TigerCode TigerCode - 2 months ago 15
C++ Question

could not convert '(<expression error>)' from '<brace-enclosed initializer list>' to std::unique_ptr<int []>

I have the latest gcc compiler.
gcc (Ubuntu 6.2.0-3ubuntu11~14.04) 6.2.0

On code::blocks I've set the compiler to the GNU Compiler as default.

The error I'm getting is this
error: could not convert '{}' from '' to 'std::unique_ptr'|

The issue is in my header file at the bottom.

This was for a lab that I did in class and It worked fine last week I think - compiling the header file gives me my results but when i build from the arrayclass.cpp file it gives me this error.

Here is my implementation file ArrayClass.cpp:

#include "ArrayClass.h"

#include <memory>

using std::make_unique;

ArrayClass::ArrayClass(int capacity)
: arrSize{capacity},
arr{make_unique<int[]>(capacity)}
{
}

void ArrayClass::insert(int value)
{
if (currentSize < arrSize) {
arr[currentSize++] = value;
}
}

void ArrayClass::set(int i, int value)
{
if (i >= 0 && i < currentSize) {
arr[i] = value;
}
}

int ArrayClass::get(int i) const
{
if (i >= 0 && i < currentSize) {
return arr[i];
}
else {
return 0;
}
}

int ArrayClass::capacity() const
{
return arrSize;
}

int ArrayClass::size() const
{
return currentSize;
}


And here is my header file:

#ifndef ArrayClass_header
#define ArrayClass_header
#include <memory>

using std::unique_ptr;
using std::make_unique;

class ArrayClass
{
public:
// Constructors and Destructors

// Default constructor
// POST: Created an ArrayClass object with an array of size def_size
// Compiler default suffices (see variable initializations at end of header)
ArrayClass() = default;

// Constructor
// PRE: capacity > 0
// POST: Created an ArrayClass object with an array of size capacity
// PARAM: capacity = size of the array to allocate
ArrayClass(int capacity);

// Destructor
// POST: All dynamic memory associated with object de-allocated
// ~ArrayClass();

// Set the value of the next free element
// PRE: currentSize < arraySize
// POST: Element at index currentSize set to value
// PARAM: value = value to be set
void insert(int value);

// Return an element's value
// PRE: 0 <= i < arraySize
// POST: Returned the value at index i
// PARAM: i = index of value to be returned
int get(int i) const;

// Set an element's value
// PRE: 0 <= i < arraySize
// POST: Element at index i set to value
// PARAM: i = index of element to be changed
// value = value to be set
void set(int i, int value);

// POST: Return the currently allocated space
int capacity() const;

// POST: Return the number of elements
int size() const;

// The default capacity
static constexpr int def_capacity {10};

private:
int arrSize {def_capacity};
int currentSize {0};
unique_ptr<int[]> arr {make_unique<int[]>(capacity)};
};

#endif

Answer

I'm pretty sure the error is here:

unique_ptr<int[]> arr {make_unique<int[]>(capacity)};

capacity should be def_capacity instead, since as of now, you're using the name of a function but without the round parentheses, which makes the compiler stumble while parsing the {} initializer list.

Edit: Yes, it compiles fine with the fix. There are two errors, the first one being "invalid use of non-static member function int ArrayClass::capacity() const". Then the initializer-list one follows, since the compiler can't parse the initalizer list.

Edit 2: In the .cpp file, in the constructor definition, capacity appears to shadow the ArrayClass::capacity() function, but I still think it'd be better to avoid such a collision just for clarity sake.

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