only, but the following simple program successfully assigned a negative number to an unsigned int: 1 /* 2 * ===================================================================================== 3 * 4 * Filename: prog4.c 5 * 6 * ===================================================================================== 7 */ 8 9 #include <stdio.h> 10 11 int main(void){ 12 13 int v1 =0, v2=0; 14 unsigned int sum; 15 16 v1 = 10; 17 v2 = 20; 18 19 sum = v1 - v2; 20 21 printf("The subtraction of %i from %i is %i \n" , v1, v2, sum); 22 23 return 0; 24 } The output is : The subtraction of 10 from 20 is -10

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• makefile compilation problem

  - by mistique

  He I have a problem with a makefile. I have three classes. They do pretty simple stuff. One does an addition on a subtraction, and the last one will instantiate the two and simply print the resulted addition and subtraction. Now when I create my makefile, I compile my Plus.java and my Minus.java but don't know how to compile the main class because it depends on the previous two. I want to compile and run it from the makefile if it's possible. I get the above results when I try to run make: javac -g Plus.class Minus.class javac: invalid flag: Plus.class Usage: javac use -help for a list of possible options make: * [Operation.class] Error 2 I don't know how to procede, please forgive me if my question is to simple but I am new working with these stuff. I've searched many sites but with no answer.

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• Implementing set operations in TSQL

  - by dotneteer

  SQL excels at operating on dataset. In this post, I will discuss how to implement basic set operations in transact SQL (TSQL). The operations that I am going to discuss are union, intersection and complement (subtraction).   Union Intersection Complement (subtraction) Implementing set operations using union, intersect and except We can use TSQL keywords union, intersect and except to implement set operations. Since we are in an election year, I will use voter records of propositions as an example. We create the following table and insert 6 records into the table. declare @votes table (VoterId int, PropId int) insert into @votes values (1, 30) insert into @votes values (2, 30) insert into @votes values (3, 30) insert into @votes values (4, 30) insert into @votes values (4, 31) insert into @votes values (5, 31) Voters 1, 2, 3 and 4 voted for proposition 30 and voters 4 and 5 voted for proposition 31. The following TSQL statement implements union using the union keyword. The union returns voters who voted for either proposition 30 or 31. select VoterId from @votes where PropId = 30 union select VoterId from @votes where PropId = 31 The following TSQL statement implements intersection using the intersect keyword. The intersection will return voters who voted only for both proposition 30 and 31. select VoterId from @votes where PropId = 30 intersect select VoterId from @votes where PropId = 31 The following TSQL statement implements complement using the except keyword. The complement will return voters who voted for proposition 30 but not 31. select VoterId from @votes where PropId = 30 except select VoterId from @votes where PropId = 31 Implementing set operations using join An alternative way to implement set operation in TSQL is to use full outer join, inner join and left outer join. The following TSQL statement implements union using full outer join. select Coalesce(A.VoterId, B.VoterId) from (select VoterId from @votes where PropId = 30) A full outer join (select VoterId from @votes where PropId = 31) B on A.VoterId = B.VoterId The following TSQL statement implements intersection using inner join. select Coalesce(A.VoterId, B.VoterId) from (select VoterId from @votes where PropId = 30) A inner join (select VoterId from @votes where PropId = 31) B on A.VoterId = B.VoterId The following TSQL statement implements complement using left outer join. select Coalesce(A.VoterId, B.VoterId) from (select VoterId from @votes where PropId = 30) A left outer join (select VoterId from @votes where PropId = 31) B on A.VoterId = B.VoterId where B.VoterId is null Which one to choose? To choose which technique to use, just keep two things in mind: The union, intersect and except technique treats an entire record as a member. The join technique allows the member to be specified in the “on” clause. However, it is necessary to use Coalesce function to project sets on the two sides of the join into a single set.

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• Using multiplication and division with delta time

  - by tesselode

  Using delta time with addition and subtraction is easy. player.x += 100 * dt However, multiplication and division complicate things a bit. For example, let's say I want the player to double his speed every second. player.x = player.x * 2 * dt I can't do this because it'll slow down the player (unless delta time is really high). Division is the same way, except it'll speed things way up. How can I handle multiplication and division with delta time?

