Selecting datatype at runtime

hkn · #1 22-Jan-2009, 04:11

Hello,

is it possible to choose the type of variable at runtime in c++

for example

CPP / C++ / C Code:

void func(int x)
{
    if(x == 1)
    {
         double y;
    }
    elseif(x== 2)
    {
         int y;
    }
    else
    {
         float y;
    }
    
}

or actually I want to define a templated variable with different types according to the input in a function

CPP / C++ / C Code:

func(int x)
{
     if( x == 0)
          templatedvariable<int> y = new templatedvariable<int>();
     else
          templatedvariable<double> y = new templatedvariable<double>();
}

Mexican Bob · #2 22-Jan-2009, 06:14

Template types are known at compile time and are probably not what you really want.

You may want to explore RTTI (runtime type information). However, it is unclear what you really want to do based on the information that you've provided. Your example, even if successful doesn't do anything meaningful, so it is useless. Useless in what it "does" (if it worked) and useless at conveying your real meaning.

If you mean to say that you want to pass in a variable that describes the "type information," to a function and have it return a new instance of the type, fine. What you've described can be implemented in a few different ways. the VARIANT type popular in Visual Basic is a good example of how to implement such a beast. In C it is implemented using a union of several types and, of course, an identifier that identifies the type to "the world."

How about rephrasing what you want and add perhaps more about what you want to do with it so that we'll better know how to respond?

MxB

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Selecting datatype at runtime

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