GAWK: Effective AWK Programming

Appendix C: Implementation Notes 299Compilation of awk programsgawk uses a Bison (YACC-like) parser to convert the script given it into asyntax tree; the syntax tree is then executed by a simple recursive evaluator.This method incurs a lot of overhead, since the recursive evaluator performsmany procedure calls to do even the simplest things.It should be possible for gawk to convert the script’s parse tree into a C programwhich the user would then compile, using the normal C compiler and a specialgawk library to provide all the needed functions (regexps, fields, associativearrays, type coercion, and so on).An easier possibility might be for an intermediate phase of gawk to convert theparse tree into a linear byte code form like the one used in GNU Emacs Lisp.The recursive evaluator would then be replaced by a straight line byte codeinterpreter that would be intermediate in speed between running a compiledprogram and doing what gawk does now.Finally, the programs in the test suite could use documenting in this book.See Section C.2 [Making Additions to gawk], page 284, if you are interested in tacklingany of these projects.