Definition of “==” operator for Double

Question

For some reason I was sneaking into the .NET Framework source for the class Double and found out that the declaration of == is:

public static bo         


        

Answer 1

I took a look at the CIL with JustDecompile. The inner == gets translated to the CIL ceq op code. In other words, it's primitive CLR equality.

I was curious to see if the C# compiler would reference ceq or the == operator when comparing two double values. In the trivial example I came up with (below), it used ceq.

This program:

void Main()
{
    double x = 1;
    double y = 2;

    if (x == y)
        Console.WriteLine("Something bad happened!");
    else
        Console.WriteLine("All is right with the world");
}

generates the following CIL (note the statement with label IL_0017):

IL_0000:  nop
IL_0001:  ldc.r8      00 00 00 00 00 00 F0 3F
IL_000A:  stloc.0     // x
IL_000B:  ldc.r8      00 00 00 00 00 00 00 40
IL_0014:  stloc.1     // y
IL_0015:  ldloc.0     // x
IL_0016:  ldloc.1     // y
IL_0017:  ceq
IL_0019:  stloc.2
IL_001A:  ldloc.2
IL_001B:  brfalse.s   IL_002A
IL_001D:  ldstr       "Something bad happened!"
IL_0022:  call        System.Console.WriteLine
IL_0027:  nop
IL_0028:  br.s        IL_0035
IL_002A:  ldstr       "All is right with the world"
IL_002F:  call        System.Console.WriteLine
IL_0034:  nop
IL_0035:  ret