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  • Encapsulate standard C functions?

    - by Jack Stout
    While studying the C programming language and learning safe practices, I'm inclined to write a layer of functionality over several parts of the standard library. This would serve two purposes: I could use standard parts of the language in ways that feel more familiar or rational to me, and I could easily replace that functionality with my own, if I needed to. I could benefit from this, but should I do it? As an example, we can consider memory management. If I've written malloc() into the constructors of each of my objects, then decide that I need to handle memory allocation on my own, I have to edit the constructor associated with every object. By referencing my own function, I can change the contents of that function without writing a new constructors. It seems obvious that I should do this, but I'm used to Python. I'm extremely comfortable in that environment and have no problem linking to any part of the standard library from any part of my program because I know I will almost certainly leave that relationship untouched for the life of the project. The situation I'm running into with C feels like I'm trying to hide the language from myself. Will writing a layer of functionality over the C standard library help me in learning the language and developing a codebase, or will it stifle my understanding going forward?

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  • Why are effect-less functions executed?

    - by user828584
    All the languages I know of would execute something like: i = 0 while i < 100000000 i += 1 ..and you can see it take a noticeable amount of time to execute. Why though, do languages do this? The only effect this code will have is taking time. edit: I mean inside a function which is called function main(){ useless() } function useless(){ i = 0 while i < 100000000 i += 1 }

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  • Expected time for lazy evaluation with nested functions?

    - by Matt_JD
    A colleague and I are doing a free R course, although I believe this is a more general lazy evaluation issue, and have found a scenario that we have discussed briefly and I'd like to find out the answer from a wider community. The scenario is as follows (pseudo code): wrapper => function(thing) { print => function() { write(thing) } } v = createThing(1, 2, 3) w = wrapper(v) v = createThing(4, 5, 6) w.print() // Will print 4, 5, 6 thing. v = create(7, 8, 9) w.print() // Will print 4, 5, 6 because "thing" has now been evaluated. Another similar situation is as follows: // Using the same function as above v = createThing(1, 2, 3) v = wrapper(v) w.print() // The wrapper function incestuously includes itself. Now I understand why this happens but where my colleague and I differ is on what should happen. My colleague's view is that this is a bug and the evaluation of the passed in argument should be forced at the point it is passed in so that the returned "w" function is fixed. My view is that I would prefer his option myself, but that I realise that the situation we are encountering is down to lazy evaluation and this is just how it works and is more a quirk than a bug. I am not actually sure of what would be expected, hence the reason I am asking this question. I think that function comments could express what will happen, or leave it to be very lazy, and if the coder using the function wants the argument evaluated then they can force it before passing it in. So, when working with lazy evaulation, what is the practice for the time to evaluate an argument passed, and stored, inside a function?

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  • Using T[1] instead of T for functions overloaded for T(&)[N]

    - by Abyx
    The asio::buffer function has (void*, size_t) and (PodType(&)[N]) overloads. I didn't want to write ugly C-style (&x, sizeof(x)) code, so I wrote this: SomePacket packet[1]; // SomePacket is POD read(socket, asio::buffer(packet)); foo = packet->foo; But that packet-> looks kinda weird - the packet is an array after all. (And packet[0]. doesn't look better.) Now, I think if it was a good idea to write such code. Maybe I should stick to unsafe C-style code with void* and sizeof? Upd: here is another example, for writing a packet: SomePacket packet[1]; // SomePacket is POD packet->id = SomePacket::ID; packet->foo = foo; write(socket, asio::buffer(packet));

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  • Interface design where functions need to be called in a specific sequence

    - by Vorac
    The task is to configure a piece of hardware within the device, according to some input specification. This should be achieved as follows: 1) Collect the configuration information. This can happen at different times and places. For example, module A and module B can both request (at different times) some resources from my module. Those 'resources' are actually what the configuration is. 2) After it is clear that no more requests are going to be realized, a startup command, giving a summary of the requested resources, needs to be sent to the hardware. 3) Only after that, can (and must) detailed configuration of said resources be done. 4) Also, only after 2), can (and must) routing of selected resources to the declared callers be done. A common cause for bugs, even for me, who wrote the thing, is mistaking this order. What naming conventions, designs or mechanisms can I employ to make the interface usable by someone who sees the code for the first time?

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  • How to access functions in extended classes efficiently?

