Beginner User Input Question

I need to verify that all numerical input is positive. If not, output an error message that only positive numbers are valid and reprompt one more time. I have looked around, but am pretty confused. Maybe the while loop, but I just don't understand it well.

cout <<"The cost of a hybrid car?" << endl;
cin >> hybrid_cost;

For example, what would I do after this to meet the above paragraph?

Assuming that your variable is signed, all you have to do is loop while the input isn't positive.

The search button will take you for miles and miles :)

Quote:

---

loop until you've got a non-negative number.
read value into days
loop through each character
if this character is not a digit
break
end loop
end loop

---

http://cboard.cprogramming.com/c-pro...ve-number.html

How about this?


int hybrid_cost = 0;
do
{
cout <<"The cost of a hybrid car?" << endl;
cin >> hybrid_cost;
}
while ( ! ( 0 < hybrid_cost ) );

Quote:

---

Originally Posted by anchorblue804

How about this?

Code:

---

int hybrid_cost = 0;
do
{
  cout <<"The cost of a hybrid car?" << endl;
  cin >> hybrid_cost;
}
while ( ! ( 0 < hybrid_cost ) );

---

---

Quite good actually. If you'd add an error message or something it'd be even better. Oh, and do please put your code in code tags, it's more readable that way.

Well, while ( hybrid_cost < 0 ) ); is much more understandable than while ( ! ( 0 < hybrid_cost ) );

Quote:

---

Originally Posted by WaltP

Well, while ( hybrid_cost < 0 ) ); is much more understandable than while ( ! ( 0 < hybrid_cost ) );

---

There is a nice term for the later, guess what !?!

Quote:

---

Originally Posted by WaltP

Well, while ( hybrid_cost < 0 ) ); is much more understandable than while ( ! ( 0 < hybrid_cost ) );

---

That's possibly true but, more importantly, they mean different things.

Yes, and so does "Make a turn at the next intersection, but not a left turn"

Quote:

---

Originally Posted by WaltP

Yes, and so does "Make a turn at the next intersection, but not a left turn"

---

!(something > 0) is equivalent to (something <= 0). See, you missed the possible equality. For some, zero isn't positive. :p

Details... They always bite you in the ... :p