/*
	COMP2401/2001 - W13

	


	mjh - 2013
*/


#include <stdio.h>


// function that takes memory addresses as input

int add1int(int* x){
	// x is a local variable to the function.
	// its value is the memory location of the argument
	// passed to it.  It is a memory location (pointer)


	// let's grab the value that x points to
	int local_int = *x;

	return local_int + 1;

	// could have, more compactly, had
	// return *x + 1; or
 	// return (*x) + 1;

	// Note: this is very different from
	// return *(x + 1)

}


// this function lools like it takes an array as input.
// but, remember that an array is just a pointer!
// so, the input is really a pointer to a char.  thus, 
// whenever we pass an array into a function, we never 
// make a copy of the array, we just pass the location of 
// the array.

int* add1(int x[], int n){
	for(int i=0; i<n; i+=1){
		x[i] = x[i] + 1;
	}
	return x;
}


// Note: we could have written the function as

int* add1_alt(int* pointer_to_array, int array_length){
	for(int i=0; i<array_length; i+=1){
		*(pointer_to_array+i) += 1;
	}
	return pointer_to_array;
}

// why did we need to return the pointer?  the changes are all made
// and will persists after the function is ended.  This functions 
// might also be re-written as

void add1_alt2(int* array_ptr, int array_size){
	for(int i=0; i<array_size; i+=1){
		array_ptr[i] += 1;
	}
}



// function that diplayes memory location and value
// of input pointer
void print(int* array_ptr){
	// array_ptr is local copy of input argument
	printf("memory location for local input = %p\n", &array_ptr);
	printf("value of local input = %p\n", array_ptr);
}


int main(){
	int xx[] = {1, 2, 3, -10};
	int* xp = xx;

	int nn = 4;
	for(int i=0; i<nn; i+=1){printf("%d ", xp[i]);	}
	printf("\n");

	xp = add1(xp,nn);
	for(int i=0; i<nn; i+=1){printf("%d ", xp[i]);	}
	printf("\n");

	add1_alt(xp,nn);
	for(int i=0; i<nn; i+=1){printf("%d ", xp[i]);	}
	printf("\n");

	add1_alt2(xp,nn);
	for(int i=0; i<nn; i+=1){printf("%d ", xp[i]);	}
	printf("\n");


	printf("\n\n------------------------\nMake sure you understand why some of these values are the same and some are different!\n");
	printf("memory location for xp=%p\n", &xp);
	printf("value of x=%p\n", xp);

	print(xp);


}