如何检查C#中的数字是正数还是负数？

Question

如何检查C#中的数字是正数还是负数？

Answer 1

bool positive = number > 0;
bool negative = number < 0;

Answer 2

当然没有人给出正确答案,

num != 0   // num is positive *or* negative!

Answer 3

OVERKILL!

public static class AwesomeExtensions
{
    public static bool IsPositive(this int number)
    {
        return number > 0;
    }

    public static bool IsNegative(this int number)
    {
        return number < 0;
    }

    public static bool IsZero(this int number)
    {
        return number == 0;
    }

    public static bool IsAwesome(this int number)
    {
        return IsNegative(number) && IsPositive(number) && IsZero(number);
    }
}

Answer 4

该Math.Sign方法是一条路可走.它将为负数返回-1,对于正数返回1,对于等于零的值返回0(即零没有符号).如果双精度变量和单精度变量等于NaN,则会引发异常(ArithmeticException).

Answer 5

num < 0 // number is negative

Answer 6

这是行业标准:

int is_negative(float num)
{
  char *p = (char*) malloc(20);
  sprintf(p, "%f", num);
  return p[0] == '-';
}

Answer 7

你的年轻人和你的幻想少于标志.

回到我的日子,我们不得不使用Math.abs(num) != num //number is negative!

Answer 8

    public static bool IsPositive<T>(T value)
        where T : struct, IComparable<T>
    {
        return value.CompareTo(default(T)) > 0;
    }

Answer 9

本机程序员的版本.对于小端系统,行为是正确的.

bool IsPositive(int number)
{
   bool result = false;
   IntPtr memory = IntPtr.Zero;
   try
   {
       memory = Marshal.AllocHGlobal(4);
       if (memory == IntPtr.Zero)
           throw new OutOfMemoryException();

       Marshal.WriteInt32(memory, number);

       result = (Marshal.ReadByte(memory, 3) & 0x80) == 0;
   }
   finally
   {
       if (memory != IntPtr.Zero)
           Marshal.FreeHGlobal(memory);
   }
   return result;
}

不要使用它.

Answer 10

if (num < 0) {
  //negative
}
if (num > 0) {
  //positive
}
if (num == 0) {
  //neither positive or negative,
}

或使用"else ifs"

Answer 11

对于32位有符号整数,例如System.Int32,int在C#中:

bool isNegative = (num & (1 << 31)) != 0;

Answer 12

public static bool IsNegative<T>(T value)
   where T : struct, IComparable<T>
{
    return value.CompareTo(default(T)) < 0;
}

Answer 13

您只需要比较值及其绝对值是否相等:

if (value == Math.abs(value))
    return "Positif"
else return "Negatif"

Answer 14

bool isNegative(int n) {
  int i;
  for (i = 0; i <= Int32.MaxValue; i++) {
    if (n == i) 
      return false;
  }
  return true;
}