Passing array as argument of a function in C++

Question

How can I pass an array as argument of a function in C++? Is it efficient?

Answer 1

@Marius there is not much to clarify..
It's a very used trick, in C++ you'd better use std::vector.

this trick consist of templates mixed whit size_t special features.
make it simpler..
template<size_t size> // this will capture the size of your arr
doSomething(int(&arr)[size])//the size obj of class size_t captures the size of the array passed..
{
for(size_t i =0;i <size;++i){
...

so when you call this function..
int someData[]={1,2,3,4};
doSomething(someData);//you don't have to pass the size, size_t class do the dirty job for you!

Answer 2

Try this..

template <typename T, size_t size>
myFunc( T(&array)[size]){.....definition...}

hope it helps :)

Answer 3

Here's a simple example, here we pass intArray (array of int) to the getValue function, which iterates the array to find a value (needle) and return it if found.

I'm not sure what you mean by efficient, imo code efficiency lies in the coder's hand, rather than what was used.

#include <iostream>

int getValue(int arr[], int needle, int itemCount)
{
for(int i = 0; i < itemCount; ++i)
{
if(arr[i] == needle) return arr[i];
}
return 0;
}

int main()
{
int intArray[] {1,2,3,4,5,6,7,8,9,10};
std::cout << getValue(intArray, 7, 10);

return 0;
}

Hth, cmiiw

Answer 4

A.) void func(int *arr) - pointer
B.) void func(int arr[]) - unsized array
C.) void func(int arr[10]) - sized array

All three are called the same way syntactically like this:
int main()
{
int arr[] = {1,2,3,4,5,6,7,8,9,10};
func(arr); // or
func(&arr[0]);
}

The C++ compiler will not do out-of-bounds checking.

All accomplish the same and are efficient. They all result as the parameter being passed as a pointer to the first element.

Just to clarify, none of these copy the array data itself when passing it.

Answer 5

When you pass a pointer to an array, you should also pass the size of the array

void func(int * arr, int size) {}

Otherwise there's no way the function can know how big the array is - let me just say "Index out of bound".
Except if your array size is a global constant, of course.

Answer 6

AZTECCO I am sure that is going to clarify everything up for Dany Abreu 😆

Answer 7

Hi Marius, thanks for your answer! Could you explain me the entire process? How I can receive the pointer and use it in my function?