INFO: STL Sample for the exp, log, and log10 Functions
ID: Q157220
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The information in this article applies to:
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The Standard C++ Library, used with:
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Microsoft Visual C++, 32-bit Editions, versions 4.2, 5.0, 6.0
SUMMARY
The sample code below illustrates how to use the exp, log, and log10 STL
functions in Visual C++.
MORE INFORMATION
Required Header
<valarray>
<math>
Prototype
/ exp
template<class T>
valarray<T> exp(const valarray<T>& x);
// log
template<class T>
valarray<T> log(const valarray<T>& x);
// log10
template<class T>
valarray<T> log10(const valarray<T>& x);
NOTE: The class/parameter names in the prototype may not match the version
in the header file. Some have been modified to improve readability.
Description
This article illustrates the use of STL exp(), log(), and log10() functions
through sample code.
Sample Code
//////////////////////////////////////////////////////////////////////
//
// Compile options needed: None
//
// <filename> : main.cpp
//
// Functions:
//
// exp, log, log10
//
// Written by Yeong-Kah Tam
// of Microsoft Product Support Services,
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
//////////////////////////////////////////////////////////////////////
#include <iostream> // for i/o functions
#include <valarray> // for valarray
#include <math.h> // for exp(), log(), and log10()
#if _MSC_VER > 1020 // if VC++ version is > 4.2
using namespace std; // std c++ libs implemented in std
#endif
#define ARRAY_SIZE 3 // array size
typedef valarray<double> DB_VARRAY;
void main()
{
// Set val_array to contain values 1, 10, 100 for the following test.
DB_VARRAY val_array(ARRAY_SIZE);
for (int i = 0; i < ARRAY_SIZE; i++)
val_array[i] = pow(10, i);
// Display the size of val_array.
cout << "Size of val_array = " << val_array.length() << "\r\n";
// Display the content of val_array before calling exp, log, and
// log10 functions.
cout << "The values in val_array:\r\n";
for (i = 0; i < ARRAY_SIZE; i++)
cout << val_array[i] << " ";
cout << "\r\n\r\n";
// rvalue_array to hold the return value from calling the sqrt() and
// pow() functions.
DB_VARRAY rvalue_array;
// ----------------------------------------------------------------
// exp() - display the content of rvalue_array
// ----------------------------------------------------------------
rvalue_array = exp(val_array);
cout << "The result after calling exp():\r\n";
for (i = 0; i < ARRAY_SIZE; i++)
cout << rvalue_array[i] << " ";
cout << "\r\n\r\n";
// ----------------------------------------------------------------
// log() - display the content of rvalue_array
// ----------------------------------------------------------------
rvalue_array = log(val_array);
cout << "The result after calling log():\r\n";
for (i = 0; i < ARRAY_SIZE; i++)
cout << rvalue_array[i] << " ";
cout << "\r\n\r\n";
// ----------------------------------------------------------------
// log10() - display the content of rvalue_array
// ----------------------------------------------------------------
rvalue_array = log10(val_array);
cout << "The result after calling log10():\r\n";
for (i = 0; i < ARRAY_SIZE; i++)
cout << rvalue_array[i] << " ";
cout << "\r\n\r\n";
}
Output:
Size of val_array = 3
The values in val_array:
1 10 100
The result after calling exp():
2.71828 22026.5 2.68812e+043
The result after calling log():
0 2.30259 4.60517
The result after calling log10():
0 1 2
REFERENCES
Visual C++ Books On Line: Visual C++ Books:C/C++:Standard C++ Library
Reference.
Additional query words:
STL STLSample exp log log10
Keywords : kbcode kbVC420 kbVC500 kbVC600 kbDSupport STLIss
Version : winnt:4.2,5.0,6.0
Platform : winnt
Issue type : kbinfo