Plan 9 - man page for twig (plan9 section 1)
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twig - tree-manipulation language
twig [ -sASC ] [ -w suffix ] file.mt
Twig converts a tree-specification scheme consisting of pattern-action rules with associ-
ated costs into C functions that can be called to manipulate input trees. The C functions
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 pro-
gramming algorithm resolves any ambiguities by selecting a cheapest covering.
The input file containing the tree-specification scheme must have the suffix Twig produces
two output files: walker.c, which becomes the source file for the tree matcher, and sym-
bols.h, which contains the definitions for the node and label symbols used in the source
To build walker.c, twig uses an internal template file, by default one appropriate for use
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.
System area for template files.
S. W. K. Tjiang, ``The Twig Reference Manual'', Computing Science Technical Report No.
120, AT&T Bell Laboratories, Murray Hill, N.J.
A. V. Aho, M. Ganapathi, and S. W. K. Tjiang, ``Code generation using tree matching and
When tree matching fails, the debugging output is cryptic.
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