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  • C++ putting a 2d array of floats into a char*

    - by sam
    Hello, I'm trying to take a 2d vector of floats (input) and put them into a char* (output) in c++. void foo(const std::vector<std::vector<float> > &input, char* &output ) { char charBuf[sizeof(output)]; int counter = 0; for(unsigned int i=0; i<input.size(); i++) { for(unsigned int p=0; p<input.at(i).size(); p++) { //what the heck goes here } }

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  • Why subtract a value from itself (x - x) in Python?

    - by endolith
    In NumPy functions, there are often initial lines that do checking of variable types, forcing them to be certain types, etc. Can someone explain the point of these lines? What does subtracting a value from itself do? t,w = asarray(t), asarray(duty) w = asarray(w + (t-t)) t = asarray(t + (w-w))

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  • Cannot convert []string to []interface {}

    - by karlrh
    I'm writing some code, and I need it to catch the arguments and pass them through fmt.Println (I want its default behaviour, to write arguments separated by spaces and followed by a newline). However it takes []interface {} but flag.Args() returns a []string. Here's the code example package main import ( "fmt" "flag" ) func main() { flag.Parse() fmt.Println(flag.Args()...) } This returns the following error: ./example.go:10: cannot use args (type []string) as type []interface {} in function argument Is this a bug? Shouldn't fmt.Println take any array? By the way, I've also tried to do this: var args = []interface{}(flag.Args()) but I get the following error: cannot convert flag.Args() (type []string) to type []interface {} Is there a "Go" way to workaround this?

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  • Conversion of pointer-to-pointer between derived and base classes?

    - by Mike Mueller
    Regarding the following C++ program: class Base { }; class Child : public Base { }; int main() { // Normal: using child as base is allowed Child *c = new Child(); Base *b = c; // Double pointers: apparently can't use Child** as Base** Child **cc = &c; Base **bb = cc; return 0; } GCC produces the following error on the last assignment statement: error: invalid conversion from ‘Child**’ to ‘Base**’ My question is in two parts: Why is there no implicit conversion from Child** to Base**? I can make this example work with a C-style cast or a reinterpret_cast. Using these casts means throwing away all type safety. Is there anything I can add to the class definitions to make these pointers cast implicitly, or at least phrase the conversion in a way that allows me to use static_cast instead?

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  • Prolog Beginner: How to unify with arithmentic comparison operators or how to get a set var to range

    - by sixtyfootersdude
    I am new to prolog. I need to write an integer adder that will add numbers between 0-9 to other numbers 0-9 and produce a solution 0-18. This is what I want to do: % sudo code add(in1, in2, out) :- in1 < 10, in2 < 10, out < 18. I would like to be able to call it like this: To Check if it is a valid addition: ?- add(1,2,3). true ?- add(1,2,4). false With one missing variable: ?- add(X,2,3). 1 ?- add(1,4,X). 5 With multiple missing variables: ?-add(X,Y,Z). % Some output that would make sense. Some examples could be: X=1, Y=1, Z=2 ; X=2, Y=1, Z=3 ...... I realize that this is probably a pretty simplistic question and it is probably very straightforward. However cording to the prolog tutorial I am using: "Unlike unification Arithmetic Comparison Operators operators cannot be used to give values to a variable. The can only be evaluated when every term on each side have been instantiated."

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  • Are ternary operators not valid for linq-to-sql queries?

    - by KallDrexx
    I am trying to display a nullable date time in my JSON response. In my MVC Controller I am running the following query: var requests = (from r in _context.TestRequests where r.scheduled_time == null && r.TestRequestRuns.Count > 0 select new { id = r.id, name = r.name, start = DateAndTimeDisplayString(r.TestRequestRuns.First().start_dt), end = r.TestRequestRuns.First().end_dt.HasValue ? DateAndTimeDisplayString(r.TestRequestRuns.First().end_dt.Value) : string.Empty }); When I run requests.ToArray() I get the following exception: Could not translate expression ' Table(TestRequest) .Where(r => ((r.scheduled_time == null) AndAlso (r.TestRequestRuns.Count > 0))) .Select(r => new <>f__AnonymousType18`4(id = r.id, name = r.name, start = value(QAWebTools.Controllers.TestRequestsController). DateAndTimeDisplayString(r.TestRequestRuns.First().start_dt), end = IIF(r.TestRequestRuns.First().end_dt.HasValue, value(QAWebTools.Controllers.TestRequestsController). DateAndTimeDisplayString(r.TestRequestRuns.First().end_dt.Value), Invoke(value(System.Func`1[System.String])))))' into SQL and could not treat it as a local expression. If I comment out the end = line, everything seems to run correctly, so it doesn't seem to be the use of my local DateAndTimeDisplayString method, so the only thing I can think of is Linq to Sql doesn't like Ternary operators? I think I've used ternary operators before, but I can't remember if I did it in this code base or another code base (that uses EF4 instead of L2S). Is this true, or am I missing some other issue?

