Deducing Function Template Arguments

This is a discussion on Deducing Function Template Arguments within the C++ Programming forums, part of the General Programming Boards category; Hello everyone, Here is my understanding of what Bjarne said in his The C++ Programming Language book. I am not ...

  1. #1
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    Deducing Function Template Arguments

    Hello everyone,


    Here is my understanding of what Bjarne said in his The C++ Programming Language book. I am not sure whether my understanding is correct? I am somewhat confused about the following statements.

    My understanding is,

    means if a function call like this,

    Code:
    void func(const A a) // A is a specific type
    then compiler can deduce argument type of template function below to A?

    Code:
    template <class T> func (T a)
    Bjarne's original statements are,

    --------------------
    C.13.4 Deducing Function Template Arguments

    A compiler can deduce a type template argument, T or TT , and a nontype
    template argument, I, from a template function argument with a type composed of the following constructs:

    Code:
    T const T volatile T
    T*  T& T[constant_expression]
    type[I]  class_template_name<T> class_template_name<I>
    T T<T > T<I > T<>
    --------------------


    thanks in advance,
    George

  2. #2
    Cat without Hat CornedBee's Avatar
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    means if a function call like this,
    That's not a function call. That's a head. Add a semicolon, it's a prototype. Add braces, it's an implementation.
    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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    Sorry CornedBee,


    My bad. :-)

    If I change to the following in my original post, do you think my
    understanding is correct?

    Code:
    const A a; // A is a specific type
    func(a); // can deduce T to A.
    Quote Originally Posted by CornedBee View Post
    That's not a function call. That's a head. Add a semicolon, it's a prototype. Add braces, it's an implementation.

    regards,
    George

  4. #4
    C++まいる!Cをこわせ!
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    Yes, it can. So long as you don't pass unambiguous types, the compiler can deduce the type.
    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.

  5. #5
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    Thanks Elysia,


    Question answered.

    Quote Originally Posted by Elysia View Post
    Yes, it can. So long as you don't pass unambiguous types, the compiler can deduce the type.

    regards,
    George

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