assign generic type of variables in a function

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Hello everyone,
How can i be able to make a function be assigned with a generic type parameter in C
for example in order to get the length of an array i use the following,

C++

int n;
n = (sizeof(array)/ sizeof(array[0]));

i find this statement useful and i want to put it in a generic function, but an array can be of any type, how to make the function receive any 1D array of any type.

Thanks in advance,
z3ngew

Posted 28-Aug-13 11:30am

z3ngew

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2 solutions

Solution 3

your solution is perfect but ansi c does not support

C++

template

so here is the solution in c

C++

#define ARRAY_SIZE(x)  (sizeof(x) / sizeof(x[0]))

you can pass any type of array in this function,
Thanks for your effort everyone,

z3ngew

Posted 31-Aug-13 6:09am

z3ngew

Comments

Philippe Mori 1-Sep-13 8:38am

Well, although you mention C in the question, it was also tagged as C++ and you were taking about generic functions which make us think you want a template function.

With the C macro, you just have to be careful to use it only when it can be used (array with compile-time known size).

In pratice, it might offten be preferable to declare a constant and used that constant instead. const int n =5; int x[n]; particulary if you need to declare multiple arrays of that same size.

z3ngew 1-Sep-13 12:28pm

I'm sry for the confusion, and about using a constant, it really solve it perfectly but sometimes you just need to return the length of the array without declaring it previously.

Thanks for your effort,

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Philippe Mori · Accepted Answer · 2013-08-28T17:30:00

Assuming that by array, you are talking about traditionnal C style array like this one:

C++

int anArray[25];

If you don't need compile-time value, then the following function will be able to evaluate the number of items in any array.

C++

template <typename T, int n> int len(T(&array)[n])
{
    return (sizeof(array)/ sizeof(array[0]));
}

You can then get the length like that:

C++

int n = len(anArray);

Since that code will only compile for arrays and not pointers, the template is safer to uses as it would not compile with pointers (or the equivalent int not_really_an_array[]).

Also, in the Template function, one could simply write return n; but I have copied the original code (including all superfluous parenthesis) to make it clear that I do same thing.