comparison-operators

I need to run several queries against columns containing both positive and negative numbers and return all rows that are either < or > than a selected value, however it's not returning the expected results when I use a 'Greater than' operator if the selected value is a negative number. Please note that when the selected value is a negative number it should be returning both positive and negative numbers, and it seems to be excluding the negative numbers from the results. SELECT T3.* FROM Rules T3 WHERE T3.Width > '-.80'; The values contained in T3.Width are: 0.90,(0.70),(0.70),(0.70),(0.70),(1

I had always thought that the standard required the non-specialized template for std::equal_to<T> to call T::operator== , but I noticed the description at cppreference.com almost implies it's the other way around; certainly it doesn't mention it as a requirement. I also checked the C++11 draft standard N3337 and couldn't find any guarantees there either. If you create a class with an operator== you'd hope it would get used in all circumstances. I can't honestly think of a way to implement std::equal_to that wouldn't work this way, but am I missing something? Is std::equal_to guaranteed to call

I would like to expose C++ code with a std::vector<A> to python. My class A{}; does not have a comparison operator implemented. When I try BOOST_PYTHON_MODULE(libmyvec) { using namespace boost::python; class_<A>("A"); class_<std::vector<A> >("Avec") .def(boost::python::vector_indexing_suite<std::vector<A> >()); } I get an error about comparison operators. If I change the definition of A to class A { public: bool operator==(const A& other) {return false;} bool operator!=(const A& other) {return true;} }; It works like a charm. Why do I need to implement these comparison operators? Is there any

This question already has answers here : Why does >= return false when == returns true for null values? (8 answers) Closed 2 years ago . Why is it that in .NET null >= null resolves as false, but null == null resolves as true? In other words, why isn't null >= null equivalent to null > null || null == null ? Does anyone have the official answer? This behaviour is defined in the C# specification ( ECMA-334 ) in section 14.2.7 (I have highlighted the relevant part): For the relational operators < > <= >= a lifted form of an operator exists if the operand types are both non-nullable value types

I'm working on a simple linked list implementation in golang for learning purposes. The definition of an element is below: type Element struct { next, prev *Element Value interface{} } As you can see, the Value can be anything that satisfies the empty interface. Now, as a new feature, I would like to make it so that when you insert a new element into the list, it inserts it in a sorted manner - each element will be <= the next. In order to do this, I wrote the following method: func (l *LinkedList) Add(val interface{}) *Element { this := &l.Root e := Element{Value: val} for { if this.next

I would like to make a function with a parameter that accepts either std::greater<int> or std::less<int> as the argument. I'm stuck on the syntax for the parameter, though. This is the format I tried: myFunction(int a, int b, bool *comp(int, int)) { … } … std::greater<int> bigger; myFunction(2, 3, bigger); That doesn't work, though, and I suspect the third parameter is just completely wrong. What should it actually be? cannot convert std::greater<int> to bool* (*)(int, int) user1942027 Functions taking a comparator are usually implemented via templates: template <typename Comparator>

Under C++ or <stdbool.h> from C99, how is the less-than operator < defined for boolean values? Alternatively, explain the behaviour of this code: #ifndef __cplusplus #include <stdbool.h> #endif #include <stdio.h> int main() { bool b = -1; if(b < true) { printf("b < true\n"); } if(b < false) { printf("b < false\n"); } if(true < false) { printf("true < false\n"); } if(false < true) { printf("false < true\n"); } } Under MSVC version 10, compiled as C++ code, GCC 4.6.3-ubuntu5 compiled as C code and G++ 4.6.3-1ubuntu5 compiled as C++ code, all you get is false < true That is, the following