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• boolean operations on meshes

  - by lathomas64

  given a set of vertices and triangles for each mesh. Does anyone know of an algorithm, or a place to start looking( I tried google first but haven't found a good place to get started) to perform boolean operations on said meshes and get a set of vertices and triangle for the resulting mesh? Of particular interest are subtraction and union. Example pictures: http://www.rhino3d.com/4/help/Commands/Booleans.htm

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• SQL SERVER – Basic Calculation and PEMDAS Order of Operation

  - by pinaldave

  After thinking a long time, I have decided to write about this blog post. I had no plan to create a blog post about this subject but the amount of conversation this one has created on my Facebook page, I decided to bring up a few of the question and concerns discussed on the Facebook page. There are more than 10,000 comments here so far. There are lots of discussion about what should be the answer. Well, as far as I can tell there is a big debate going on on Facebook, for educational purpose you should go ahead and read some of the comments. They are very interesting and for sure teach some new stuff. Even though some of the comments are clearly wrong they have made some good points and I believe it for sure develops some logic. Here is my take on this subject. I believe the answer is 9 as I follow PEMDAS  Order of Operation. PEMDAS stands for  parentheses, exponents, multiplication, division, addition, subtraction. PEMDAS is commonly known as BODMAS in India. BODMAS stands for Brackets, Orders (ie Powers and Square Roots, etc), Division, Multiplication,  Addition and Subtraction. PEMDAS and BODMAS are almost same and both of them follow the operation order from LEFT to RIGHT. Let us try to simplify above statement using the PEMDAS or BODMAS (whatever you prefer to call). Step 1: 6 ÷ 2 (1+2) (parentheses first) Step 2: = 6 ÷ 2 * (1+2) (adding multiplication sign for further clarification) Step 3: = 6 ÷ 2* (3) (single digit in parentheses – simplify using operator) Step 4: = 6 ÷ 2 * 3 (Remember next Operation should be LEFT to RIGHT) Step 5: = 3 * 3 (because 6 ÷ 2 = 3; remember LEFT to RIGHT) Step 6: = 9 (final answer) Some often find Step 4 confusing and often ended up multiplying 2 and 3 resulting Step 5 to be 6 ÷ 6, this is incorrect because in this case we did not follow the order of LEFT to RIGHT. When we do not follow the order of operation from LEFT to RIGHT we end up with the answer 1 which is incorrect. Let us see what SQL Server returns as a result. I executed following statement in SQL Server Management Studio SELECT 6/2*(1+2) It is clear that SQL Server also thinks that the answer should be 9. Let us go ahead and ask Google what will be the answer of above question in Google I have searched for the following term: 6/2(1+2) The result also says the answer should be 9. If you want a further reference here is a great video which describes why the answer should be 9 and not 1. And here is a fantastic conversation on Google Groups. Well, now what is your take on this subject? You are welcome to share constructive feedback and your answer may be different from my answer. NOTE: A healthy conversation about this subject is indeed encouraged but if there is a single bad word or comment is flaming it will be deleted without any notification (it does not matter how valuable information it contains). Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: About Me, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Simple Java calculator

  - by Kevin Duke

  Firstly this is not a homework question. I am practicing my knowledge on java. I figured a good way to do this is to write a simple program without help. Unfortunately, my compiler is telling me errors I don't know how to fix. Without changing much logic and code, could someone kindly point out where some of my errors are? Thanks import java.lang.*; import java.util.*; public class Calculator { private int solution; private int x; private int y; private char operators; public Calculator() { solution = 0; Scanner operators = new Scanner(System.in); Scanner operands = new Scanner(System.in); } public int addition(int x, int y) { return x + y; } public int subtraction(int x, int y) { return x - y; } public int multiplication(int x, int y) { return x * y; } public int division(int x, int y) { solution = x / y; return solution; } public void main (String[] args) { System.out.println("What operation? ('+', '-', '*', '/')"); System.out.println("Insert 2 numbers to be subtracted"); System.out.println("operand 1: "); x = operands; System.out.println("operand 2: "); y = operands.next(); switch(operators) { case('+'): addition(operands); operands.next(); break; case('-'): subtraction(operands); operands.next(); break; case('*'): multiplication(operands); operands.next(); break; case('/'): division(operands); operands.next(); break; } } }

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• How do I improve my performance with this singly linked list struct within my program?

