#ifndef _NUM_H
#define _NUM_H

#include <stdio.h>

/*
 * High-precision arithmetic on non-negative number in base 10.
 */

typedef struct num Num;

/* constructs a Num from a string */
/* string contains representation of the number
 * in base 10, e.g. numCreate("314159");
 * Returns a null pointer (0) if the string contains any non-digits.
 * Leading zeros are OK: numCreate("012") parses as 12.
 * Empty string parses as 0 */
Num * numCreate(const char *s);

/* Free all resources used by a Num */
void numDestroy(Num *n);

/* Get the value of the i-th least significant digit of a Num.
 * Returns 0 if i is out of range.
 * Example:
 *   n = numCreate("12345");
 *   numGetDigit(n, 0) == 5
 *   numGetDigit(n, 3) == 2
 *   numGetDigit(n, 17) == 0
 *   numGetDigit(n, -12) == 0
 */
int numGetDigit(const Num *n, int i);

/* add two Nums, returning a new Num */
/* does not destroy its inputs, caller must destroy output */
Num * numAdd(const Num *x, const Num *y);

/* multiply two Nums, returning a new Num */
/* does not destroy its inputs, caller must destroy output */
Num * numMultiply(const Num *x, const Num *y);

/* Print the digits of a number to file.
 * Do not print any leading zeros unless n is zero. */
void numPrint(const Num *n, FILE *f);

#endif /* _NUM_H */