Don't know what I'm doing wrong in switch/case statement

[Caith]

I broke up the parts to see what was wrong, but I couldn't figure it out.
I think the main issue is with case 1, because case 2 and 3 work fine without it. But then if I take out case 2 and 3, such that 1 is the only one left, it works perfectly fine.

I am confused!

#include <iostream>
using namespace std;
int power (int a,int b) {
	int c=a;
	while (1 < b) {
		a*=c;
		b--;
	}
	return a;
}
void swap (int a, int b) {
	int swap=a;
	a=b;
	b=swap;
	return;
}
int sum (int* a, int b) {
	int total=0;
	for (int i=0; b>i; i++) {total+=*(a+i);}
	return total;
}

int main () {
	cout << "Do you want to find the total (hit number 1), find the power (hit number 2) or switch numbers (hit number 3)?";
	int v,r;
	cin >> v;
	switch (v) {
		case 1:
		cout << "How many numbers do you want to add?";
		cin >> r;
		int* a=new int [r];
		for (int i=0; r>i; i++) {cout << "Enter number: ";
		cin >> *(a+i);}
		cout << sum(a,r);
		delete a;
		break;

	case 2:
		char choice;
		while (choice='y') {
			cout << "Enter 2 numbers: ";
			int x,y;
			cin >> x >> y;
			cout << x << " to the power of " << y << " is " << power(x,y) <<endl;
			cout << "Do you want to compute again? Hit y if yes, enter anything else for no" << endl;
			cin >> choice; }
			break;
				

	case 3:
		cout << "Enter two numbers: ";
		int first, second;
		cin >> first >> second;
		swap (first,second);
		cout << "It is done.";
		break;
	default: 
		cout << "I didn't get that, please re-enter 1, 2 or 3";
		cin >> v;

	}



	system ("pause");
}

[28poGNh0]

You should use the explicit block {}

case 1:
        {
            cout << "How many numbers do you want to add?";
            cin >> r;
            int* a=new int [r];
            for (int i=0; r>i; i++) {cout << "Enter number: ";
            cin >> *(a+i);}
            cout << sum(a,r);
            delete a;
        }

also your while is not gonna compare ,but assigning 'y' to choice what out while (choice='y') must turn to while (choice=='y')

[nvrmnd]

you should use braces {} when declaring something inside a case

[TheBeardedQuack]

Strictly speaking the cases can be used without the curly braces however it is not recommended because if any variables are declared in the case then that variable remains for the rest of the switch statement, so if you're not careful this can cause problems...
Some compilers may complain at this whereas others may let it slip right through.

[28poGNh0]

this can cause problems

like what?

[TheIdeasMan]

@Caith

Does your swap function work? It's a void function with the arguments assigned to local variables, so it won't change the value of any variable in the main() program. The args really need to be pointers or references in this case.

There is no output to show that the numbers have been swapped.

Your for loops seem to be the reverse of the normal convention.

for (int i=0; b>i; i++)

Try this form instead:

for (int i=0; i < b; i++)

Rather than use pointer arithmetic for your dynamic array, use the [] operator - it's easier & clearer.

The power function could be written more clearly IMO.

Hopefully these points are useful and help you out a bit.

[Mats]

Your power statement also needs a case for n ^ 0 (which is always equal to 1).

[TheBeardedQuack]

[quote]like what?[/code]
You know, the usual stuff...
Why don't you write the same declaration twice and see what the outcome is?

int a = 0;
int a = 1;    //Error: variable already defined (or something like that) 

Is what happens in this:

int test = //Whatever random value
switch(test){
case 1:
    char ret[] = "one";
    std::cout << ret;
case 2:
    char ret[] = "two";
    std::cout << ret;
default:
    char ret[] = "dunno";
    std::cout << ret;
}

This is quite obviously going to cause a problem because I've not included a break and if the value is 1 for example the program sees this

char ret[] = "one";
std::cout << ret;
char ret[] = "dunno";    //Error
std::cout << ret;

EDIT: In most cases a break is used once just one solution is found so more often then not there isn't a problem because break will tell switch to stop looking for any further matches, otherwise chances are that you'll get caught in the default catch.
However it's always considered "good practice" to wrap the cases up in there own scope blocks