numeric-limits

问题 When I run this code: #include <limits> #include <cstdio> #define T double int main() { static const T val = std::numeric_limits<T>::min(); printf( "%g/2 = %g\n", val, val/2 ); } I would expect to see an unpredictable result. But I get the correct answer: (16:53) > clang++ test_division.cpp -o test_division (16:54) > ./test_division 2.22507e-308/2 = 1.11254e-308 How is this possible? 回答1: Because min gives you the smallest normalized value. You can still have smaller denormalized values (see

问题 When I run this code: #include <limits> #include <cstdio> #define T double int main() { static const T val = std::numeric_limits<T>::min(); printf( "%g/2 = %g\n", val, val/2 ); } I would expect to see an unpredictable result. But I get the correct answer: (16:53) > clang++ test_division.cpp -o test_division (16:54) > ./test_division 2.22507e-308/2 = 1.11254e-308 How is this possible? 回答1: Because min gives you the smallest normalized value. You can still have smaller denormalized values (see

问题 When I run this code: #include <limits> #include <cstdio> #define T double int main() { static const T val = std::numeric_limits<T>::min(); printf( "%g/2 = %g\n", val, val/2 ); } I would expect to see an unpredictable result. But I get the correct answer: (16:53) > clang++ test_division.cpp -o test_division (16:54) > ./test_division 2.22507e-308/2 = 1.11254e-308 How is this possible? 回答1: Because min gives you the smallest normalized value. You can still have smaller denormalized values (see

问题 I'm trying to obtain the maximum value of a certain unsigned integer type without including any headers like <limits> . So I thought I'd simply flip the bits of the unsigned integer value 0. #include <iostream> #include <limits> int main() { std::cout << (~0U) << '\n'; // #1 std::cout << (std::numeric_limits< unsigned >::max()) << '\n'; // #2 return 0; } I'm not very experienced on the subtle differences between these. Which is why I'm asking if some unexpected behavior or some platform

问题 I'm trying to obtain the maximum value of a certain unsigned integer type without including any headers like <limits> . So I thought I'd simply flip the bits of the unsigned integer value 0. #include <iostream> #include <limits> int main() { std::cout << (~0U) << '\n'; // #1 std::cout << (std::numeric_limits< unsigned >::max()) << '\n'; // #2 return 0; } I'm not very experienced on the subtle differences between these. Which is why I'm asking if some unexpected behavior or some platform

问题 I want to know if there is something in the standard, like a #define or something in numeric_limits which would tell me the maximum number of base-10 digits in the integral part of a floating point type. For example, if I have some floating point type the largest value of which is: 1234.567. I'd like something defined in the standard that would tell me 4 for that type. Is there an option to me doing this? template <typename T> constexpr auto integral_digits10 = static_cast<int>(log10(numeric

问题 I want to know if there is something in the standard, like a #define or something in numeric_limits which would tell me the maximum number of base-10 digits in the integral part of a floating point type. For example, if I have some floating point type the largest value of which is: 1234.567. I'd like something defined in the standard that would tell me 4 for that type. Is there an option to me doing this? template <typename T> constexpr auto integral_digits10 = static_cast<int>(log10(numeric

问题 I have a small program which compares (1) sizeof, (2) numeric_limits::digits, (3) and the results of a loop in an effort to make sure they all report the same thing regarding the size of the "int types" on any C++ implementation. However because I don't know about the internals of sizeof, I have to wonder if it is just reporting numeric_limits::digits. Thanks 回答1: Most likely sizeof() on most compilers causes the compiler to look the given type (or object's type) up in its internal type table

问题 In my application (compiled under Visual C++ 2010), I have code like this in a header file: // example.h #pragma once #include <limits> namespace myspace { // A generic equality test template<typename T> inline bool equal( const T &v1, const T &v2, const T &eps = std::numeric_limits<T>::epsilon()) { return (v1 == v2); } // Template specialization for floating-point numbers template<> bool equal<float>( const float &v1, const float &v2, const float &eps); // A generic equality test for finite

问题 I would like to define inside a class a constant which value is the maximum possible int. Something like this: class A { ... static const int ERROR_VALUE = std::numeric_limits<int>::max(); ... } This declaration fails to compile with the following message: numeric.cpp:8: error: 'std::numeric_limits::max()' cannot appear in a constant-expression numeric.cpp:8: error: a function call cannot appear in a constant-expression I understand why this doesn't work, but two things look weird to me: It