Solved

complex number

Posted on 1999-01-24
3
268 Views
Last Modified: 2010-04-02
this question goes out t othose who have experience in BCB3.
recently, i tried to used the complex class in a SDI application. i declared a variable like this:

#include <complex.h>
complex EM;

the complier gave an error message :"illegal use of template."
Whats wrong ?
can someone pls explained.
0
Comment
Question by:deuter
  • 2
3 Comments
 
LVL 31

Accepted Solution

by:
Zoppo earned 100 total points
ID: 1185041
I do not know BCB3, but I know that complex is a template class needing a type as parameter like this:

#include <complex.h>
complex <float> EM;   // create a complex using floats
complex <double> EM_1;   // create a complex using doubles

Explanation:
copmlex is defined as template like this:
------------------------------------------------------------
template<class T> class complex
{
    public:    typedef T value_type;
// and so on ...
------------------------------------------------------------
This tells the compiler to create a own class complex for any type with which it's used (thats the sense of templates).

so you must declare the type !!


hope that help,

ZOPPO
0
 

Author Comment

by:deuter
ID: 1185042
zoppo, thanks for the explanation, can you show me where i can get more info for the template?
0
 
LVL 31

Expert Comment

by:Zoppo
ID: 1185043
I think you just will have to buy a good C++ book to learn more about templates. I can give you a short description:

the expression 'template <class T(,...)>' before a class or function definition tells the compiler to create one class/function for each different type used.

For example:

template <class T> class X // example of a simple template class X
{
public:
typedef T calue_type;

value_type m_data;
void SetData( value_type data ) { m_data = data };
value_type GetData( void ){ return m_data };
.
}

template <class T> T mymin( T w1, T w2 ) // template function mymin
{
if ( w1 < w2 )
   return w1;
else
   return w2;
}

X<char> x_char;               // creates a class X with value_type char
X<double> x_double;        // creates a class X with value_type double
X<CString> x_string;        // creates a class X with value_type CString

int i = mymin( 5, 3 );        // create a call to a funtion 'int mymin( int 5, int 3 );' - returns 3
double d = mymin( 5.3, 7.4 );      // create a call to a funtion 'double mymin( double, double );' - returns 5.2
CString test = mymin( "world", "Hello, " );  // create a call to a funtion CString mymin( CString, CString );' - returns "Hello, world"

that not a good explanaition, but it's all I ever needed to know. But allthough I think it's good to have a good C++ book to learn this more detailed.

hope that helps,

ZOPPO
0

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Cross compile release version of c++ program for linux 2 136
Find Visual Studio Tools 2 113
Dynamically allocate memory 9 65
VS2015 Redefinition errors 4 73
Many modern programming languages support the concept of a property -- a class member that combines characteristics of both a data member and a method.  These are sometimes called "smart fields" because you can add logic that is applied automaticall…
This article shows you how to optimize memory allocations in C++ using placement new. Applicable especially to usecases dealing with creation of large number of objects. A brief on problem: Lets take example problem for simplicity: - I have a G…
The viewer will learn how to use the return statement in functions in C++. The video will also teach the user how to pass data to a function and have the function return data back for further processing.
The viewer will be introduced to the technique of using vectors in C++. The video will cover how to define a vector, store values in the vector and retrieve data from the values stored in the vector.

820 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question