《STL源码剖析》---stl_numeric.h阅读笔记

stl_numeric.h里面的都是数值算法，与数值计算有关。

G++ 2.91.57，cygnus\cygwin-b20\include\g++\stl_numeric.h 完整列表/* * * Copyright (c) 1994 * Hewlett-Packard Company * * Permission to use, copy, modify, distribute and sell this software * and its documentation for any purpose is hereby granted without fee, * provided that the above copyright notice appear in all copies and * that both that copyright notice and this permission notice appear * in supporting documentation.  Hewlett-Packard Company makes no * representations about the suitability of this software for any * purpose.  It is provided "as is" without express or implied warranty. * * * Copyright (c) 1996,1997 * Silicon Graphics Computer Systems, Inc. * * Permission to use, copy, modify, distribute and sell this software * and its documentation for any purpose is hereby granted without fee, * provided that the above copyright notice appear in all copies and * that both that copyright notice and this permission notice appear * in supporting documentation.  Silicon Graphics makes no * representations about the suitability of this software for any * purpose.  It is provided "as is" without express or implied warranty. *//* NOTE: This is an internal header file, included by other STL headers. *   You should not attempt to use it directly. */#ifndef __SGI_STL_INTERNAL_NUMERIC_H#define __SGI_STL_INTERNAL_NUMERIC_H__STL_BEGIN_NAMESPACE//计算init和[first last)区间元素的和// 版本一template <class InputIterator, class T>T accumulate(InputIterator first, InputIterator last, T init) {  for ( ; first != last; ++first)    init = init + *first; // 每个元素的初值累加到init上  return init;}// 版本二template <class InputIterator, class T, class BinaryOperation>T accumulate(InputIterator first, InputIterator last, T init,                BinaryOperation binary_op) {  for ( ; first != last; ++first)    init = binary_op(init, *first);//  对每一个元素执行二元操作  return init;}//计算两段元素的内积，要提供初始值init。两段元素一样长，所以第二段没提供last2// 版本一template <class InputIterator1, class InputIterator2, class T>T inner_product(InputIterator1 first1, InputIterator1 last1,                   InputIterator2 first2, T init) {  for ( ; first1 != last1; ++first1, ++first2)    init = init + (*first1 * *first2); // 执行两个序列的一般內積  return init;}// 版本二template <class InputIterator1, class InputIterator2, class T,          class BinaryOperation1, class BinaryOperation2>T inner_product(InputIterator1 first1, InputIterator1 last1,                   InputIterator2 first2, T init, BinaryOperation1 binary_op1,                   BinaryOperation2 binary_op2) {  for ( ; first1 != last1; ++first1, ++first2)// 以外界提供的仿函数来取代第一版本中的 operator* 和 operator+。// op2 作用域两元素间，op1用于op2之结果与init之间。    init = binary_op1(init, binary_op2(*first1, *first2));  return init;}//__partial_sum定义在partial_sum前面，后者调用前者template <class InputIterator, class OutputIterator, class T>OutputIterator __partial_sum(InputIterator first, InputIterator last,                                   OutputIterator result, T*) {  T value = *first;  while (++first != last) {    value = value + *first; // 前n个元素的总和    *++result = value;// 指定给目的端  }  return ++result;}// 版本一template <class InputIterator, class OutputIterator>OutputIterator partial_sum(InputIterator first, InputIterator last,                                OutputIterator result) {  if (first == last) return result;  *result = *first;  return __partial_sum(first, last, result, value_type(first));  // 侯捷认为（并证实证），不需像上行那样转呼叫，可改用以下写法（整个函式）：  // if (first == last) return result;  // *result = *first;  // iterator_traits<InputIterator>::value_type value = *first;  // while (++first != last) {  //   value = value + *first;  //   *++result = value;  // }  // return ++result;  // 这样的观念和作法，适用于本当所有函数}template <class InputIterator, class