/*
* Program 1 - Find the coding style violations in this program.
* Joe Student
* CPE 101-xx
* Adds, subtracts, multiplies and divides common fractions, displaying
* results in reduced form.
*/
#include <stdio.h>
#include <stdlib.h> /* provides function abs */
/* Function prototypes */
void scan_fraction(int *nump, int *denomp);
char get_operator(void);
void add_fractions(int numer1, int denom1, int numer2, int denom2,
int *n_ansp, int *d_ansp);
void multiply_fractions(int numer1, int denom1, int numer2, int denom2,
int *n_ansp, int *d_ansp);
int find_gcd (int numer1, int numer2);
void reduce_fraction(int *nump, int *denomp);
void print_fraction(int num, int denom);
/* Main Function */
int
main(void)
{
int numer1; /* numerator of first fraction */
int denom1; /* denominator of first fraction */
int numer2; /* numerator of second fraction */
int denom2; /* denominator of second fraction */
char operator; /* arithmetic operator + - * or / */
char again; /* y or n depending on user's desire to continue */
int n_ans; /* numerator of answer */
int d_ans; /* denominator of answer */
/* While the user wants to continue, gets and solves arithmetic
problems with common fractions */
do
{
/* Gets the numerator and denominator of two fractions to manipulate */
scan_fraction(&numer1, &denom1);
/* Get the desired arithmetic operator */
operator = get_operator();
scan_fraction(&numer2, &denom2);
/* Perform the needed operation for this operator */
switch (operator)
{
case '+':
add_fractions(numer1, denom1, numer2, denom2, &n_ans, &d_ans);
break;
case '-':
add_fractions(numer1, denom1, -numer2, denom2, &n_ans, &d_ans);
break;
case '*':
multiply_fractions(numer1, denom1, numer2, denom2, &n_ans, &d_ans);
break;
case '/':
multiply_fractions(numer1, denom1, denom2, numer2, &n_ans, &d_ans);
break;
}
/* Reduce the answer to simplest terms */
reduce_fraction(&n_ans, &d_ans);
/* Displays problem and result */
printf("\n");
print_fraction(numer1, denom1);
printf(" %c ", operator);
print_fraction(numer2, denom2);
printf(" = ");
print_fraction(n_ans, d_ans);
/* Asks user about doing another problem */
printf("\nDo another problem? (y/n)> ");
scanf(" %c", &again);
} while (again == 'y' || again == 'Y');
return (0);
}
/*
* (INCOMPLETE) Gets and returns a valid fraction as its result
* A valid fraction is of this form: integer/positive integer
* Pre : none
*/
void
scan_fraction(int *nump, int *denomp)
{
char slash; /* character between numerator and denominator */
int status; /* status code returned by scanf indicating number of valid values obtained */
int error; /* flag indicating presence of an error */
char discard; /* unprocessed character from input line */
do {
/* No errors detected yet */
error = 0;
/* Get a fraction from the user */
printf("Enter a common fraction as two integers separated ");
printf("by a slash> ");
status = scanf("%d %c%d",_______, _______, _______);
/* Validate the fraction */
if (status < 3) {
error = 1;
printf("Invalid-please read directions carefully\n");
} else if (slash != '/') {
error = 1;
printf("Invalid-separate numerator and denominator");
printf(" by a slash (/)\n");
} else if (*denomp <= 0) {
error = 1;
printf("Invalid-denominator must be positive\n");
}
/* Discard extra input characters */
do {
scanf("%c", &discard);
} while (discard != '\n');
} while (error);
}
/*
* Gets and returns a valid arithmetic operator. Skips over newline
* characters and permits re-entry of operator in case of error.
*/
char
get_operator(void)
{
char operator;
printf("Enter an arithmetic operator (+,-,*, or /)\n> ");
for (scanf("%c", &operator);
operator != '+' && operator != '-' &&
operator != '*' && operator != '/';
scanf("%c", &operator)) {
if (operator != '\n')
printf("%c invalid, reenter operator (+,-, *,/)\n> ", operator);
}
return (operator);
}
/*
* Adds fractions represented by pairs of integers.
* Pre: numer1, denom1, numer2, denom2 are defined;
* n_ansp and d_ansp are addresses of type int variables.
* Post: sum of numer1/denom1 and numer2/denom2 is stored in variables pointed
* to by n_ansp and d_ansp. Result is not reduced.
*/
void
add_fractions(int numer1, int denom1, /* input - first fraction */
int numer2, int denom2, /* input - second fraction */
int *n_ansp, int *d_ansp) /* output - sum of 2 fractions*/
{
int denom, /* common denominator used for sum (may not be least) */
numer, /* numerator of sum */
sign_factor; /* -1 for a negative, 1 otherwise */
/* Finds a common denominator */
denom = denom1 * denom2;
/* Computes numerator */
numer = numer1 * denom2 + numer2 * denom1;
/* Adjusts sign (at most, numerator should be negative) */
if (numer * denom >= 0)
sign_factor = 1;
else
sign_factor = -1;
numer = sign_factor * abs(numer);
denom = abs(denom);
/* Returns result */
*n_ansp = numer;
*d_ansp = denom;
}
/*
***** STUB *****
* Multiplies fractions represented by pairs of integers.
* Pre: numer1, denom1, numer2, denom2 are defined;
* n_ansp and d_ansp are addresses of type int variables.
* Post: product of numer1/denom1 and numer2/denom2 is stored in variables pointed
* to by n_ansp and d_ansp. Result is not reduced.
*/
void
multiply_fractions(int numer1, int denom1, /* input - first fraction */
int numer2, int denom2, /* input - second fraction */
int *n_ansp, /* output - */
int *d_ansp) /* product of 2 fractions */
{
/* Displays trace message */
printf("\nEntering multiply_fractions with\n");
printf("numer1 = %d, denom1 = %d, numer2 = %d, denom2 = %d\n", numer1, denom1, numer2, denom2);
/* Defines output arguments */
*n_ansp = 1;
*d_ansp = 1;
}
/*
***** STUB *****
* Finds greatest common divisor of two integers
*/
int
find_gcd (int numer1, int numer2) /* input - two integers */
{
int gcd;
/* Displays trace message */
printf("\nEntering find_gcd with numer1 = %d, numer2 = %d\n", numer1, numer2);
/* Asks user for gcd */
printf("gcd of %d and %d?> ", numer1, numer2);
scanf("%d", &gcd);
/* Displays exit trace message */
printf("find_gcd returning %d\n", gcd);
return (gcd);
}
/*
* Reduces a fraction by dividing its numerator and denominator by their
* greatest common divisor.
*/
void
reduce_fraction(int *nump, /* input/output - */
int *denomp) /* numerator and denominator of fraction */
{
int gcd; /* greatest common divisor of numerator & denominator */
gcd = find_gcd(*nump, *denomp);
*nump = *nump / gcd;
*denomp = *denomp / gcd;
}
/*
* Displays pair of integers as a fraction.
*/
void
print_fraction(int num, int denom) /* input - numerator & denominator */
{
printf("%d/%d", num, denom);
}