    - by nischayn22
    In PHP I have classes as below class Animal { //some vars public function printname(){ echo $this->name; } } class AnimalMySql extends Animal { static public function getTableFields(){ return array(); } } class AnimalPostgreSql extends Animal { static public function getTableFields(){ return array(); } } Now I have an object $lion = new Animal(); and I want to do if($store == mysql) //getTableFields from class AnimalMySql else //getTableFields form class AnimalPostgreSql I am new to OOP and not sure what is the best way to call the method from the specific class P.S. Please leave a note with the answer to explain the efficiency of the approach

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  • Using the "naked" attribute for functions in GCC

    - by Art Spasky
    GCC documentation (http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html) states in 6.29 Declaring Attributes of Functions "naked Use this attribute on the ARM, AVR, IP2K, RX and SPU ports to indicate that the specified function does not need prologue/epilogue sequences generated by the compiler. It is up to the programmer to provide these sequences. The only statements that can be safely included in naked functions are asm statements that do not have operands. All other statements, including declarations of local variables, if statements, and so forth, should be avoided. Naked functions should be used to implement the body of an assembly function, while allowing the compiler to construct the requisite function declaration for the assembler." Can I safely call functions using C syntax from naked functions, or only by using asm?

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  • 3 hash functions to best hash sliding window strings for a bloom filter with minimum collisions

    - by Duaa
    Hi all: I need 3 hash functions to hash strings of a sliding window moving over a text, to be used later to search within a bloom vector. I'm using C# in my programming I read something about rolling hash functions and cyclic polynomials, they are used for sliding window applications. But really, I did not find any codes, they are just descriptions So please, if anyone have any idea about 3 best C# hash functions to use with sliding window strings of fixed size (5-char), that consume less time and have minimum number of collisions, either they are rolling hash functions or others, please help me with some C# codes or links to hash functions names Duaa

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  • (C++) What's the difference between these overloaded operator functions?

    - by cv3000
    What is the difference between these two ways of overloading the != operator below. Which is consider better? Class Test { ...// private: int iTest public: BOOL operator==(const &Test test) const; BOOL operator!=(const &Test test) const; } BOOL operator==(const &Test test) const { return (iTest == test.iTest); } //overload function 1 BOOL Test::operator!=(const &Test test) const { return !operator==(test); } //overload function 2 BOOL Test::operator!=(const &Test test) const { return (iTest != test.iTest); } I've just recently seen function 1's syntax for calling a sibling operator function and wonder if writing it that way provides any benefits.

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  • Moving Function With Arguments To RequireJS

    - by Jazimov
    I'm not only relatively new to JavaScript but also to RequireJS (coming from string C# background). Currently on my web page I have a number of JavaScript functions. Each one takes two arguments. Imagine that they look like this: functionA(x1, y1) { ... } functionB(x2, y2) { ... } functionC(x3, y3) { ... } Currently, these functions exist in a tag on my HTML page and I simply call each as needed. My functions have dependencies on KnockoutJS, jQuery, and some other JS libraries. I currently have Script tags that synchronously load those external .js dependencies. But I want to use RequireJS so that they're loaded asynchronously, as needed. To do this, I plan to move all three functions above into an external .js file (a type of AMD "module") called MyFunctions.js. That file will have a define() call (to RequireJS's define function) that will look something like this: define(["knockout", "jquery", ...], function("ko","jquery", ...) {???} ); My question is how to "wrap" my functionA, functionB, and functionC functions where the ??? is above so that I can use those functions on my page as needed. For example, in the onclick event handler for a button on my HTML page, I would want to call functionA and pass two it two arguments; same for functionB and functionC. I don't fully understand how to expose those functions when they're wrapped in a define that itself is located in an external .js file. I know that define assures that my listed libraries are loaded asynchronously before the callback function is called, but after that's done I don't understand how the web page's script tags would use my functions. Would I need to use require to ensure they're available, such as: require(["myfunctions"],function({not sure what to put here})] I think I understand the basics of RequireJS but I don't understand how to wrap my functions so that they're in external .js files, don't pollute the global namespace, and yet can still be called from the main page so that arguments can be passed to them. I imagine they're are many ways to do this but in reviewing the RequireJS docs and some videos out there, I can't say I understand how... Thank you for any help.

