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     TWIG(1)                                                   TWIG(1)

          twig - tree-manipulation language

          twig [ -sASC ] [ -w suffix ]

          Twig converts a tree-specification scheme consisting of
          pattern-action rules with associated costs into C functions
          that can be called to manipulate input trees.  The C func-
          tions first find a minimum-cost covering of an input tree
          using a dynamic programming algorithm and then execute the
          actions associated with the patterns used in the covering.
          The tree-specification scheme may allow several coverings
          for an input tree, but the dynamic programming algorithm
          resolves any ambiguities by selecting a cheapest covering.

          The input file containing the tree-specification scheme must
          have the suffix `.mt'.  Twig produces two output files:
          walker.c, which becomes the source file for the tree
          matcher, and symbols.h, which contains the definitions for
          the node and label symbols used in the source file.

          To build walker.c, twig uses an internal template file, by
          default on appropriate for use with fprintf(2). The options

          -A         Use a template file for ANSI/POSIX source files.

          -C         Use a template file for files that use libc's
                     print(2) routines.

          -S         Use a template file for files that use

          -s         Do not produce a symbols.h file.

          -w suffix  Use the template file

          /sys/lib/twig  System area for template files.

          S. W. K. Tjiang, The Twig Reference Manual, Computing Sci-
          ence Technical Report No. 120, AT&T Bell Laboratories, Mur-
          ray Hill, N.J.
          A. V. Aho, M. Ganapathi, and S. W. K. Tjiang, Code
          generation using tree matching and dynamic programming.

     TWIG(1)                                                   TWIG(1)

          When tree matching fails, the debugging output is cryptic.