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  • Checked and Unchecked operators don't seem to be working when...

    - by flockofcode
    1) Is UNCHECKED operator in effect only when expression inside UNCHECKED context uses an explicit cast ( such as byte b1=unchecked((byte)2000); ) and when conversion to particular type can happen implicitly? I’m assuming this since the following expression throws a compile time error: byte b1=unchecked(2000); //compile time error 2) a) Do CHECKED and UNCHECKED operators work only when resulting value of an expression or conversion is of an integer type? I’m assuming this since in the first example ( where double type is being converted to integer type ) CHECKED operator works as expected: double m = double.MaxValue; b=checked((byte)m); // reports an exception , while in second example ( where double type is being converted to a float type ) CHECKED operator doesn’t seem to be working. since it doesn't throw an exception: double m = double.MaxValue; float f = checked((float)m); // no exception thrown b) Why don’t the two operators also work with expressions where type of a resulting value is of floating-point type? 2) Next quote is from Microsoft’s site: The unchecked keyword is used to control the overflow-checking context for integral-type arithmetic operations and conversions I’m not sure I understand what exactly have expressions and conversions such as unchecked((byte)(100+200)); in common with integrals? Thank you

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  • Prolog Beginner: How to unify with arithmentic cmparison operators or how to get a set var to range

    - by sixtyfootersdude
    I am new to prolog. I need to write an integer adder that will add numbers between 0-9 to other numbers 0-9 and produce a solution 0-18. This is what I want to do: add(in1, in2, out) :- in1 < 10, in2 < 10, out < 18. I would like to be able to call it like this: To Check if it is a valid addition: ?- add(1,2,3). true ?- add(1,2,4). false With one missing variable: ?- add(X,2,3). 1 ?- add(1,4,X). 5 With multiple missing variables: ?-add(X,Y,Z). % Some output that would make sense. Some examples could be: X=1, Y=1, Z=2 ; X=2, Y=1, Z=3 ...... I realize that this is probably a pretty simplistic question and it is probably very straightforward. However cording to the prolog tutorial I am using: "Unlike unification Arithmetic Comparison Operators operators cannot be used to give values to a variable. The can only be evaluated when every term on each side have been instantiated."

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  • What does the C# compiler mean when it prints "an explicit conversion exists"?

    - by Wim Coenen
    If I make an empty test class: public class Foo { } And I try to compile code with this statement: Foo foo = "test"; Then I get this error as expected: Cannot implicitly convert type 'string' to 'ConsoleApplication1.Foo' However, if I change the declaration of Foo from class to interface, the error changes to this (emphasis mine): Cannot implicitly convert type 'string' to 'ConsoleApplication1.Foo'. An explicit conversion exists (are you missing a cast?) What is this "explicit conversion" which is supposed to exist?

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  • How do I go about overloading C++ operators to allow for chaining?

