Return a new array with specified values?

Question

Is there a way to write the following function code

int* returnFilledArray() {
 int* arr = new int[2];
 arr[0] = 1;
 arr[1] = 2;
 return arr;
}

somehow like that? (create and fill the array as one liner).

int* returnFilledArray() {
 return new int {1,2};
}

if have tried various combinations, but I allways get some syntax errors, so when if it's possible I would be thankful for a detailed explanation.

Be aware that if you create and return an array like that, there is no way to know how long it actually is, unless you have a known constant length for all arrays. I'd much rather recommend std::vector instead of a plain array. — Mephane
– Mephane, Commented Apr 13, 2011 at 13:17
@Mephane: std::vector also has the advantage that you could use Boost.Assign (only needed pre-C++11). — Björn Pollex
– Björn Pollex, Commented Apr 13, 2011 at 13:26
@moon: int[] returnFilledArray(); and int* returnFilledArray() are exactly the same function signature, so that comment (while upvoted) makes no sense at all. — David Rodríguez - dribeas
– David Rodríguez - dribeas, Commented Apr 13, 2011 at 13:26
I can't use std::vector because we have to code a small compiler without using datastructures from the std. — Nicola Coretti
– Nicola Coretti, Commented Apr 13, 2011 at 13:32

Nim · Accepted Answer · 2011-04-13 13:25:07Z

3

Yes..

std::vector<int> returnFilledArray()
{
  int a[] = {1, 2};
  return std::vector<int>(a, a+2);
}

answered Apr 13, 2011 at 13:25

Nim

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John Dibling · Accepted Answer · 2011-04-13 15:33:44Z

1

You cannot do what you are trying to do in Standard C++ (03) without using special libraries.

answered Apr 13, 2011 at 15:33

John Dibling

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Comments

Jeff Foster · Accepted Answer · 2011-04-13 13:12:58Z

1

C++ 0x supports initializer lists - is that an option for you?

answered Apr 13, 2011 at 13:12

Jeff Foster

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1 Comment

Nicola Coretti Over a year ago

I just wanted to know if it is possible because you can do something like that in Java. I do not need it necessarily.

Community · Accepted Answer · 2017-05-23 11:43:54Z

1

I had answered similar question here. You can use following technique:

template<typename T, T _0, T _1, T _2, T _3, T _4> struct Array
{
  static T* Init (T *a)
  {
    a[0] = _0;
    a[1] = _1;
    a[2] = _2;
    a[3] = _3;
    a[4] = _4;
    return a;
  }
};

int* fun ()
{
  return Array<int, 1, 2, 3, 4, 5>::Init(new int[5]);
}

edited May 23, 2017 at 11:43

CommunityBot

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answered Apr 13, 2011 at 13:29

iammilind

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3 Comments

iammilind Over a year ago

this is just an example for 5 elements; you can change the number of elements as per your need. Here the example is for int, but the same struct you can use for any type.

Nicola Coretti Over a year ago

So a simple version like in java: public static int[] myFunc() { return new int[] {2,3,4,19}; } is in c++ not possible?

iammilind Over a year ago

Not in current standarad, in C++0x the same feature as Java is introduced called "Initializer lists" where you can declare such arrays. Additionally, you can initialize variables when you declare them in `class' itself.

TonyK · Accepted Answer · 2011-04-13 13:34:54Z

0

In C++0x:

#include <vector>
std::vector<int> returnFilledArray()
{
  return std::vector<int> {1,2} ;
}

answered Apr 13, 2011 at 13:34

TonyK

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1 Comment

John Dibling Over a year ago

He said he can't use a vector

John Dibling · Accepted Answer · 2011-04-13 16:55:09Z

0

If you're not allowed to use std::vector, then you can try a macro:

#define FILLED_ARRAY(name) int name[] = {1, 2}

edited Apr 13, 2011 at 16:55

John Dibling

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answered Apr 13, 2011 at 13:37

Donotalo

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5 Comments

John Dibling Over a year ago

-1: he wants a dynamically allocated array. this one is automatic, and will fall off the stack.

Donotalo Over a year ago

i wasn't sure if he REALLY wants the array to be on heap. or just wants a one liner.

John Dibling Over a year ago

Well, I guess I'm not sure either, so I edited your post and reversed the d/v

Donotalo Over a year ago

@John, thank you. but what is the edit!? i don't see any change.

John Dibling Over a year ago

All I did was add a space at the end. I couldn't reverse my d/v because it had been there for 15 minutes. So I just edited it myself with an empty edit. :)

Muhammad Umar Farooq · Accepted Answer · 2015-08-28 07:49:17Z

0

I was able to do similar task using

int *ptr = new int[]{1, 2, 3};

you can then return from your function as

return (new int[]{1, 2, 3});

answered Aug 28, 2015 at 7:49

Muhammad Umar Farooq

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