m1—Simple Macro Processor

Contributed by Jon Bentley

The m1 program is a “little brother” to the m4 macro processor found on UNIX systems. It was originally published in the article m1: A Mini Macro Processor, in Computer Language, June 1990, Volume 7, Number 6, pages 47-61. This program was brought to my attention by Ozan Yigit. Jon Bentley kindly sent me his current version of the program, as well as an early draft of his article (I was having trouble getting a copy of the published one). A PostScript version of this paper is included with the example programs, available from O’Reilly’s FTP server (see the Preface). I wrote these introductory notes, and the program notes below. [A.R.]

A macro processor copies its input to its output, while performing several jobs. The tasks are:

  1. Define and expand macros. Macros have two parts, a name and a body. All occurrences of a macro’s name are replaced with the macro’s body.

  2. Include files. Special include directives in a data file are replaced with the contents of the named file. Includes can usually be nested, with one included file including another. Included files are processed for macros.

  3. Conditional text inclusion and exclusion. Different parts of the text can be included in the final output, often based upon whether a macro is or isn’t defined.

  4. Depending on the macro processor, comment lines can appear that will be removed from the final output.

If you’re a C or C++ programmer, you’re already familiar with the built-in preprocessor in those ...

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