C Programming - Collecting data in a function outside of main() - c

Question

Write a program that asks the user to enter daily rainfall amounts. Your program will need to accept 5 daily rainfall inputs. Only allow non-negative rainfall amounts. When the user enters a negative number, tell them that the number is invalid, and that they should enter another, valid value.
Calculate the total rainfall and the average rainfall. Determine the largest daily rainfall and the smallest daily rainfall.
Output the total, average, largest, and smallest values using informative messages.
The following things cannot happen in main:
Accepting user input
Calculation of total or average
Determination of largest or smallest
Outputting results
=============================================
Right now i'm just trying to figure out how to enter the 5 numbers, I have this code so far but it's having me put it in an infinite amount of times. I've been working on this project for hours, so any advice would be amazing.
#include <stdio.h>
#include <stdlib.h>
#define SIZE 5 // have the user enter it 5 times
double CollectRainfall() {
double amount;
double rainfall[SIZE];
int i;
printf("Enter a rainfall amount: \n"); // enter amount
scanf_s("%lf", &amount);
for (i = 0; i < SIZE; i++) {
rainfall[i] = CollectRainfall();
while (amount < 0.0) { // if it's a negative number
printf("The number is invalid.\n"); // display error message if a negative # was entered
printf("Enter another rainfall amount: \n");
}
}
}
int main() {
CollectRainfall();
return 0;
}

Answer 1

As said the recursion as you have it will essentially create an infinite loop, and really, for this you dont need it either, you can do something like:
Running sample (commented changes)
#include <stdio.h>
#include <stdlib.h>
#define SIZE 5 // have the user enter it 5 times
void CollectRainfall() { //no return needed
double rainfall[SIZE], sum = 0, max = 0, min = 0;
int i;
for (i = 0; i < SIZE; i++)
{
printf("Enter a rainfall amount: \n"); // enter amount
scanf("%lf", &rainfall[i]); //save values into the array
while (rainfall[i] < 0.0)
{ // if it's a negative number
printf("The number is invalid.\n"); // display error message if a negative # was entered
printf("Enter another rainfall amount: \n");
i--; // iterate back to replace negative number
}
}
printf("Values:");
for (i = 0, min = rainfall[i]; i < SIZE; i++)
{
printf(" %.2lf", rainfall[i]); // print all values
sum += rainfall[i]; // sum values
if(rainfall[i] > max){ //max value
max = rainfall[i];
}
if(min > rainfall[i]){ //min value
min = rainfall[i];
}
}
printf("\nSum: %.2lf", sum); // print sum
printf("\nMax: %.2lf", max); // print max
printf("\nMin: %.2lf", min); // print min
printf("\nAverage: %.2lf", sum / SIZE); //print average
}
int main() {
CollectRainfall();
return 0;
}

Answer 2

You can create a struct to store you data and do the operation.
Something like:
#include <stdio.h>
#include <stdlib.h>
#define SIZE 5 // have the user enter it 5 times
typedef struct data {
double rainfall[SIZE];
double average;
double min;
double max;
} data_t;
static void collectRainfall(double rainfall[SIZE]) {
for (int i = 0; i < SIZE; i++) {
double amount;
printf("Enter a rainfall amount: \n"); // enter amount
scanf("%lf", &amount);
while (amount < 0.0) { // if it's a negative number
printf("The number is invalid.\n"); // display error message if a negative # was entered
printf("Enter a rainfall amount: \n"); // enter amount
scanf("%lf", &amount);
}
rainfall[i] = amount;
}
}
static void compute(data_t *data) {
data->min = data->rainfall[0];
data->max = data->rainfall[0];
data->average = data->rainfall[0];
for (int i = 1; i < SIZE; i++) {
double rainfall = data->rainfall[i];
if (rainfall > data->max) {
data->max = rainfall;
}
if (rainfall < data->min) {
data->min = rainfall;
}
data->average += rainfall;
}
data->average /= SIZE;
}
static void display(data_t *data) {
printf("min %f, max %f, average %f\n",
data->min, data->max, data->average);
}
int main() {
data_t data;
collectRainfall(data.rainfall);
compute(&data);
display(&data);
return 0;
}
scanf is a pain in case of bad input best is to read a line then parse it, check if strtod is ok
static void collectRainfall(double rainfall[SIZE]) {
for (int i = 0; i < SIZE; i++) {
char str[32];
double amount = -1;
printf("Enter a rainfall amount [%d/%d]: \n", i , SIZE);
while (42) {
char *res = fgets(str, sizeof(str), stdin);
if (res && (amount = strtod(str, &res)) >= 0 && res != str)
break;
printf("The number is invalid.\n");
printf("Enter a rainfall amount [%d/%d]: \n", i , SIZE);
}
rainfall[i] = amount;
}
}