F# special quotes? (##)

Question

I just ran across http://frankniemeyer.blogspot.com/2010/04/minimalistic-native-64-bit-array.html Which contains the line

(# \"sizeof !0\" type(\'T) : native         


        

Answer 1

It's inline IL (intermediate language) code. This construct is used internally by the F# team to implement bits of the F# core library you just can't do any other way. This code will admit a warning saying it shouldn't be used any where other than the F# core libraries, so you probably don't have to worry about it too much as it should never appear in production code.