    - by fneep
    I, like so many programmers before me, am tearing my hair out writing the right-of-passage-matrix-class-in-C++. I have never done very serious operator overloading and this is causing issues. Essentially, by stepping through This is what I call to cause the problems. cMatrix Kev = CT::cMatrix::GetUnitMatrix(4, true); Kev *= 4.0f; cMatrix Baz = Kev; Kev = Kev+Baz; //HERE! What seems to be happening according to the debugger is that Kev and Baz are added but then the value is lost and when it comes to reassigning to Kev, the memory is just its default dodgy values. How do I overload my operators to allow for this statement? My (stripped down) code is below. //header class cMatrix { private: float* _internal; UInt32 _r; UInt32 _c; bool _zeroindexed; //fast, assumes zero index, no safety checks float cMatrix::_getelement(UInt32 r, UInt32 c) { return _internal[(r*this->_c)+c]; } void cMatrix::_setelement(UInt32 r, UInt32 c, float Value) { _internal[(r*this->_c)+c] = Value; } public: cMatrix(UInt32 r, UInt32 c, bool IsZeroIndexed); cMatrix( cMatrix& m); ~cMatrix(void); //operators cMatrix& operator + (cMatrix m); cMatrix& operator += (cMatrix m); cMatrix& operator = (const cMatrix &m); }; //stripped source file cMatrix::cMatrix(cMatrix& m) { _r = m._r; _c = m._c; _zeroindexed = m._zeroindexed; _internal = new float[_r*_c]; UInt32 size = GetElementCount(); for (UInt32 i = 0; i < size; i++) { _internal[i] = m._internal[i]; } } cMatrix::~cMatrix(void) { delete[] _internal; } cMatrix& cMatrix::operator+(cMatrix m) { return cMatrix(*this) += m; } cMatrix& cMatrix::operator*(float f) { return cMatrix(*this) *= f; } cMatrix& cMatrix::operator*=(float f) { UInt32 size = GetElementCount(); for (UInt32 i = 0; i < size; i++) { _internal[i] *= f; } return *this; } cMatrix& cMatrix::operator+=(cMatrix m) { if (_c != m._c || _r != m._r) { throw new cCTException("Cannot add two matrix classes of different sizes."); } if (!(_zeroindexed && m._zeroindexed)) { throw new cCTException("Zero-Indexed mismatch."); } for (UInt32 row = 0; row < _r; row++) { for (UInt32 column = 0; column < _c; column++) { float Current = _getelement(row, column) + m._getelement(row, column); _setelement(row, column, Current); } } return *this; } cMatrix& cMatrix::operator=(const cMatrix &m) { if (this != &m) { _r = m._r; _c = m._c; _zeroindexed = m._zeroindexed; delete[] _internal; _internal = new float[_r*_c]; UInt32 size = GetElementCount(); for (UInt32 i = 0; i < size; i++) { _internal[i] = m._internal[i]; } } return *this; }

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  • How can I modify my Shunting-Yard Algorithm so it accepts unary operators?

    - by KingNestor
    I've been working on implementing the Shunting-Yard Algorithm in JavaScript for class. Here is my work so far: var userInput = prompt("Enter in a mathematical expression:"); var postFix = InfixToPostfix(userInput); var result = EvaluateExpression(postFix); document.write("Infix: " + userInput + "<br/>"); document.write("Postfix (RPN): " + postFix + "<br/>"); document.write("Result: " + result + "<br/>"); function EvaluateExpression(expression) { var tokens = expression.split(/([0-9]+|[*+-\/()])/); var evalStack = []; while (tokens.length != 0) { var currentToken = tokens.shift(); if (isNumber(currentToken)) { evalStack.push(currentToken); } else if (isOperator(currentToken)) { var operand1 = evalStack.pop(); var operand2 = evalStack.pop(); var result = PerformOperation(parseInt(operand1), parseInt(operand2), currentToken); evalStack.push(result); } } return evalStack.pop(); } function PerformOperation(operand1, operand2, operator) { switch(operator) { case '+': return operand1 + operand2; case '-': return operand1 - operand2; case '*': return operand1 * operand2; case '/': return operand1 / operand2; default: return; } } function InfixToPostfix(expression) { var tokens = expression.split(/([0-9]+|[*+-\/()])/); var outputQueue = []; var operatorStack = []; while (tokens.length != 0) { var currentToken = tokens.shift(); if (isNumber(currentToken)) { outputQueue.push(currentToken); } else if (isOperator(currentToken)) { while ((getAssociativity(currentToken) == 'left' && getPrecedence(currentToken) <= getPrecedence(operatorStack[operatorStack.length-1])) || (getAssociativity(currentToken) == 'right' && getPrecedence(currentToken) < getPrecedence(operatorStack[operatorStack.length-1]))) { outputQueue.push(operatorStack.pop()) } operatorStack.push(currentToken); } else if (currentToken == '(') { operatorStack.push(currentToken); } else if (currentToken == ')') { while (operatorStack[operatorStack.length-1] != '(') { if (operatorStack.length == 0) throw("Parenthesis balancing error! Shame on you!"); outputQueue.push(operatorStack.pop()); } operatorStack.pop(); } } while (operatorStack.length != 0) { if (!operatorStack[operatorStack.length-1].match(/([()])/)) outputQueue.push(operatorStack.pop()); else throw("Parenthesis balancing error! Shame on you!"); } return outputQueue.join(" "); } function isOperator(token) { if (!token.match(/([*+-\/])/)) return false; else return true; } function isNumber(token) { if (!token.match(/([0-9]+)/)) return false; else return true; } function getPrecedence(token) { switch (token) { case '^': return 9; case '*': case '/': case '%': return 8; case '+': case '-': return 6; default: return -1; } } function getAssociativity(token) { switch(token) { case '+': case '-': case '*': case '/': return 'left'; case '^': return 'right'; } } It works fine so far. If I give it: ((5+3) * 8) It will output: Infix: ((5+3) * 8) Postfix (RPN): 5 3 + 8 * Result: 64 However, I'm struggling with implementing the unary operators so I could do something like: ((-5+3) * 8) What would be the best way to implement unary operators (negation, etc)? Also, does anyone have any suggestions for handling floating point numbers as well? One last thing, if anyone sees me doing anything weird in JavaScript let me know. This is my first JavaScript program and I'm not used to it yet.

