/*
    functions.c
	Jeff Ondich, 26 April 2019
    Part of a quick intro to C

    You'll have questions. Such as:
   
        what the heck does "const char *" mean?

    Write them down, discuss them, ask them!
*/
#include <stdio.h>

// These are called "prototypes" in C and C++. They're a way of
// saying "there's going to be a function with this particular
// interface, so you can go ahead and call these functions, but
// they'll need to be implemented somewhere".
int fibonacci(int n);
int occurrences(char character, const char *string);

int main() {
    // Let's print out some Fibonacci numbers.
    for (int k = 0; k < 15; k++) {
        printf("%d ", fibonacci(k));
    }
    printf("\n\n");

    // And here's a function that has a string paramater.
    char word[] = "Mississippi";
    char character = 'i';
    int occurrenceCount = occurrences(character, word);
    printf("There are %d occurrences of the character '%c' in the word \"%s\"\n", occurrenceCount, character, word);

    return 0;
}

// Returns the nth Fibonacci number. Assumes that the Fibonacci
// numbers start at index 0, so fib0 = 1, fib1 = 1, fib2 = 2, etc.
int fibonacci(int n) {
    int previous = 1;
    int current = 1;
    for (int k = 1; k <= n; k++) {
        int new = current + previous;
        previous = current;
        current = new;
    }
    return current;
}

// Returns the number of times character occurs in string.
int occurrences(char character, const char *string) {
    int n = 0;
    for (int k = 0; string[k] != '\0'; k++) {
        if (string[k] == character) {
            n++;
        }
    }
    return n;
}