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| author | Sebastiano Tronto <sebastiano@tronto.net> | 2024-12-21 18:13:27 +0100 |
|---|---|---|
| committer | Sebastiano Tronto <sebastiano@tronto.net> | 2024-12-21 18:13:27 +0100 |
| commit | 8ca27427af98bd3a82e8c5f4a199513295747930 (patch) | |
| tree | 6409e8f25209c5719ab17d158f242085b8d1fe9a /zmodn.h | |
| parent | 771667c2bb52235d6dacf67eab933207b59e167b (diff) | |
| download | zmodn-8ca27427af98bd3a82e8c5f4a199513295747930.tar.gz zmodn-8ca27427af98bd3a82e8c5f4a199513295747930.zip | |
Revert "Fix division"
Actually you cannot do division like that, the result is not unique.
This reverts commit 771667c2bb52235d6dacf67eab933207b59e167b.
Diffstat (limited to 'zmodn.h')
| -rw-r--r-- | zmodn.h | 8 |
1 files changed, 3 insertions, 5 deletions
| @@ -40,15 +40,13 @@ public: | |||
| 40 | bool operator!=(const Zmod& z) const { return value != z.value; } | 40 | bool operator!=(const Zmod& z) const { return value != z.value; } |
| 41 | 41 | ||
| 42 | std::optional<Zmod> inverse() const { | 42 | std::optional<Zmod> inverse() const { |
| 43 | auto [g, a, b] = extended_gcd(value, N); | 43 | auto [g, a, _] = extended_gcd(value, N); |
| 44 | return g == 1 ? Zmod(a) : std::optional<Zmod>{}; | 44 | return g == 1 ? Zmod(a) : std::optional<Zmod>{}; |
| 45 | } | 45 | } |
| 46 | 46 | ||
| 47 | std::optional<Zmod> operator/(const Zmod& d) const { | 47 | std::optional<Zmod> operator/(const Zmod& d) const { |
| 48 | auto [g, x, y] = extended_gcd(value, d.toint()); | 48 | auto i = d.inverse(); |
| 49 | auto [a, b] = std::pair<Zmod, Zmod>{value / g, d.toint() / g}; | 49 | return i ? (*this) * i.value() : i; |
| 50 | auto i = b.inverse(); | ||
| 51 | return i ? a * i.value() : i; | ||
| 52 | } | 50 | } |
| 53 | 51 | ||
| 54 | std::optional<Zmod> operator/=(const Zmod& d) { | 52 | std::optional<Zmod> operator/=(const Zmod& d) { |