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  • Ever any performance different between Java >> and >>> right shift operators?

    - by Sean Owen
    Is there ever reason to think the (signed) and (unsigned) right bit-shift operators in Java would perform differently? I can't detect any difference on my machine. This is purely an academic question; it's never going to be the bottleneck I'm sure. I know: it's best to write what you mean foremost; use for division by 2, for example. I assume it comes down to which architectures have which operations implemented as an instruction.

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  • How do languages handle side effects of compound operators?

    - by Kos
    Hello, Assume such situation: int a = (--t)*(t-2); int b = (t/=a)+t; In C and C++ this is undefined behaviour, as described here: Undefined Behavior and Sequence Points However, how does this situation look in: JavaScript, Java, PHP... C# well, any other language which has compound operators? I'm bugfixing a Javascript - C++ port right now in which this got unnoticed in many places. I'd like to know how other languages generally handle this... Leaving the order undefined is somehow specific to C and C++, isn't it?

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  • Can I customize the indentation of ternary operators in emacs' cperl-mode?

    - by Ryan Thompson
    In emacs cperl-mode, ternary operators are not treated specially. If you break them over multiple lines, cperl-mode simply indents each line the same way it indents any continued statement, like this: $result = ($foo == $bar) ? 'result1' : ($foo == $baz) ? 'result2' : ($foo == $qux) ? 'result3' : ($foo == $quux) ? 'result4' : fail_result; This is not very readable. Is there some way that I can convince cperl-mode indent like this? $result = ($foo == $bar) ? 'result1' : ($foo == $baz) ? 'result2' : ($foo == $qux) ? 'result3' : ($foo == $quux) ? 'result4' : fail_result; By the way, code example from this question.

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  • C/C++: Who uses the logical operator macros from iso646.h and why?

    - by Jaime Soto
    There has been some debate at work about using the merits of using the alternative spellings for C/C++ logical operators in iso646.h: and && and_eq &= bitand & bitor | compl ~ not ! not_eq != or || or_eq |= xor ^ xor_eq ^= According to Wikipedia, these macros facilitate typing logical operators in international (non-US English?) and non-QWERTY keyboards. All of our development team is in the same office in Orlando, FL, USA and from what I have seen we all use the US English QWERTY keyboard layout; even Dvorak provides all the necessary characters. Supporters of using the iso646.h macros claim we should them because they are part of the C and C++ standards. I think this argument is moot since digraphs and trigraphs are also part of these standards and they are not even supported by default in many compilers. My rationale for opposing these macros in our team is that we do not need them since: Everybody on our team uses the US English QWERTY keyboard layout; C and C++ programming books from the US barely mention iso646.h, if at all; and new developers may not be familiar with iso646.h (this is expected if they are from the US). /rant Finally, to my set of questions: Does anyone in this site use the iso646.h logical operator macros? Why? What is your opinion about using the iso646.h logical operator macros in code written and maintained on US English QWERTY keyboards? Is my digraph and trigraph analogy a valid argument against using iso646.h with US English QWERTY keyboard layouts? EDIT: I missed two similar questions in StackOverflow: Is anybody using the named boolean operators? Which C++ logical operators do you use: and, or, not and the ilk or C style operators? why?

