Positive, negative, neutral, invalid integer program

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Good day! Our professor assigned me to do an activity in C that I will present in front of class, but I'm having trouble. I am supposed to create a program that takes user input that identifies if the input is positive, negative, or neutral. If the user inputs a character or a string, it is supposed to output "Invalid Input.". However, I can not seem to make the last condition work. Any tips? I just started so any help will be appreciated. Thank you so much!

What I have tried:

C++

#include <stdio.h>
int main()
{
	int num;
	printf("Input a number: ");
	scanf("%i", &num);
	
	if (num>0.0) {
		printf("Positive");
	}	
	else if (num<0.0) {
		printf("Negative");
	}	
	else if (num==0.0) {
		printf("Neutral");
	}	
	else {
		printf("Invalid Input");
	}
	
	return 0; 
}

I also tried changing the elif statements to if statements but it always included Invalid Input in every output.

Posted 4-Oct-20 0:48am

Lamborkiki

Updated 4-Oct-20 7:11am

KarstenK

v2

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Rick York 4-Oct-20 12:45pm

First, define what valid input is. Anything else would be invalid input. You should be able to determine what the type of input is you receive.

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Richard MacCutchan · Accepted Answer · 2020-10-04T00:57:00

The first issue is that you are reading an integer value and then comparing it to a floating point. So use the simple integral value 0 for your comparison. The second issue is that if you enter a string rather than a number, then scanf will not return anything so num will contain whatever was there before. You need to capture the return value from scanf to check if you read a valid number. Something like:

C++

printf("Input a number: ");
int count = scanf("%i", &num);
if (count != 1)
{
    printf("Invalid Input");
}
else // ... now you can check the value of num