creating simple calculator using recursive function in C programming

i am trying to make a simple calculator that has 3 functions

s_exp(float sub_exp,char op): this function receives sub_exp(floating number) and op(an operator) and calculates

Num op(+ or - ) recursive(num)

Here is what i did but i am keep getting errors

#include <stdio.h>
#include <string.h>

//Input: 'sub_exp' the value of the sub expression to the left of'op'
//op: an operator: + or -
//Effect: the whole expression is evaluated using recursion
//output: this ufnctino returns the value of the expression
float s_exp(float sub_exp, char op)
{

    switch (op)
    {
    case '+':
    return sub_exp + s_exp(sub_exp, op) ;   //add the function recursively
    break;
    case '-':
    return sub_exp- s_exp(sub_exp,op); //subtract the function recursively
    break;

    }


}

float get_num() //this function receives number
{
    static float num;
    printf("please input the numerical value \n");
    scanf_s("%f", &num);
    printf("%5.5f", num);

    return num;
}
char get_op() //this function receives an operator
{
    static char oper;
    //receives the variables and returns the variable 
    printf("please input the operator");
    scanf_s("%c",&oper);
    printf("\n %c", oper);

    return oper;

}

void main(void){
    //run the recursive function
    s_exp(get_num(), get_op());



}