Pointer and If Statement

Hello,

I am trying to use an if statement which has a pointer in it to determine which function to use.

The original code would be -

Code:

---

pqueue *pq = new_bounded_pqueue(5,le_artist);

---

I want to use an if statement so if a user inputs a certain variable it will declare a different line of code. Here is what I have done so far -

Code:

---

printf("Please enter if you want to order by ascending or descending, A = Assending, D = Descending:  \n");    scanf("%c", &order);
   
    pqueue *pq;


    if (order == 'A' || order == 'a')    {
    pqueue *pq = new_bounded_pqueue(5,le_artist);
    }
    else if (order == 'D' || order == 'd')
    {
    pqueue *pq = new_bounded_pqueue(5,le_artistdec);
    }

---

Once compiled the program runs but as soon as I input data I return a segmentation fault.

It's a matter of variable scope. You're creating new variables don't exist outside of their individual blocks. Instead just assign to the pq variable.

Code:

---

pq = new_bounded_queue(4, le_artist);

---

etc.

Quote:

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Originally Posted by rags_to_riches

It's a matter of variable scope. You're creating new variables don't exist outside of their individual blocks. Instead just assign to the pq variable.

Code:

---

pq = new_bounded_queue(4, le_artist);

---

etc.

---

I was silly and realised that after, if you check my original post i've updated it and now I have a segmentation fault.

Thanks :)

Within the body of the if statement, you declared a variable named pq. You want to assign to the variable named pq that was declared before the if statement.

I believe that you are making duplicate declarations of your variable pointer in the begining and then again when assigning it to the new_bounded_pqueue() function.

I believe you should remove the declaration and you just use the name of the pointer variable and you'll be just fine.

Quote:

---

Originally Posted by C-Lover

I believe that you are making duplicate declarations of your variable pointer in the begining and then again when assigning it to the new_bounded_pqueue() function.

I believe you should remove the declaration and you just use the name of the pointer variable and you'll be just fine.

---

I figured that would be the reason last night it's just the syntax I can't get correct, could you possibly push me in the right direction so I can learn from it?

Err... this is actually the same problem that rags_to_riches pointed out in post #2. Your edit did not fix the problem. Rather:

Code:

---

printf("Please enter if you want to order by ascending or descending, A = Assending, D = Descending:  \n");
scanf("%c", &order);

pqueue *pq;
if (order == 'A' || order == 'a')
{
    pq = new_bounded_pqueue(5, le_artist);
}
else if (order == 'D' || order == 'd')
{
    pq = new_bounded_pqueue(5, le_artistdec);
}

---

Quote:

---

Originally Posted by laserlight

Err... this is actually the same problem that rags_to_riches pointed out in post #2. Your edit did not fix the problem. Rather:

Code:

---

printf("Please enter if you want to order by ascending or descending, A = Assending, D = Descending:  \n");
scanf("%c", &order);

pqueue *pq;
if (order == 'A' || order == 'a')
{
    pq = new_bounded_pqueue(5, le_artist);
}
else if (order == 'D' || order == 'd')
{
    pq = new_bounded_pqueue(5, le_artistdec);
}

---

---

Thank you! I think the issue that was confusing me was the way I laid out my code. I'm used to seeing declaring pointers like this

Code:

---

pqueue * pq;

---

With the space, it's still early days I guess ;)

Appreciate the help!

You're welcome :)

You could read Stroustrup's answer to the FAQ: Is ``int* p;'' right or is ``int *p;'' right?