  - by Jesus

  Hey guys, I have a program that does operations of sets of strings. We have to implement functions such as addition and subtraction of two sets of strings. We are suppose to get it down to the point where performance if of O(N+M), where N,M are sets of strings. Right now, I believe my performance is at O(N*M), since I for each element of N, I go through every element of M. I'm particularly focused on getting the subtraction to the proper performance, as if I can get that down to proper performance, I believe I can carry that knowledge over to the rest of things I have to implement. The '-' operator is suppose to work like this, for example. Declare set1 to be an empty set. Declare set2 to be a set with { a b c } elements Declare set3 to be a set with ( b c d } elements set1 = set2 - set3 And now set1 is suppose to equal { a }. So basically, just remove any element from set3, that is also in set2. For the addition implementation (overloaded '+' operator), I also do the sorting of the strings (since we have to). All the functions work right now btw. So I was wondering if anyone could a) Confirm that currently I'm doing O(N*M) performance b) Give me some ideas/implementations on how to improve the performance to O(N+M) Note: I cannot add any member variables or functions to the class strSet or to the node structure. The implementation of the main program isn't very important, but I will post the code for my class definition and the implementation of the member functions: strSet2.h (Implementation of my class and struct) // Class to implement sets of strings // Implements operators for union, intersection, subtraction, // etc. for sets of strings // V1.1 15 Feb 2011 Added guard (#ifndef), deleted using namespace RCH #ifndef _STRSET_ #define _STRSET_ #include <iostream> #include <vector> #include <string> // Deleted: using namespace std; 15 Feb 2011 RCH struct node { std::string s1; node * next; }; class strSet { private: node * first; public: strSet (); // Create empty set strSet (std::string s); // Create singleton set strSet (const strSet &copy); // Copy constructor ~strSet (); // Destructor int SIZE() const; bool isMember (std::string s) const; strSet operator + (const strSet& rtSide); // Union strSet operator - (const strSet& rtSide); // Set subtraction strSet& operator = (const strSet& rtSide); // Assignment }; // End of strSet class #endif // _STRSET_ strSet2.cpp (implementation of member functions) #include <iostream> #include <vector> #include <string> #include "strset2.h" using namespace std; strSet::strSet() { first = NULL; } strSet::strSet(string s) { node *temp; temp = new node; temp->s1 = s; temp->next = NULL; first = temp; } strSet::strSet(const strSet& copy) { if(copy.first == NULL) { first = NULL; } else { node *n = copy.first; node *prev = NULL; while (n) { node *newNode = new node; newNode->s1 = n->s1; newNode->next = NULL; if (prev) { prev->next = newNode; } else { first = newNode; } prev = newNode; n = n->next; } } } strSet::~strSet() { if(first != NULL) { while(first->next != NULL) { node *nextNode = first->next; first->next = nextNode->next; delete nextNode; } } } int strSet::SIZE() const { int size = 0; node *temp = first; while(temp!=NULL) { size++; temp=temp->next; } return size; } bool strSet::isMember(string s) const { node *temp = first; while(temp != NULL) { if(temp->s1 == s) { return true; } temp = temp->next; } return false; } strSet strSet::operator + (const strSet& rtSide) { strSet newSet; newSet = *this; node *temp = rtSide.first; while(temp != NULL) { string newEle = temp->s1; if(!isMember(newEle)) { if(newSet.first==NULL) { node *newNode; newNode = new node; newNode->s1 = newEle; newNode->next = NULL; newSet.first = newNode; } else if(newSet.SIZE() == 1) { if(newEle < newSet.first->s1) { node *tempNext = newSet.first; node *newNode; newNode = new node; newNode->s1 = newEle; newNode->next = tempNext; newSet.first = newNode; } else { node *newNode; newNode = new node; newNode->s1 = newEle; newNode->next = NULL; newSet.first->next = newNode; } } else { node *prev = NULL; node *curr = newSet.first; while(curr != NULL) { if(newEle < curr->s1) { if(prev == NULL) { node *newNode; newNode = new node; newNode->s1 = newEle; newNode->next = curr; newSet.first = newNode; break; } else { node *newNode; newNode = new node; newNode->s1 = newEle; newNode->next = curr; prev->next = newNode; break; } } if(curr->next == NULL) { node *newNode; newNode = new node; newNode->s1 = newEle; newNode->next = NULL; curr->next = newNode; break; } prev = curr; curr = curr->next; } } } temp = temp->next; } return newSet; } strSet strSet::operator - (const strSet& rtSide) { strSet newSet; newSet = *this; node *temp = rtSide.first; while(temp != NULL) { string element = temp->s1; node *prev = NULL; node *curr = newSet.first; while(curr != NULL) { if( element < curr->s1 ) break; if( curr->s1 == element ) { if( prev == NULL) { node *duplicate = curr; newSet.first = newSet.first->next; delete duplicate; break; } else { node *duplicate = curr; prev->next = curr->next; delete duplicate; break; } } prev = curr; curr = curr->next; } temp = temp->next; } return newSet; } strSet& strSet::operator = (const strSet& rtSide) { if(this != &rtSide) { if(first != NULL) { while(first->next != NULL) { node *nextNode = first->next; first->next = nextNode->next; delete nextNode; } } if(rtSide.first == NULL) { first = NULL; } else { node *n = rtSide.first; node *prev = NULL; while (n) { node *newNode = new node; newNode->s1 = n->s1; newNode->next = NULL; if (prev) { prev->next = newNode; } else { first = newNode; } prev = newNode; n = n->next; } } } return *this; }

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• Delphi: How to avoid EIntOverflow underflow when subtracting?

