From c0bc7b6e2d090554c9d940bc3614e089a688503a Mon Sep 17 00:00:00 2001 From: Mattias Andrée Date: Thu, 3 Mar 2016 10:33:29 +0100 Subject: Add zabs, zadd, zdiv, zmod, zmodmul, zmodpow, zneg, zpow, zsub, and the newly introduced zmodsqr MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Signed-off-by: Mattias Andrée --- src/zsub.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 70 insertions(+) create mode 100644 src/zsub.c (limited to 'src/zsub.c') diff --git a/src/zsub.c b/src/zsub.c new file mode 100644 index 0000000..437e329 --- /dev/null +++ b/src/zsub.c @@ -0,0 +1,70 @@ +/* See LICENSE file for copyright and license details. */ +#include "internals" + +#include +#include + + +void +zsub_unsigned(z_t a, z_t b, z_t c) +{ + int magcmp = zcmpmag(b, c); + z_t s; + size_t i, n; + zahl_char_t carry[] = {0, 0}; + + if (magcmp <= 0) { + if (magcmp == 0) { + SET_SIGNUM(a, 0); + return; + } + if (a != c) + zset(a, c); + *subtrahend = *b; + } else { + if (a != b) + zset(a, b); + *subtrahend = *c; + } + + n = a->used < s->used ? a->used : s->used; + + for (i = 0; i < n; i++) { + carry[~i & 1] = carry[i & 1] ? (a->chars[i] <= s->chars[i]) : (a->chars[i] < s->chars[i]); + a->chars[i] -= s->chars[i]; + a->chars[i] -= carry[i & 1]; + } + + if (carry[i] & 1) { + while (!a->chars[i]) + a->chars[i++] = ZAHL_CHAR_MAX; + a->chars[i] -= 1; + } + SET_SIGNUM(a, magcmp); +} + +void +zsub(z_t a, z_t b, z_t c) +{ + if (b == c) { + SET_SIGNUM(a, 0); + } else if (zzero(b)) { + zneg(a, c); + } else if (zzero(c)) { + if (a != b) + zset(a, b); + } else if ((zsignum(b) | zsignum(c)) < 0) { + if (zsignum(b) < 0) { + if (zsignum(c) < 0) { + zsub_unsigned(a, c, b); + } else { + zadd_unsigned(a, b, c); + SET_SIGNUM(a, -zsignum(a)); + } + } else { + zadd_unsigned(a, b, c); + } + } else { + zsub_unsigned(a, b, c); + } +} -- cgit v1.2.3-70-g09d2