C++ Stack by Array Implementation

Question

What I want to happen is for the pushFront(int) function to do this:

bool stack::pushFront( const int n )
{
  items[++top] = n;  // where top is the top of the stack
  return true; // only return true when the push is successful
}

items is a struct type of the object "item". Have a look:

class stack
{
  stack(int capacity);
  ~stack(void);
  ...
  private:
    int maxSize; // is for the item stack
    int top;     // is the top of the stack
    struct item {
    int n;
    };
    item        *items;

i've defined the ctor to the stack class object and dtor as follows:

stack::stack(int capacity)
{   
    items = new item[capacity];

    if ( items == NULL ) {
      throw "Cannot Allocoate Sufficient Memmory";
      exit(1); 
    }
    maxSize = capacity;
    top     = -1;
}

stack::~stack(void)
{
    delete [] items;

    items    = NULL;
    maxSize  = 0;
    top      = -1;
}

Yes the main issue for me is the items[++top] = n; statement. I've been trying to find ways around it like below:

bool stack::pushFront(const int n)
{
    int *a = new int[maxSize];
    a[++top] = n;

    return true;
}

But I cant drag (+) 'a' array out to see those actual array elements... Which is what I was hoping to happen..

What I want is for the statement items[++top] = n; to work..

Geerad · Accepted Answer · 2009-09-07 07:15:45Z

2

You can't assign an int value to an item, because you haven't told the compiler how to do that.

You need to either write a constructor or operator= for item that takes an int as a parameter or use

items[++top].n = n;

answered Sep 7, 2009 at 7:15

Geerad

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Comments

Gilles 'SO- stop being evil' · Accepted Answer · 2011-07-26 11:50:42Z

0

bool stack::pushFront( const int n ) 
{
    if(top == maxSize-1)
        return false;
    items[++top].n = n;  // where top is the top of the stack
    return true; // only return true when the push is successful
}

edited Jul 26, 2011 at 11:50

Gilles 'SO- stop being evil'

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answered Sep 9, 2009 at 11:30

GG.

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Comments

Timothy Pratley · Accepted Answer · 2009-09-07 08:25:29Z

0

It appears you have defined a stack of fixed size. You should check that adding to the stack does not exceed the size. To pushFront, you just need to copy the data in the array to make space for the 0th element to be modified:


bool stack::push(const int n)
{
    if ( top >= capacity-1 ) return false;
    items[++top].n = n
}

bool stack::pushFront(const int n)
{
    if ( top >= capacity-1 ) return false;
    bcopy( items, items+1, top+1 );
    items[0].n = n;
    return true;
}

edited Sep 7, 2009 at 8:25

answered Sep 7, 2009 at 4:01

Timothy Pratley

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3 Comments

user40120 Over a year ago

actually, the statement items[++top] = n; within the body of the bool stack::pushFront( const int n) function, is invalid and i recieve this error: error C2679: binary '=' : no operator found which takes a right-hand operand of type 'const int' (or there is no acceptable conversion). Followed by: could be 'stack::item &stack::item::operator =(const stack::item &)' How can I get away with writing the code as items[++top] = n; ?

user40120 Over a year ago

everywhere I use items as an array assigned to n, i get an error :/

Timothy Pratley Over a year ago

As Geerad pointed out it should be: items[++top].n = n; because items is a structure.

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