  - by Ian Boyd

  Microsoft already says, in the documentation for GetTickCount, that you could never compare tick counts to check if an interval has passed. e.g.: Incorrect (pseudo-code): DWORD endTime = GetTickCount + 10000; //10 s from now ... if (GetTickCount > endTime) break; The above code is bad because it is suceptable to rollover of the tick counter. For example, assume that the clock is near the end of it's range: endTime = 0xfffffe00 + 10000 = 0x00002510; //9,488 decimal Then you perform your check: if (GetTickCount > endTime) Which is satisfied immediatly, since GetTickCount is larger than endTime: if (0xfffffe01 > 0x00002510) The solution Instead you should always subtract the two time intervals: DWORD startTime = GetTickCount; ... if (GetTickCount - startTime) > 10000 //if it's been 10 seconds break; Looking at the same math: if (GetTickCount - startTime) > 10000 if (0xfffffe01 - 0xfffffe00) > 10000 if (1 > 10000) Which is all well and good in C/C++, where the compiler behaves a certain way. But what about Delphi? But when i perform the same math in Delphi, with overflow checking on ({Q+}, {$OVERFLOWCHECKS ON}), the subtraction of the two tick counts generates an EIntOverflow exception when the TickCount rolls over: if (0x00000100 - 0xffffff00) > 10000 0x00000100 - 0xffffff00 = 0x00000200 What is the intended solution for this problem? Edit: i've tried to temporarily turn off OVERFLOWCHECKS: {$OVERFLOWCHECKS OFF}] delta = GetTickCount - startTime; {$OVERFLOWCHECKS ON} But the subtraction still throws an EIntOverflow exception. Is there a better solution, involving casts and larger intermediate variable types?

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• How can I compare the performance of log() and fp division in C++?

  - by Ventzi Zhechev

  Hi, I’m using a log-based class in C++ to store very small floating-point values (as the values otherwise go beyond the scope of double). As I’m performing a large number of multiplications, this has the added benefit of converting the multiplications to sums. However, at a certain point in my algorithm, I need to divide a standard double value by an integer value and than do a *= to a log-based value. I have overloaded the *= operator for my log-based class and the right-hand side value is first converted to a log-based value by running log() and than added to the left-hand side value. Thus the operations actually performed are floating-point division, log() and floating-point summation. My question whether it would be faster to first convert the denominator to a log-based value, which would replace the floating-point division with floating-point subtraction, yielding the following chain of operations: twice log(), floating-point subtraction, floating-point summation. In the end, this boils down to whether floating-point division is faster or slower than log(). I suspect that a common answer would be that this is compiler and architecture dependent, so I’ll say that I use gcc 4.2 from Apple on darwin 10.3.0. Still, I hope to get an answer with a general remark on the speed of these two operators and/or an idea on how to measure the difference myself, as there might be more going on here, e.g. executing the constructors that do the type conversion etc. Cheers!

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• Can basic mathematics be done in Microsoft Word?

  - by Christopher Chipps

  Is there a function of MS Word that enables users to solve basic math problems, in this case addition or subtraction? I use its platform for a budget and of course I could just use a calculator but it would be more convenient if I could solve it all in one place. For instance: (6.75 + 12.65 + 27.35) Sorry for the simplicity of this question. Wondering if MS Word had a functionality like this of some sort?

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• A Quantity class with units

  - by Ryan Ohs

  Goals Create a class that associates a numeric quantity with a unit of measurement. Provide support for simple arithmetic and comparison operations. Implementation An immutable class (Could have been struct but I may try inheritance later) Unit is stored in an enumeration Supported operations: Addition w/ like units Subtraction w/ like units Multiplication by scalar Division by scalar Modulus by scalar Equals() >, >=, <, <=, == IComparable ToString() Implicit cast to Decimal The Source The souce can be downloaded from Github. Notes This class does not support any arithmetic that would modify the unit. This class is not suitable for manipulating currencies. Future Ideas Have a CompositeQuantity class that would allow quantities with unlike units to be combined. Similar currency class with support for allocations/distributions. Provide conversion between units. (Actually I think this would be best placed in an external service. Many situations I deal with require some sort of dynamic conversion ratio.)

