How to find size of a double arr[] in c++

Question

I am new to coding and I have a double arr[]={1,2,-1.75,6};

I have tried to do

#include <iostream>
#include <math.h>
using namespace std;

void solve (double arr[]){
    int size=(sizeof(arr))/(sizeof(arr[0]));
    cout <<"size: "<<size <<endl;
    return;
}

int main(){
    double arr[]={1,2,0.75,4};
    solve(arr);
    return 0;
}

but I cannot find the size of array with type double. Any help is appreciated thanks!

In C++, when an array is pass to a function, it decays to a pointer pointing to the first element in the array, so you can't use that. I suggest using `std::vector`. Something like `solve (std::vector arr){}` and when you need the array's size, `use arr.size()` — justANewb stands with Ukraine, Jun 04 '22 at 09:13
@justANewbstandswithUkraine if he wants array semantics why not give it to him ;) https://en.cppreference.com/w/cpp/container/array — kallaballa, Jun 04 '22 at 09:22
Just avoid all this legacy trouble with plain "C" style arrays, use std::array or std::vector for arrays. They've been around since C++11 and obey all the predictable rules for passing by (const) reference. (https://en.cppreference.com/w/cpp/container/array) — Pepijn Kramer, Jun 04 '22 at 09:23
Yes, i understand that might not be possible with double arr. But for my purposes i require the size of a double arr[]. It is fine if i can push individual elements into a vector and use .size(), but the problem is how to iterate over the double arr[] without an initial size. — Kaito Ace, Jun 04 '22 at 09:24
@kallaballa Because he's trying to find a size of the array. Array's sizes has to be known at compile time, so I linked him to `std::vector` :) — justANewb stands with Ukraine, Jun 04 '22 at 09:25
@KaitoAce You can't. The size of `double arr[]` has to be known at compile time — justANewb stands with Ukraine, Jun 04 '22 at 09:27
ok let me show what i have, i just want to print size of the arr `//code below` ` #include #include using namespace std; void solve (double arr[]){ int size=(sizeof(predicted))/(sizeof(predicted[0])); cout < — Kaito Ace, Jun 04 '22 at 09:32
@KaitoAce your question has already been answered. Check the linked duplicates please. — πάντα ῥεῖ, Jun 04 '22 at 09:51
@KaitoAce also [edit] your question, if you want to add additional information, instead of burying that in comments. — πάντα ῥεῖ, Jun 04 '22 at 09:58
oh ok @justANewbstandswithUkraine, i understand now, just need to do size before passing it as reference cuz otherwise it degrades to a simple pointer. Wooo, thanks for your help! — Kaito Ace, Jun 04 '22 at 10:30
Online example of how to use arrays in C++ (not the "C" style arrays) : https://onlinegdb.com/619Y8FzlX — Pepijn Kramer, Jun 04 '22 at 12:10

How to find size of a double arr[] in c++

0 Answers0