c# - What is causing this to behave strangely? -

i'm working in environment absent double/math library (netmf). wrote class make things easier:

public struct doubleex {     public const double nan = 0.0d / 0.0d;     public static bool isnan(double x)     {         return x != x;     }     ... } 

seems should work, right?

well, when run code:

debug.print("method call: " + doubleex.isnan(doubleex.nan)); debug.print("method call: " + doubleex.nan != doubleex.nan); 

i output:

false true 

somehow, act of putting in function breaks it! there kind of optimization going on here? or hardware misinterpreting instructions?

the following based on ieee standard 754:

// @struct ieee_doublerep | allows bit access 8 byte floats //[structlayout(layoutkind.sequential)] //public struct ieee_doublerep //{ //    ulong low_mantissa;       // @field low 16 bits of mantissa //    ushort mid_mantissa;  // @field mid 16 bits of mantissa //    uint high_mantissa:4;     // @field high 4 bits of mantissa //    uint exponent:11;         // @field exponent of floating point number //    uint sign:1;              // @field sign of floating point number //};  public struct doubleex {     public const long nanmask = 0x7ff0000000000000;     public const long infinitymask = 0x000fffffffffffff;      public const double nan = 0.0f / 0.0f;     public const double negativeinfinity = -1.0f / 0.0f;     public const double positiveinfinity = 1.0f / 0.0f;     public static bool isnanbad(double x)     {         return x != x;     }      public unsafe static bool isnan(double value)             {         long rep = *((long*)&value);         return ((rep & nanmask) == nanmask &&                 ((rep & infinitymask) != 0));     }      public unsafe static bool ispositiveinfinity(double value)     {         double neginf = doubleex.positiveinfinity;         return *((long*)&value) == *((long*)&neginf);     }      public unsafe static bool isnegativeinfinity(double value)     {         double posinf = doubleex.positiveinfinity;         return *((long*)&value) == *((long*)&posinf);     }      public unsafe static bool isinfinite(double x)     {         long rep = *((long*)&x);         return ((rep & nanmask) == nanmask &&                 ((rep & infinitymask) == 0));     } }