TWIG(1) TWIG(1) NAME twig - tree-manipulation language SYNOPSIS twig [ -sASC ] [ -w suffix ] file.mt DESCRIPTION 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 one appropriate for use with fprintf(2). The options are -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 fprintf(2). -s Do not produce a symbols.h file. -w suffix Use the template file /sys/lib/twig/walker.suffix. FILES /sys/lib/twig System area for template files. SOURCE /sys/src/cmd/twig SEE ALSO yacc(1) S. W. K. Tjiang, ``The Twig Reference Manual'', Computing TWIG(1) TWIG(1) Science Technical Report No. 120, AT&T Bell Laboratories, Murray Hill, N.J. A. V. Aho, M. Ganapathi, and S. W. K. Tjiang, ``Code genera- tion using tree matching and dynamic programming.'' BUGS When tree matching fails, the debugging output is cryptic.