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 如何查看各个类型的最大值 收藏
问题源于同事的一个问题，VC编译器里如何查看double的最大值? 他在limits.h里没找到。

在limits.h里面，只可以看到整型的最大值，但是看不到浮点数的最大值。浮点数的最大值可以这样得到:

#include <iostream>

#include <limits>

using namespace std;

// compile with: /EHscint main(){

   cout << numeric_limits<double>::max() << endl; 

}

运行平台为VS2008,如果出现max编译冲突，可以加上#undef max。

模板类numeric_limits的声明是:

template <typename T>

numeric_limits<T>

// 变量和成员函数
//
//    has_denorm
//    has_denorm_loss
//    has_infinity
//    has_quiet_NaN
//    has_signaling_NaN
//    is_bounded
//    is_exact
//    is_iec559
//    is_integer
//    is_modulo
//    is_signed
//    is_specialized
//    tinyness_before
//    traps
//    round_style
//    digits
//    digits10
//    max_exponent
//    max_exponent10
//    min_exponent
//    min_exponent10
//    radix;
//    denorm_min()
//    epsilon()
//    infinity()
//    max()
//    min()
//    quiet_ NaN()
//    round_error()
//    signaling_NaN()
//////////////////////////////////////////////////////////////////////
实例代码：#include <iostream>
#include <limits>

using namespace std;

int main() {
    cout << " 1 The minimum value for char is " <<
        (int)numeric_limits<char>::min() << endl;
    cout << " 2 The minimum value for int is  " <<
        numeric_limits<int>::min() << endl;
    cout << " 3 The maximum value for char is " <<
        (int)numeric_limits<char>::max() << endl;
    cout << " 4 The maximum value for int is  " <<
        numeric_limits<int>::max() << endl;
    cout << " 5 The number of bits to represent a char is " <<
        numeric_limits<char>::digits << endl;
    cout << " 6 The number of bits to represent an int is " <<
        numeric_limits<int>::digits << endl;
    cout <<" 7 The number of digits representable in base 10 for float is "
         << numeric_limits<float>::digits10 << endl;
    cout << " 8 Is a char signed?              " <<
        numeric_limits<char>::is_signed << endl;
    cout << " 9 Is an unsigned integer signed? " <<
        numeric_limits<unsigned int>::is_signed << endl;
    cout << "10 Is an integer an integer? " <<
        numeric_limits<int>::is_integer << endl;
    cout << "11 Is a float an integer?   " <<
        numeric_limits<float>::is_integer << endl;
    cout << "12 Is an integer exact? " <<
        numeric_limits<int>::is_exact << endl;
    cout << "13 Is a float exact?  " <<
        numeric_limits<float>::is_exact << endl;
    cout << "14 The radix for float is            "  <<
        numeric_limits<float>::radix << endl;
    cout << "15 The epsilon for float is          " <<
        numeric_limits<float>::epsilon() << endl;
    cout << "16 The round error for float is      " <<
        numeric_limits<float>::round_error() << endl;
    cout << "17 The minimum exponent for float is " <<
        numeric_limits<float>::min_exponent << endl;
    cout << "18 The minimum exponent in base 10   " <<
        numeric_limits<float>::min_exponent10 << endl;
    cout << "19 The maximum exponent is           " <<
        numeric_limits<float>::max_exponent << endl;
    cout << "20 The maximum exponent in base 10   " <<
        numeric_limits<float>::max_exponent10 << endl;
    cout << "21 Can float represent positive infinity?  " <<
        numeric_limits<float>::has_infinity << endl;
    cout << "22 Can double represent positive infinity? " <<
        numeric_limits<double>::has_infinity << endl;
    cout << "23 Can int represent positive infinity? " <<
        numeric_limits<int>::has_infinity << endl;
    cout << "24 Can float represent a NaN?           " <<
        numeric_limits<float>::has_quiet_NaN << endl;
    cout << "25 Can float represent a signaling NaN? " <<
        numeric_limits<float>::has_signaling_NaN << endl;
    cout << "26 Does float allow denormalized values?   " <<
        numeric_limits<float>::has_denorm << endl;
    cout << "27 Does float detect denormalization loss? " <<
        numeric_limits<float>::has_denorm_loss << endl;
    cout << "28 Representation of positive infinity for float " <<
        numeric_limits<float>::infinity() << endl;
    cout << "29 Representation of quiet NaN for float         " <<
        numeric_limits<float>::quiet_NaN() << endl;
    cout << "30 Minimum denormalized number for float         " <<
        numeric_limits<float>::denorm_min() << endl;
    cout << "31 Minimum positive denormalized value for float " <<
        numeric_limits<float>::denorm_min() << endl;
    cout << "32 Does float adhere to IEC 559 standard?  " <<
        numeric_limits<float>::is_iec559 << endl;
    cout << "33 Is float bounded? " <<
        numeric_limits<float>::is_bounded << endl;
    cout << "34 Is float modulo?  " <<
        numeric_limits<float>::is_modulo << endl;
    cout << "35 Is int modulo?    " <<
        numeric_limits<float>::is_modulo << endl;
    cout << "36 Is trapping implemented for float?    " <<
        numeric_limits<float>::traps << endl;
    cout << "37 Is tinyness detected before rounding? " <<
        numeric_limits<float>::tinyness_before << endl;
    cout << "38 What is the rounding style for float? " <<
        (int)numeric_limits<float>::round_style << endl;
    cout << "39 What is the rounding style for int? " <<
        (int)numeric_limits<int>::round_style << endl;
    cout << "40 How does a float represent a signaling NaN? " <<
        numeric_limits<float>::signaling_NaN() << endl;
    cout << "41 Is int specialized? " <<
        numeric_limits<float>::is_specialized << endl;
}请运行相关的代码查看结果。

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