The Loptran computer dialect

Along with theory, illustrations, and discussion, I display the essential parts of the programs that created the illustrations. To reduce verbosity in these programs, my colleagues and I have invented a little language called Loptran, that is readily translated to Fortran 90. I believe readers without Fortran experience will comfortably be able to read Loptran, but they should consult a Fortran book if they plan to write it.

The name Loptran denotes Linear OPerator TRANslator. The limitation of Fortran 77 overcome by Fortran 90 and Loptran is that we can now isolate natural science application code from computer science least-squares fitting code, thus enabling practitioners in both disciplines to have more ready access to one anothers intellectual product.

Fortran is the original language shared by scientific computer applications. The people who invented C and UNIX also made Fortran more readable by their invention of Ratfor. We have taken the good ideas from Ratfor which gives Loptran much the syntax of modern languages like C++ and Java. We adopted Ratfor to Fortran 90 (Bob Clapp) and added a compact notation to facilitate linear operators (Sergey Fomel). Loptran is a small and simple adaptation of well-tested languages, and translates to one. Loptran is, however, new in 1998 and is not yet well tested. In this book, I avoid special features of Fortran to make everyone comfortable with Loptran as a generic algorithmic language that may some day be translated to other languages such as Java or Matlab.

We provide the Loptran translator free. It is written in another free language, PERL, and therefore should be available free to nearly everyone.