*Task*

Given a grammar and a parse tree obtained by parsing a term over this grammar, construct a subgrammar that still parses the same term.

*Description*

Given a grammar _G_ and a term _t_ over that grammar, a subgrammar that still parses _t_ can be obtained in the following steps.

	1. Parse _t_ over _G_, using Sdf.SdfToTable and sglrSGLR, to obtain a parse tree _t.asfix_.
	1. Run the parse tree trough asfix2sdfGT, to obtain your subgrammar, in _normalized_ Sdf form.
	1. Run the normalized subgrammar through sdfdenormalizeGT, to transfer the subgrammar into ordinary Sdf.
	1. Pretty-print the subgrammar.

*Examples*

Assume that L.def is an Sdf grammar for language L, and t is a term over L.

  # sdf2table -i L.def -o L.tbl
  # sglr -p L.tbl \
	 -i t \
	 -o t.asfix
  # asfix2sdf -i t.asfix \
	| sdf-de-normalize -o L.sub.def.af
  # sdf2text -a -i L.sub.def.af -o L.sub.def

*See Also*

Sdf.SdfToTable, sglrSGLR, asfix2sdfGT, sdfdenormalizeGT, HowToPrettyPrintAGrammar.