Type marshalling to call a fortran subroutine from C#

Question

I\'m trying to call a FORTRAN77 subroutine from C# code using P/invoke - in case you\'re interested, I\'m trying to wrap some of the functionality offered by the ARPACK library

Answer 1

1) Quoting Wikipedia:

Single precision, called "float" in the C language family, and "real" or "real*4" in Fortran. This is a binary format that occupies 32 bits (4 bytes) and its significand has a precision of 24 bits (about 7 decimal digits).

So marshal it as a float. You could have tested that one, it's either a float or a double.

2) Quoting this Fortran 77 Tutorial:

Fortran 77 uses the so-called call-by-reference paradigm. This means that instead of just passing the values of the function/subroutine arguments (call-by-value), the memory address of the arguments (pointers) are passed instead.

Pass every parameter by reference.