Q157220: INFO: STL Sample for the exp, log, and log10 Functions
Article: Q157220
Product(s): Microsoft C Compiler
Version(s): 4.2,5.0,6.0
Operating System(s):
Keyword(s): kbcode kbVC420 kbVC500 kbVC600 kbDSupport
Last Modified: 27-MAR-2002
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The information in this article applies to:
- The Standard C++ Library, used with:
- Microsoft Visual C++, 32-bit Enterprise Edition, versions 4.2, 5.0, 6.0
- Microsoft Visual C++, 32-bit Professional Edition, versions 4.2, 5.0, 6.0
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0
- Microsoft Visual C++.NET (2002)
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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.
//////////////////////////////////////////////////////////////////////
// disable warning C4267: possible loss of data,
// okay to ignore
#pragma warning(disable: 4267)
#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.size() << "\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
Technology : kbVCsearch kbAudDeveloper kbVCLibrary
Version : :4.2,5.0,6.0
Issue type : kbinfo
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