OutputIterator, class T,          class BinaryOperation>OutputIterator __partial_sum(InputIterator first, InputIterator last,                                  OutputIterator result, T*,                                  BinaryOperation binary_op) {  T value = *first;  while (++first != last) {    value = binary_op(value, *first);    *++result = value;  }  return ++result;}// 版本二template <class InputIterator, class OutputIterator, class BinaryOperation>OutputIterator partial_sum(InputIterator first, InputIterator last,                                OutputIterator result, BinaryOperation binary_op) {  if (first == last) return result;  *result = *first;  return __partial_sum(first, last, result, value_type(first), binary_op);  //  侯捷认为（并证实证），不需像上行那样转呼叫，可改用以下写法（整个函式）：  // if (first == last) return result;  // *result = *first;  // iterator_trait<InputIterator>::value_type value = *first;  // while (++first != last) {  //   value = binary_op(value, *first);  //   *++result = value;  // }  // return ++result;  //  //  这样的观念和作法，适用于本当所有函数}template <class InputIterator, class OutputIterator, class T>OutputIterator __adjacent_difference(InputIterator first, InputIterator last,                                             OutputIterator result, T*) {  T value = *first;  while (++first != last) {// 走过整个范围    T tmp = *first;    *++result = tmp - value;// 将两个相邻元素的差额（后-前），指派给目的端    value = tmp;  }  return ++result;}// 版本一template <class InputIterator, class OutputIterator>OutputIterator adjacent_difference(InputIterator first, InputIterator last,                                           OutputIterator result) {  if (first == last) return result;  *result = *first;// 首先记录第一个元素  return __adjacent_difference(first, last, result, value_type(first));}template <class InputIterator, class OutputIterator, class T,           class BinaryOperation>OutputIterator __adjacent_difference(InputIterator first, InputIterator last,                                             OutputIterator result, T*,                                            BinaryOperation binary_op) {  T value = *first;  while (++first != last) {    T tmp = *first;    *++result = binary_op(tmp, value); // 将相邻两元素的运算結果，指派给目的端    value = tmp;  }  return ++result;}// 版本二template <class InputIterator, class OutputIterator, class BinaryOperation>OutputIterator adjacent_difference(InputIterator first, InputIterator last,                                          OutputIterator result,                                          BinaryOperation binary_op) {  if (first == last) return result;  *result = *first;  return __adjacent_difference(first, last, result, value_type(first),                                     binary_op);}//power为SGI专属，并不在STL标准之列，它用来计算某数的n幂次方。//这里所谓的n幂次方是指对自己进行某种运算n次，运算类型可由外界执行。如果是乘法则就是乘幂。// 版本二，冪次方。如果指定为乘法运算，则当n >= 0 时传回 x ** n。// 注意，"multiplication" 必须满足结合律（associative），//  但不需满足交换律（commutative）。template <class T, class Integer, class MonoidOperation>T power(T x, Integer n, MonoidOperation op) {  if (n == 0)    return identity_element(op);// 取出「证同元素」identity element.证同元素在后面章节介绍  else {    while ((n & 1) == 0) {      n >>= 1;      x = op(x, x);//两个参数都是x。因为每次n减小1倍(n是偶数，因为n&1=0)    }    T result = x;    n >>= 1;    while (n != 0) {      x = op(x, x);      if ((n & 1) != 0)        result = op(result, x);      n >>= 1;    }    return result;  }}// 版本一，乘冪。template <class T, class Integer>inline T power(T x, Integer n) {  return power(x, n, multiplies<T>());}// 侯捷：iota 是什麼的缩写？// 函数意义：在 [first,last) 范围内內填入value, value+1, value+2...。template <class ForwardIterator, class T>void iota(ForwardIterator first, ForwardIterator last, T value) {  while (first != last) *first++ = value++;}__STL_END_NAMESPACE#endif /* __SGI_STL_INTERNAL_NUMERIC_H */// Local Variables:// mode:C++// End: