sqrt 和 pow
在 Visual C++ 演示如何使用 sqrt 和 pow 标准 (STL)模板库函数。
template<class T>
inline valarray<T> sqrt(
const valarray<T>& x
);
template<class T>
inline valarray<T> pow(
const valarray<T>& x,
const valarray<T>& y
);
template<class T>
inline valarray<T> pow(
const valarray<T> x,
const T& y
);
template<class T>
inline valarray<T> pow(
const T& x,
const valarray<T>& y
);
备注
备注
类/参数名在原型不匹配版本在头文件。修改某些提高可读性。
sqrt 返回类 valarrayAMP_LTTAMP_GT 对象，每一个在索引 I 的元素 x为 []I平方根。 pow 有三个模板函数。 第一个模板函数返回类 valarrayAMP_LTTAMP_GT 对象，每一个在索引 I 的元素 x为 []I引发的 y[]I的能力。 元素的 I xI[] 第二个模板函数存储引发的 y. 的功能。 元素中的第三个模板函数存储 我 x 引发的 y[]I的能力。
示例
// sqrtpow.cpp
// compile with: /EHsc
#include <iostream> // for i/o functions
#include <valarray> // for valarray
#include <cmath> // for sqrt() and pow()
using namespace std ;
#define ARRAY_SIZE 3 // array size
int main()
{
// Set val_array to contain values 1, 4, 9 for the following test
valarray<double> val_array(ARRAY_SIZE);
int i;
for (i = 0; i < ARRAY_SIZE; i++)
val_array[i] = (i+1) * (i+1);
// Display the size of val_array
cout << "Size of val_array = " << val_array.size() << endl;
// Display the values of val_array before calling sqrt() and pow().
cout << "The values in val_array:" << endl << "[";
for (i = 0; i < ARRAY_SIZE; i++)
cout << " " << val_array[i];
cout << " ]" << endl << endl;
// Initialize rev_valarray that is the reverse of val_array.
valarray<double> rev_valarray(ARRAY_SIZE);
for (i = 0; i < ARRAY_SIZE; i++)
rev_valarray[i] = val_array[ARRAY_SIZE - i - 1];
// Display the size of rev_valarray.
cout << "Size of rev_valarray = " << rev_valarray.size() << endl;
// Display the values of rev_valarray.
cout << "The values in rev_valarray:" << endl << "[";
for (i = 0; i < ARRAY_SIZE; i++)
cout << " " << rev_valarray[i];
cout << " ]" << endl << endl;
// rvalue_array to hold the return value from calling the sqrt() and
// pow() functions.
valarray<double> rvalue_array;
// ----------------------------------------------------------------
// sqrt() - display the content of rvalue_array
// ----------------------------------------------------------------
// Display the result of val_array after calling sqrt().
rvalue_array = sqrt(val_array);
cout << "The result of val_array after calling sqrt():"
<< endl << "[";
for (i = 0; i < ARRAY_SIZE; i++)
cout << " " << rvalue_array[i];
cout << " ]" << endl << endl;
// ----------------------------------------------------------------
// pow() - display the content of rvalue_array
// ----------------------------------------------------------------
// This template function returns an object of class valarray<T>,
// each of whose elements at I is x[I] raised to the power of y[I].
rvalue_array = pow(val_array, rev_valarray);
cout << "The result after calling pow(val_array, rev_valarray):"
<< endl << "[";
for (i = 0; i < ARRAY_SIZE; i++)
cout << " " << rvalue_array[i];
cout << " ]" << endl << endl;
// This template function stores in element I x[I] raised to the
// power of y, where y=2.0.
rvalue_array = pow(val_array, 2.0);
cout << "The result after calling pow(val_array, 2.0):"
<< endl << "[";
for (i = 0; i < ARRAY_SIZE; i++)
cout << " " << rvalue_array[i];
cout << " ]" << endl << endl;
// This template function stores in element I x raised to the
// y[I] power, where x=2.0.
rvalue_array = pow(2.0, val_array);
cout << "The result after calling pow(2.0, val_array):"
<< endl << "[";
for (i = 0; i < ARRAY_SIZE; i++)
cout << " " << rvalue_array[i];
cout << " ]" << endl;
}
Output
Size of val_array = 3
The values in val_array:
[ 1 4 9 ]
Size of rev_valarray = 3
The values in rev_valarray:
[ 9 4 1 ]
The result of val_array after calling sqrt():
[ 1 2 3 ]
The result after calling pow(val_array, rev_valarray):
[ 1 256 9 ]
The result after calling pow(val_array, 2.0):
[ 1 16 81 ]
The result after calling pow(2.0, val_array):
[ 2 16 512 ]
要求
**标题:**valarray