What good are typelists?

This is a discussion on What good are typelists? within the C++ Programming forums, part of the General Programming Boards category; Just a quick question, but I fail to see the point with typelists. The book mentions that a typelist is ...

  1. #1
    C++まいる!Cをこわせ! Elysia's Avatar
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    What good are typelists?

    Just a quick question, but I fail to see the point with typelists.
    The book mentions that a typelist is good for an abstract library which we want to abstract. Say:

    Code:
    class Library
    {
        virtual Window* CreateWindow() = 0;
        virtual Button* CreateButton() = 0;
        virtual ScrollBar* CreateScrollBar() = 0;
    };
    (Example from book [Modern C++ Design].)

    The book goes on about how to use and manipulate typelists, but never what they're good for and how they can be used to abstract this interface.
    Anyone have any good explanation or example?
    Last edited by Elysia; 06-27-2008 at 11:54 AM.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  2. #2
    Cat without Hat CornedBee's Avatar
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    The book introduces typelists early because they're a very fundamental utility used throughout the rest of the book. Just keep reading, and you'll find some applications.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

  3. #3
    C++まいる!Cをこわせ! Elysia's Avatar
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    I see. Well, there are yet some chapters to plow through.
    Thanks for the answer, though.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  4. #4
    Cat without Hat CornedBee's Avatar
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    Specifically, chapter 10 and 11 make heavy use of typelists.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

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    is it possible to use a typelist in conjunction with a variable argument function to disambiguate the types of the arguments passed to the function?

    i hope that makes sense.

  6. #6
    C++まいる!Cをこわせ! Elysia's Avatar
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    So far as I understand, it's a way to take a variable amount of types in a template declaration (or whatever it's called). Similar to variable arguments for functions.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  7. #7
    Cat without Hat CornedBee's Avatar
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    Quote Originally Posted by m37h0d View Post
    is it possible to use a typelist in conjunction with a variable argument function to disambiguate the types of the arguments passed to the function?

    i hope that makes sense.
    Yes, but it's a mess to implement, and the restrictions on varargs still apply - i.e., PODs only.
    All the buzzt!
    CornedBee

    "There is not now, nor has there ever been, nor will there ever be, any programming language in which it is the least bit difficult to write bad code."
    - Flon's Law

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