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  • Do AdWords conversions only track AdWords visitors?

    - by atticae
    I have set up an AdWords conversion and put the conversion tracking JS code on a test page. However, I don't see any conversions tracked when I visit it. Does the AdWords conversion tracking only register your conversion if you come to the site by clicking on an AdWords campaign? Google's help page advises me to test the code by clicking a campaign. However, I would like to use the tracking to track all conversions, not just AdWords. I considered using Analytics as well, but it seems you can only track via url there, not JS, which would mean I had to restructure a part of my page. (Because currently a conversion appears does not necessarily happen on a different URL.) Is AdWords tracking not a viable solution to track all visitor conversions on my site?

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  • How to measure the conversion rate of your Amazon affiliate program?

    - by user359650
    I plan on selling products through the Amazon affiliate program. What I know I can track is: -what products people view on my website (default Google Analytics pageview behaviour). -what affiliate links people click on my website (with GA _trackEvent). What am I missing is: -what products people end up buying after clicking on the affiliate links. Does the Amazon affiliate program offers you any mechanism for linking a purchase with some data from your website? I noticed that I was able to add custom parameters and values to my affiliate links and the link checker was still happy with them, if Amazon gave the links that initiated an order then I would be able to cross reference the orders using custom parameters...

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  • how do I register a custom conversion Service in spring 3 / webflow 2?

    - by nont
    I've been trying to follow this example and using the reference to guide me, but I'm having no luck. I've defined a converter: import org.springframework.binding.convert.converters.StringToObject; import java.text.DateFormat; import java.text.SimpleDateFormat; import java.text.ParseException; import java.util.Date; public class StringToDateTwoWayConverter extends StringToObject { private DateFormat format = null; public StringToDateTwoWayConverter () { super(StringToDateTwoWayConverter.class); format = new SimpleDateFormat("MM/dd/yyyy"); } @Override protected Object toObject(String string, Class targetClass) throws Exception { Date date = null; try { date = format.parse(string); } catch (ParseException e) { e.printStackTrace(); return null; } return date; } @Override protected String toString(Object object) throws Exception { Date date = (Date) object; return format.format(date); } } and a conversionService: import org.springframework.binding.convert.service.DefaultConversionService; import org.springframework.stereotype.Component; @Component("conversionService") public class ApplicationConversionService extends DefaultConversionService { @Override protected void addDefaultConverters() { super.addDefaultConverters(); this.addConverter(new StringToDateTwoWayConverter()); this.addConverter("shortDate", new StringToDateTwoWayConverter()); } } and configured it: <webflow:flow-builder-services id="flowBuilderServices" conversion-service="conversionService" .../> However, upon startup, I'm greeted with this exception: Caused by: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name '(inner bean)': Unsatisfied dependency expressed through constructor argument with index 0 of type [org.springframework.core.convert.ConversionService]: Could not convert constructor argument value of type [com.yadayada.converter.ApplicationConversionService] to required type [org.springframework.core.convert.ConversionService]: Failed to convert value of type 'com.yadayada.converter.ApplicationConversionService' to required type 'org.springframework.core.convert.ConversionService'; nested exception is java.lang.IllegalStateException: Cannot convert value of type [com.yadayada.converter.ApplicationConversionService] to required type [org.springframework.core.convert.ConversionService]: no matching editors or conversion strategy found at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:687) at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:195) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:993) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:897) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:485) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456) at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveInnerBean(BeanDefinitionValueResolver.java:270) ... 60 more I'm thoroughly puzzled why its not working. The conversion service implements ConversionService through its base class, so I don't see the problem. Any insight much appreciated!

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  • Generic structure for performing string conversion when data binding.

    - by Rohan West
    Hi there, a little while ago i was reading an article about a series of class that were created that handled the conversion of strings into a generic type. Below is a mock class structure. Basically if you set the StringValue it will perform some conversion into type T public class MyClass<T> { public string StringValue {get;set;} public T Value {get;set;} } I cannot remember the article that i was reading, or the name of the class i was reading about. Is this already implemented in the framework? Or shall i create my own?

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