Balanced ternary: Difference between revisions

=={{header|C}}==

{{trans|Perl}}

<lang c>#include <stdio.h>

#include <string.h>

void reverse(char *p) {

size_t len = strlen(p);

char *r = p + len - 1;

while (p < r) {

*p ^= *r;

*r ^= *p;

*p++ ^= *r--;

}

}

void to_bt(int n, char *b) {

static char d[] = { '0', '+', '-' };

static int v[] = { 0, 1, -1 };

char *ptr = b;

*ptr = 0;

while (n) {

int r = n % 3;

if (r < 0) {

r += 3;

}

*ptr = d[r];

*(++ptr) = 0;

n -= v[r];

n /= 3;

}

reverse(b);

}

int from_bt(const char *a) {

int n = 0;

while (*a != '\0') {

n *= 3;

if (*a == '+') {

n++;

} else if (*a == '-') {

n--;

}

a++;

}

return n;

}

char last_char(char *ptr) {

char c;

if (ptr == NULL || *ptr == '\0') {

return '\0';

}

while (*ptr != '\0') {

ptr++;

}

ptr--;

c = *ptr;

*ptr = 0;

return c;

}

void add(const char *b1, const char *b2, char *out) {

if (*b1 != '\0' && *b2 != '\0') {

char c1[16];

char c2[16];

char ob1[16];

char ob2[16];

char d[3] = { 0, 0, 0 };

char L1, L2;

strcpy(c1, b1);

strcpy(c2, b2);

L1 = last_char(c1);

L2 = last_char(c2);

if (L2 < L1) {

L2 ^= L1;

L1 ^= L2;

L2 ^= L1;

}

if (L1 == '-') {

if (L2 == '0') {

d[0] = '-';

}

if (L2 == '-') {

d[0] = '+';

d[1] = '-';

}

}

if (L1 == '+') {

if (L2 == '0') {

d[0] = '+';

}

if (L2 == '-') {

d[0] = '0';

}

if (L2 == '+') {

d[0] = '-';

d[1] = '+';

}

}

if (L1 == '0') {

if (L2 == '0') {

d[0] = '0';

}

}

add(c1, &d[1], ob1);

add(ob1, c2, ob2);

strcpy(out, ob2);

d[1] = 0;

strcat(out, d);

} else if (*b1 != '\0') {

strcpy(out, b1);

} else if (*b2 != '\0') {

strcpy(out, b2);

} else {

*out = '\0';

}

}

void unary_minus(const char *b, char *out) {

while (*b != '\0') {

if (*b == '-') {

*out++ = '+';

b++;

} else if (*b == '+') {

*out++ = '-';

b++;

} else {

*out++ = *b++;

}

}

*out = '\0';

}

void subtract(const char *b1, const char *b2, char *out) {

char buf[16];

unary_minus(b2, buf);

add(b1, buf, out);

}

void mult(const char *b1, const char *b2, char *out) {

char r[16] = "0";

char t[16];

char c1[16];

char c2[16];

char *ptr = c2;

strcpy(c1, b1);

strcpy(c2, b2);

reverse(c2);

while (*ptr != '\0') {

if (*ptr == '+') {

add(r, c1, t);

strcpy(r, t);

}

if (*ptr == '-') {

subtract(r, c1, t);

strcpy(r, t);

}

strcat(c1, "0");

ptr++;

}

ptr = r;

while (*ptr == '0') {

ptr++;

}

strcpy(out, ptr);

}

int main() {

const char *a = "+-0++0+";

char b[16];

const char *c = "+-++-";

char t[16];

char d[16];

to_bt(-436, b);

subtract(b, c, t);

mult(a, t, d);

printf(" a: %14s %10d\n", a, from_bt(a));

printf(" b: %14s %10d\n", b, from_bt(b));

printf(" c: %14s %10d\n", c, from_bt(c));

printf("a*(b-c): %14s %10d\n", d, from_bt(d));

return 0;

}</lang>

{{out}}

<pre> a: +-0++0+ 523

b: -++-0-- -436

c: +-++- 65

a*(b-c): ----0+--0++0 -262023</pre>

<lang cpp>#include <iostream>