🚀 go-pugleaf

I think another characteristic of a good interface is how easy it is
to express that interface in different programming languages.  This
is because the 'abstraction' is a good match for the problem, and
therefore it is easy to express the 'abstraction' in an arbitrary
programming language.  Some examples taken from my recent experience
with POSIX.1 and Ada:

	-  each API operation should perform only 1 abstract function
		-- counter-example:  Unix fcntl()

	-  there should be a consistent use of types and values
		-- counter-example:  C functions that return 
		   a pointer, but return "-1" for an error

	-  error handling models should localize the effects of
	   errors
		-- the shared variable 'errno' causes problems in 
		   multi-threaded programs (both C and Ada)

I tend to be of the "it's best expressed in Ada" religion, but I've
found that it *is* possible to express good interfaces in C, FORTRAN
and even BASIC.  One thing the current move towards language
independence might do is help develop interfaces that can support
different software paradigms.

Right now I'm working on a binding to another system (defined in terms
of its C language API), and this system is much less easy to express
in Ada than the POSIX API was.  

				dave