The Loptran computer dialect

Along with theory, illustrations, and discussion, I display 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. Loptran is not a new language compiler but a simple text processor that expands concise scientific language into the more verbose expressions required by Fortran 90.

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. Sergey Fomel, Bob Clapp, and I have taken the good ideas from original Ratfor and merged them with concepts of linear operators to make Loptran, a language with much the syntax of modern languages like C++ and Java. 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 widely used.

To help make everyone comfortable with Loptran as a generic algorithmic language, this book avoids special features of Fortran. This should make it easier for some of you to translate to your favorite language, such as Matlab, Java, C, or C++.

We provide the Loptran translator free. It is written in another free language, PERL, and therefore should be available free to nearly everyone. If you prefer not to use Ratfor90 and Loptran, you can find on the WWW the Fortran 90 version of the programs in this book.