How do I check if a number is positive or negative in C

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int j   num   -1   if  j - num     j            Num is equal to zero   else if  j  lt  i             Num is positive   else if  j  gt  i             Num is negative

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The Math Sign method is one way to go  It will return -1 for negative numbers  1 for positive numbers  and 0 for values equal to zero  i e  zero has no sign   Double and single precision variables will cause an exception  ArithmeticException  to be thrown if they equal NaN

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You youngins and your fancy less-than signs   Back in my day we had to use Math abs num     num   number is negative

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public static bool IsNegative lt T gt  T value     where T   struct  IComparable lt T gt        return value CompareTo default T    lt  0

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This code takes advantage of SIMD instructions to improve performance   public static bool IsPositive int n      var v   new Vector lt int gt  n     var result   Vector GreaterThanAll v  Vector lt int gt  Zero     return result

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num  lt  0    number is negative

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This is the industry standard   int is negative float num      char  p    char   malloc 20     sprintf p    f   num     return p 0      -

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bool positive   number  gt  0  bool negative   number  lt  0

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First parameter is stored in EAX register and result also   function IsNegative ANum  Integer   LongBool  assembler  asm    and eax   80000000 end

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For a 32-bit signed integer  such as System Int32  aka int in C    bool isNegative    num  amp   1  lt  lt  31      0

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public static bool IsPositive lt T gt  T value          where T   struct  IComparable lt T gt                return value CompareTo default T    gt  0

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Of course no-one s actually given the correct answer   num    0      num is positive  or  negative

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You just have to compare if the value  amp  its absolute value are equal   if  value    Math abs value       return  Positif  else return  Negatif

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OVERKILL   public static class AwesomeExtensions       public static bool IsPositive this int number                return number  gt  0             public static bool IsNegative this int number                return number  lt  0             public static bool IsZero this int number                return number    0             public static bool IsAwesome this int number                return IsNegative number   amp  amp  IsPositive number   amp  amp  IsZero number

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Native programmer s version  Behaviour is correct for little-endian systems   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   amp  0x80     0          finally             if  memory    IntPtr Zero             Marshal FreeHGlobal memory           return result      Do not ever use this

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if  num  lt  0        negative   if  num  gt  0        positive   if  num    0        neither positive or negative      or use  else ifs

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bool isNegative int n      int i    for  i   0  i  lt   Int32 MaxValue  i          if  n    i         return false        return true

[c#] How do I check if a number is positive or negative in C#?

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