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  • Generating link-time error for deprecated functions

    - by R..
    Is there a way with gcc and GNU binutils to mark some functions such that they will generate an error at link-time if used? My situation is that I have some library functions which I am not removing for the sake of compatibility with existing binaries, but I want to ensure that no newly-compiled binary tries to make use of the functions. I can't just use compile-time gcc attributes because the offending code is ignoring my headers and detecting the presence of the functions with a configure script and prototyping them itself. My goal is to generate a link-time error for the bad configure scripts so that they stop detecting the existence of the functions.

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  • I just learned about C++ functions; can I use if statements on function return values?

    - by Sagistic
    What I am confused on is about the isNumPalindrome() function. It returns a boolean value of either true or false. How am I suppose to use that so I can display if it's a palindrome or not. For ex. if (isNumPalindrome == true) cout << "Your number is a palindrome"; else cout << "your number is not a palindrome."; #include "stdafx.h" int _tmain(int argc, _TCHAR* argv[]) { return 0; } #include <iostream> #include <cmath> using namespace std; int askNumber(); bool isNumPalindrome(); int num, pwr; int main() { askNumber(); return 0; } bool isNumPalindrome() { int pwr = 0; if (num < 10) return true; else { while (num / static_cast<int>(pow(10.0, pwr)) >=10) pwr++; while (num >=10) { int tenTopwr = static_cast<int>(pow(10.0, pwr)); if ((num / tenTopwr) != (num% 10)) return false; else { num = num % tenTopwr; num = num / 10; pwr = pwr-2; } } return true; } } int askNumber() { cout << "Enter an integer in order to determine if it is a palindrome: " ; cin >> num; cout << endl; if(isNumPalindrome(num)) { cout << "It is a palindrome." ; cout << endl; } else { cout << "It is not a palindrome." ; cout << endl; } return num; }

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  • How do I print values of an array in Three Rows?

    - by Ramkumar
    I need this output.. 1 3 5 2 4 6 I want to use array function like array(1,2,3,4,5,6). If I edit this array like array(1,2,3), it means the output need to show like 1 2 3 The concept is maximum 3 column only. If we give array(1,2,3,4,5), it means the output should be 1 3 5 2 4 Suppose we will give array(1,2,3,4,5,6,7,8,9), then it means output is 1 4 7 2 5 8 3 6 9 that is, maximum 3 column only. Depends upon the the given input, the rows will be created with 3 columns. Is this possible with PHP? I am doing small Research & Development in array functions. I think this is possible. Will you help me? For more info: * input: array(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15) * output: 1 6 11 2 7 12 3 8 13 4 9 14 5 10 15

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  • Best Method of function parameter validation

    - by Aglystas
    I've been dabbling with the idea of creating my own CMS for the experience and because it would be fun to run my website off my own code base. One of the decisions I keep coming back to is how best to validate incoming parameters for functions. This is mostly in reference to simple data types since object validation would be quite a bit more complex. At first I debated creating a naming convention that would contain information about what the parameters should be, (int, string, bool, etc) then I also figured I could create options to validate against. But then in every function I still need to run some sort of parameter validation that parses the parameter name to determine what the value can be then validate against it, granted this would be handled by passing the list of parameters to function but that still needs to happen and one of my goals is to remove the parameter validation from the function itself so that you can only have the actual function code that accomplishes the intended task without the additional code for validation. Is there any good way of handling this, or is it so low level that typically parameter validation is just done at the start of the function call anyway, so I should stick with doing that.

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  • Notepad++: Adding color highlighting for PHP functions?

