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# C | Python > マイナス値のmodulo(%)演算 > C:マイナスを返す | Python:プラスを返す

Pythonで一定時間ごとに処理を実行する
の実装で以下のmodulo(%)演算はマイナス値が返ると思っていた自分がいました。

```next_time = ((base_time - time.time()) % interval) or interval
```

### C

https://ideone.com/cgMjRc

```#include <stdio.h>

int main(void) {
int val = -3;
printf("%d\n", val % 5);
return 0;
}
```
run
```-3
```

### Python 3.5

https://ideone.com/CMgBPa

```val=-3
print(val % 5)
```
run
```2
```

### 備考

Pythonをよく使う人は知っていることなのかもしれない。

https://docs.python.org/3/reference/expressions.html

The % (modulo) operator yields the remainder from the division of the first argument by the second. The numeric arguments are first converted to a common type. A zero right argument raises the ZeroDivisionError exception. The arguments may be floating point numbers, e.g., 3.14%0.7 equals 0.34 (since 3.14 equals 4*0.7 + 0.34.) The modulo operator always yields a result with the same sign as its second operand (or zero); the absolute value of the result is strictly smaller than the absolute value of the second operand