confused on problem

[renniegq]

I have to write a simple calculator that inputs an expression with two values separated by an operator computer will print out results. Calculator should include the ^ operator for exponentiation. All calculations should be done in an appropriate function (the functions will be small) and results printed in main().

functions and Variables:

main()
op -- Operator
x, y -- Values for Calculations
add()
subtract()
multiply()
divide()
exponentiate()
a, b --Local variables for each function

Output:
Enter expression (q to quit): 34.7 + 23.5
58.2
Enter expression (q to quit): 5.27 * 32.6
171.802
Enter expression (q to quit): 1.41414 ^ 2
1.99979
Enter expression (q to quit): 657.80 / 0
Can't divide by 0
Enter expression (q to quit): 534 & 26
Invalid operator
Enter expression (q to quit): q


I am having trouble with the concept of functions and how to set this problem up. Please help. Below is what I have started.

#include <stdio.h>

/*void add()
void subtract()
void multiply()
void divide()
void exponentiate()*/


void main(void)

{	char op;
	float x, y;
	
	printf("Enter expression (q to quit): ");
	scanf("%f %c %f", &x, &op, &y);

	while(
		



}

[ronin]

First thing is if you're going to read in an equation, then try an array of chars to avoid the pitfalls of user's inputting wrong data types, scan that array to get the values and the operation

printf("Enter the operation: ");
fgets(char_arr, sizeof(char_arr), stdin);

You know a few things... the first is you expect a number, then an operation, and another number. You can use functions like strchr to split the array as you require, or sscanf to parse the array according to the values that you expect.

functions are fairly easy.

int getProd(int, int); /*prototype */

.....
main

printf("enter a number: ");
scanf("%d", &num1);

printf("enter another number: ");
scanf("%d", &num2);

printf("%d * %d = %d", num1, num2, getProd(num1, num2));


end main
....

int getProd(int a, int b) /* definition */
{
    return (a * b);
}

[renniegq]

I really don't understand this problem and the answer I received could somene else please help me. I'm just suppose to use the functions, variable that I stated. Could someone please help.

[Thantos]

If you are intent on using scanf() so be it, but beware of the possible problems.

This should help:

switch (op)
  {
  case '*':  result=multiply(x,y);break;
  case '/':  result=divide(x,y);break;
  case '+':  result=add(x,y);break;
  case '-':  result=subtract(x,y);break;
  case '^': result=exponentiate(x,y);break
  default:  printf("No valid operator.");
  }

The function themselves should be a piece of cake as they are just doing basic math functions;

[renniegq]

thanks, I'll give it a shot.