    - by Jebego
    I've recently begun using Notepad++, and have found a part of its styling functionality that confuses me. I'm currently attempting to color all of PHP's defined functions (such as count(), strlen(), etc.). In the Settings-Style Configurator, you cannot add a new style for such a function list. Instead, I have begun editing the stylers.xml and langs.xml. To add the new coloring, in langs.xml, I've modified the php section to the following: <Language name="php" ext="php php3 phtml" commentLine="//" commentStart="/*" commentEnd="*/"> <Keywords name="instre1">[default keywords]</Keywords> <Keywords name="instre2">[my function list]</Keywords> </Language> The [default keywords] and [my function list] are replaced with wordlists. I've also edited the php section in stylers.xml to look like the following: <LexerType name="php" desc="php" ext=""> <WordsStyle name="QUESTION MARK" styleID="18" fgColor="FF0000" bgColor="FDF8E3" fontName="" fontStyle="0" fontSize="" /> <WordsStyle name="DEFAULT" styleID="118" fgColor="000000" bgColor="FEFCF5" fontName="" fontStyle="0" fontSize="" /> <WordsStyle name="STRING" styleID="119" fgColor="FF0000" bgColor="FEFCF5" fontName="" fontStyle="0" fontSize="" /> <WordsStyle name="STRING VARIABLE" styleID="126" fgColor="FF0000" bgColor="FEFCF5" fontName="" fontStyle="1" fontSize="" /> <WordsStyle name="SIMPLESTRING" styleID="120" fgColor="FF0000" bgColor="FEFCF5" fontName="" fontStyle="0" fontSize="" /> <WordsStyle name="WORD" styleID="121" fgColor="008040" bgColor="FEFCF5" fontName="" fontStyle="1" fontSize="" keywordClass="instre1">True False</WordsStyle> <WordsStyle name="NUMBER" styleID="122" fgColor="FF0000" bgColor="FEFCF5" fontName="" fontStyle="0" fontSize="" /> <WordsStyle name="VARIABLE" styleID="123" fgColor="0080FF" bgColor="FEFCF5" fontName="" fontStyle="0" fontSize="" /> <WordsStyle name="COMMENT" styleID="124" fgColor="FF8040" bgColor="FEFCF5" fontName="" fontStyle="0" fontSize="" /> <WordsStyle name="COMMENTLINE" styleID="125" fgColor="FF8040" bgColor="FEFCF5" fontName="" fontStyle="0" fontSize="" /> <WordsStyle name="OPERATOR" styleID="127" fgColor="8000FF" bgColor="FEFCF5" fontName="" fontStyle="0" fontSize="" /> <WordsStyle name="FUNCTIONS" styleID="128" fgColor="000080" bgColor="FEFCF5" fontName="" fontStyle="1" fontSize="" keywordClass="instre2"></WordsStyle> </LexerType> The changed part is the last "FUNCTIONS" line. When I restart Notepad++ and go into the Settings-Style Configurator section, under the php language, the FUNCTIONS style exists. I can change the style's color, and can see the entire keyword list under 'Default Keywords'. However, it is not changing the coloring of the words in my code. When I edit the WORD style, which contains stuff like 'if', 'and', and 'true', things change accordingly in my code. Any ideas on how to make this work?

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  • Replicating common Excel Functions

    - by datatoo
    I am always curious how some of the functions I use in excel were written, and think it would help at times to see how it was done. Does anyone know where there is example vba that replicates what some of these functions do? vlookup, hlookup, dsum, index, actually any or most would be interesting.

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  • Why does Scala require functions to have explicit return type?

    - by garbage collection
    I recently began learning to program in Scala, and it's been fun so far. I really like the ability to declare functions within another function which just seems to intuitive thing to do. One pet peeve I have about Scala is the fact that Scala requires explicit return type in its functions. And I feel like this hinders on expressiveness of the language. Also it's just difficult to program with that requirement. Maybe it's because I come from Javascript and Ruby comfort zone. But for a language like Scala which will have tons of connected functions in an application, I cannot conceive how I brainstorm in my head exactly what type the particular function I am writing should return with recursions after recursions. This requirement of explicit return type declaration on functions, do not bother me for languages like Java and C++. Recursions in Java and C++, when they did happen, often were dealt with 2 to 3 functions max. Never several functions chained up together like Scala. So I guess I'm wondering if there is a good reason why Scala should have the requirement of functions having explicit return type?

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  • What Precalculus knowledge is required before learning Discrete Math Computer Science topics?