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• 2D tower defense - A bullet to an enemy

  - by Tashu

  I'm trying to find a good solution for a bullet to hit the enemy. The game is 2D tower defense, the tower is supposed to shoot a bullet and hit the enemy guaranteed. I tried this solution - http://blog.wolfire.com/2009/07/linear-algebra-for-game-developers-part-1/ The link mentioned to subtract the bullet's origin and the enemy as well (vector subtraction). I tried that but a bullet just follows around the enemy. float diffX = enemy.position.x - position.x; float diffY = enemy.position.y - position.y; velocity.x = diffX; velocity.y = diffY; position.add(velocity.x * deltaTime, velocity.y * deltaTime); I'm familiar with vectors but not sure what steps (vector math operations) to be done to get this solution working.

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• Windows Azure HPC Scheduler Architecture

  - by Churianov Roman

  So far I've found very little information on the scheduling policy, resource management policy of Azure HPC Scheduler. I would appreciate any kind of information regarding some of these questions: What scheduling policy does a Head Node use to scatter jobs to Compute Nodes? Does Azure Scheduler use prior information about the jobs (compute time, memory demands ...) ? If 'yes', how it gets this information? Does Azure Scheduler split a job into several parallel jobs on one Compute node? Does it have any protection from Compute Node failures? (what it does when a compute node stops responding) Does it support addition/subtraction of Compute nodes? Is it possible to cancel a job? P.S. I'm aware of the MSDN resource Windows Azure HPC Scheduler. I found only information of how to use this Scheduler but almost nothing about how it works inside.

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• Create many similar classes, or just one

  - by soandos

  The goal is to create an application that has objects that can represent some operations (add, subtract, etc). All of those objects will have common functions and members, and thus will either implement an interface or inherit from an abstract class (Which would be better practice, this will be in C# if that matters?). As far as I can see, there are two different ways of organizing all of these classes. I could create an addition class, a subtraction class, etc. This has the upside of being highly modular but the difference between classes is so minimal. I could create one class, and have a member that will say what type of operation is being represented. This means lots of switch statements, and losing some modularity, in addition to being harder to maintain. Which is is better practice? Is there a better way of doing that is not listed above? If it matters, the list of functions that should be supported is long.

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• Create a class MAT of size m x n

  - by simret

  Create a class MAT of size m x n. Define the following matrix operations for MAT type objects a. Addition b. Subtraction c. Multiplication.

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• date_sub is not working

  - by TIT

  As my server is not upgreaded to php 5.3 (it is in PHP Version 5.2.11) date_sub is not working. here is the code: $date = date_create(date('Y-m-d')); date_sub($date, date_interval_create_from_date_string('60 days')); $date1= date_format($date, 'Y-m-d'); but its ok in my localhost(which is in 5.3), but not in server(5.2.11). Can you please tell me how can i make this date subtraction working on 5.2.11 ?

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• An extended Bezier Library or Algorithms of bezier operations

  - by Sorush Rabiee

  Hi, Is there a library of data structures and operations for quadratic bezier curves? I need to implement: bezier to bitmap converting with arbitrary quality optimizing bezier curves common operations like subtraction, extraction, rendering etc. languages: c,c++,.net,python Algorithms without implementation (pseudocode or etc) could be useful too. (especially optimization)

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• video processing with opencv

  - by mithila

  i'm trying to detect car in a video file.i can do background subtraction and the moving cars are visible as foreground object. but i can't draw rectangle around the car. how can i do it? or how can i say in a particular area of the frame there is a car/or there is no car now.please help.

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• Is there a floating point value of x, for which x-x == 0 is false?

  - by Andrew Walker

  In most cases, I understand that a floating point comparison test should be implemented using over a range of values (abs(x-y) < epsilon), but does self subtraction imply that the result will be zero? // can the assertion be triggered? float x = //?; assert( x-x == 0 ) My guess is that nan/inf might be special cases, but I'm more interested in what happens for simple values.

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• What do you call this functional language feature?

  - by Jimmy

  ok, embarrassing enough, I posted code that I need explained. Specifically, it first chains absolute value and subtraction together, then tacks on a sort, all the while not having to mention parameters and arguments at all, because of the presense of "adverbs" that can join these functions "verbs" What (non-APL-type) languages support this kind of no-arguments function composition (I have the vague idea it ties in strongly to the concepts of monad/dyad and rank, but its hard to get a particularly easy-to-understand picture just from reading Wikipedia) and what do I call this concept?

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