Skip to main content
pointer cause decay, references do not.

Decay means loss of type information. In C and C++, an array name 'decays' to pointer to the first element. The information lost is basically the number of elements in the array. This difference should be manifested by sizeof() operator in function f() and g(). References keep that information with them. such as 'constness' of int. Function names are also said to 'decay' into pointer to the function if only function name is used. But such a function pointer retains, I think, everything about the function signature: parameter types and function return type; even in C.

With following declarations,

template < typename T > void f (T);
template < typename T > void g (T &);

and with these declarations,

double x[20];
int const seven = 7;

f(x); T is double *
g(x); T is double [20]
f(seven); T is int
g(seven); T is int const
f(7); T is int
g(7); T is int, ERROR can't pass 7 to int&

Therefore, pointer cause decay, references do not.
source: C++ Templates - The Complete Guide
by David Vandevoorde and Nicolai M. Josuttis

Comments

Extraordinary blog. Your site was hip and fresh
and we'll visit it again! I love surfing the internet
for blogs.
I want you to stop and compare with my 1800contacts coupon blog.
Great blog. I surf the web looking for blogs like
this. Your site was on point and will be back again!
No matter when you are, just stop by and check for my 1800contacts com coupon blog site.
Inspiring blog. I love finding blogs this good on
the internet, when I have the time. I'm going to go
back to it!
It may look like it was hard work, but my blog was simple.
Striking blog. I liked the site I will be back
again! Websurfing is a good way to find blogs like
yours.
I can't explain, but you need to check my 1800contacts web coupon code blog!
Excellent blog. Your site was great and will be
finding it again!  I surf the net for blogs like
yours.
In my spare time I will look for your coupon codes 1800contacts blog.
lightly-blended said…
Exciting blog. The site out did itself and will be
back! I love surfing the internet for blogs that are
exactly like this blog.
Everyday of the month you need to peep my 1800contacts com coupon blog.
Incredible blog. I admired your site and I will be
back once again to view it! I use much of my spare
time searching for blogs like yours.
I want you to look for my coupon codes 1800contacts blog.
Unique blog my friend, I can hardly wait to vist
this site again. I just worship the site its comes
from! Believe me in my extra time I'm consistently
looking up blogs like this.
My blog, is something you need to peep out!
condensed said…
Hype blog. And I admire your site and plan on
returning to it! When I web surf it always helps me to
find great blogs.
Please go over my blog.
Hype blog. And I admire your site and plan on
returning to it! When I web surf it always helps me to
find great blogs.
My 1800contacts com coupon blog, is something you need to peep out!

Popular posts from this blog

Multi-dimensional arrays in C++11

What new can be said about multi-dimensional arrays in C++? As it turns out, quite a bit! With the advent of C++11, we get new standard library class std::array. We also get new language features, such as template aliases and variadic templates. So I'll talk about interesting ways in which they come together.

It all started with a simple question of how to define a multi-dimensional std::array. It is a great example of deceptively simple things. Are the following the two arrays identical except that one is native and the other one is std::array?

int native[3][4];
std::array<std::array<int, 3>, 4> arr;

No! They are not. In fact, arr is more like an int[4][3]. Note the difference in the array subscripts. The native array is an array of 3 elements where every element is itself an array of 4 integers. 3 rows and 4 columns. If you want a std::array with the same layout, what you really need is:

std::array<std::array<int, 4>, 3> arr;

That's quite annoying for two r…

Folding Monadic Functions

In the previous two blog posts (Understanding Fold Expressions and Folding Functions) we looked at the basic usage of C++17 fold expressions and how simple functions can be folded to create a composite one. We’ll continue our stride and see how "embellished" functions may be composed in fold expressions.

First, let me define what I mean by embellished functions. Instead of just returning a simple value, these functions are going to return a generic container of the desired value. The choice of container is very broad but not arbitrary. There are some constraints on the container and once you select a generic container, all functions must return values of the same container. Let's begin with std::vector.
// Hide the allocator template argument of std::vector. // It causes problems and is irrelevant here. template <class T> struct Vector : std::vector<T> {}; struct Continent { }; struct Country { }; struct State { }; struct City { }; auto get_countries…

Covariance and Contravariance in C++ Standard Library

Covariance and Contravariance are concepts that come up often as you go deeper into generic programming. While designing a language that supports parametric polymorphism (e.g., templates in C++, generics in Java, C#), the language designer has a choice between Invariance, Covariance, and Contravariance when dealing with generic types. C++'s choice is "invariance". Let's look at an example.
struct Vehicle {}; struct Car : Vehicle {}; std::vector<Vehicle *> vehicles; std::vector<Car *> cars; vehicles = cars; // Does not compile The above program does not compile because C++ templates are invariant. Of course, each time a C++ template is instantiated, the compiler creates a brand new type that uniquely represents that instantiation. Any other type to the same template creates another unique type that has nothing to do with the earlier one. Any two unrelated user-defined types in C++ can't be assigned to each-other by default. You have to provide a c…