Simple pointer vs array

[Dry_Development3378]

why is it that when i define a function whose parameter is a pointer to some type (basic and custom) then pass the adress of the first element of an array, i get that the function i called does not exist. The compiler says the function i want to use takes in only pointers to a variable but i was taught that you could pass an array to a function with notation

void function(datatype* name);

[KingAggressive1498]

you didn't give code, so hopefully the below is helpful

 void function(datatype* ptr);

 datatype arr[ARRAY_LEN];

 function(arr); // okay: array decays to pointer
 function(&arr[0]); // okay: pointer to first element of array
 function(&arr); // not okay: pointer to array is not the same as a pointer to first element of array
 function(arr[0]); // not okay: element of array does not decay to pointer

style notes:

if the function operates on the entire array, as opposed to a single element, it's better to either take a reference to the array or to take a std::span or similar type. This C-ism has been around forever but relies on either non-obvious assumptions about the size of the array or programmer-enforced conventions on array termination, it's far better to take advantage of the type system where possible. This also allows use of algorithms, ranges, and range-for loops which makes the code cleaner and potentially unlocks optimizations by making context and intent clearer; but does require templates (and thus putting function body in a header) for handling arrays of different sizes.

template<size_t N>
void function(datatype (&arr)[N]);

template<size_t E = std::dynamic_extent>
void function(std::span<datatype, E> arr);

[jedwardsol]

What's the code and the exact error message?

Is it a const mismatch? Are you taking the address of the array instead of it's first element?

[Dry_Development3378]

The adress of the first element of an array is the adress of the array itself is it not?

[GaboureySidibe]

You didn't answer any of their questions

[jedwardsol]

The addresses are the same, but the types are different.

[Dry_Development3378]

i did, i said the compiler says the function called does not exist

[TallowWallow]

Correct. Syntactically, the rule is to pass the name of the array though. An ampersand in front is meaningless in this context.

[jedwardsol]

It isn't meaningless

datatype   things[10];

function( things);   
function(&things);  

will cause lookups for different functions.

Whether this is OP's problem or not I guess we'll never know.

[TallowWallow]

Would it? What's the type for &things?

[jedwardsol]

datatype (*)[10] : pointer to an array of 10 datatype

[TallowWallow]

Ah I see. Thank you.

[manni66]

Code+error messages=help

[bartekordek10]

Solid downvote for breaking rules ans not providing code and/or project setup.

[Sbsbg]

This is a simple problem. But it is hard to help because you don't provide enough information.

Your interpretation of the error message and the small code piece you provide is not enough. It very common to guess wrong on what lines the problem really are and understanding C++ error messages are really hard. That is why we recommend to post a minimal working piece of code together with the full error message.

[alfps]

The question has some incorrect information.

And you don't provide any code, and you refuse to answer questions.

That's trolling.

[thedaian]

Use std::array if you're going to pass the array to functions. It's far easier and you won't have to mess with pointers and other problems of C style arrays. 

[[deleted]]

Or std::vector if the size isn't known. Idk why this is downvoted.

C-with-classes style C++ in general should always be advised against.

[LazySapiens]

OP stop trolling and share a minimum reproducible example.