    - by Ein Doofus
    Below I've listed the chapters from a Precalculus book as well as the author recommended Computer Science chapters from a Discrete Mathematics book. Although these chapters are from two specific books on these subjects I believe the topics are generally the same between any Precalc or Discrete Math book. What Precalculus topics should one know before starting these Discrete Math Computer Science topics?: Discrete Mathematics CS Chapters 1.1 Propositional Logic 1.2 Propositional Equivalences 1.3 Predicates and Quantifiers 1.4 Nested Quantifiers 1.5 Rules of Inference 1.6 Introduction to Proofs 1.7 Proof Methods and Strategy 2.1 Sets 2.2 Set Operations 2.3 Functions 2.4 Sequences and Summations 3.1 Algorithms 3.2 The Growths of Functions 3.3 Complexity of Algorithms 3.4 The Integers and Division 3.5 Primes and Greatest Common Divisors 3.6 Integers and Algorithms 3.8 Matrices 4.1 Mathematical Induction 4.2 Strong Induction and Well-Ordering 4.3 Recursive Definitions and Structural Induction 4.4 Recursive Algorithms 4.5 Program Correctness 5.1 The Basics of Counting 5.2 The Pigeonhole Principle 5.3 Permutations and Combinations 5.6 Generating Permutations and Combinations 6.1 An Introduction to Discrete Probability 6.4 Expected Value and Variance 7.1 Recurrence Relations 7.3 Divide-and-Conquer Algorithms and Recurrence Relations 7.5 Inclusion-Exclusion 8.1 Relations and Their Properties 8.2 n-ary Relations and Their Applications 8.3 Representing Relations 8.5 Equivalence Relations 9.1 Graphs and Graph Models 9.2 Graph Terminology and Special Types of Graphs 9.3 Representing Graphs and Graph Isomorphism 9.4 Connectivity 9.5 Euler and Hamilton Ptahs 10.1 Introduction to Trees 10.2 Application of Trees 10.3 Tree Traversal 11.1 Boolean Functions 11.2 Representing Boolean Functions 11.3 Logic Gates 11.4 Minimization of Circuits 12.1 Language and Grammars 12.2 Finite-State Machines with Output 12.3 Finite-State Machines with No Output 12.4 Language Recognition 12.5 Turing Machines Precalculus Chapters R.1 The Real-Number System R.2 Integer Exponents, Scientific Notation, and Order of Operations R.3 Addition, Subtraction, and Multiplication of Polynomials R.4 Factoring R.5 Rational Expressions R.6 Radical Notation and Rational Exponents R.7 The Basics of Equation Solving 1.1 Functions, Graphs, Graphers 1.2 Linear Functions, Slope, and Applications 1.3 Modeling: Data Analysis, Curve Fitting, and Linear Regression 1.4 More on Functions 1.5 Symmetry and Transformations 1.6 Variation and Applications 1.7 Distance, Midpoints, and Circles 2.1 Zeros of Linear Functions and Models 2.2 The Complex Numbers 2.3 Zeros of Quadratic Functions and Models 2.4 Analyzing Graphs of Quadratic Functions 2.5 Modeling: Data Analysis, Curve Fitting, and Quadratic Regression 2.6 Zeros and More Equation Solving 2.7 Solving Inequalities 3.1 Polynomial Functions and Modeling 3.2 Polynomial Division; The Remainder and Factor Theorems 3.3 Theorems about Zeros of Polynomial Functions 3.4 Rational Functions 3.5 Polynomial and Rational Inequalities 4.1 Composite and Inverse Functions 4.2 Exponential Functions and Graphs 4.3 Logarithmic Functions and Graphs 4.4 Properties of Logarithmic Functions 4.5 Solving Exponential and Logarithmic Equations 4.6 Applications and Models: Growth and Decay 5.1 Systems of Equations in Two Variables 5.2 System of Equations in Three Variables 5.3 Matrices and Systems of Equations 5.4 Matrix Operations 5.5 Inverses of Matrices 5.6 System of Inequalities and Linear Programming 5.7 Partial Fractions 6.1 The Parabola 6.2 The Circle and Ellipse 6.3 The Hyperbola 6.4 Nonlinear Systems of Equations

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  • Database Version Control SQL Server 2008 Drop SP's and Functions

    - by Lieven Cardoen
    I'm working on versioning our database and now searching for a way to drop all stored procedures and functions from a C# Console Application. I'd rather not create a stored procedure that drops all stored procedures and functions. I has to be some sql executed from C#. I tried to drop the stored procedure before creating it, but I get this message: System.Data.SqlClient.SqlException: 'CREATE/ALTER PROCEDURE' must be the first statement in a query batch. Script for one SP for example: DROP PROCEDURE [dbo].[sp_Economatic_LoadJournalEntryFeedbackByData] SET ANSI_NULLS ON SET QUOTED_IDENTIFIER ON CREATE PROCEDURE [dbo].[sp_Economatic_LoadJournalEntryFeedbackByData] @Data VARCHAR(MAX) AS BEGIN ... END So I guess before creating all SP's and functions I'll need to drop all SP's and functions first with one sql script.

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