Sather is an object oriented language which aims to be simple,
efficient, safe, and non-proprietary. It aims to meet the needs of
modern research groups and to foster the development of a large,
freely available, high-quality library of efficient well-written
classes for a wide variety of computational tasks. It was originally
based on Eiffel but now incorporates ideas and approaches from several
languages. One way of placing it in the "space of languages" is to say
that it attempts to be as efficient as C, C++, or Fortran, as elegant
and safe as Eiffel or CLU, and to support higher-order functions as
well as Common Lisp, Scheme, or Smalltalk.

Sather has garbage collection, statically-checked strong typing,
multiple inheritance, separate implementation and type inheritance,
parameterized classes, dynamic dispatch, iteration abstraction,
higher-order routines and iters, exception handling, assertions,
preconditions, postconditions, and class invariants.  Sather code can
be compiled into C code and can efficiently link with C object files.

Note: this version will work with non-threaded Tk only due to problems
with GC and threads!

WWW: http://www.gnu.org/software/sather/