page_util_peg -
page PEG transformation utilities
package require page::util::peg ? 0.1 ?
package require snit
::page::util::peg::symbolNodeOf tree node
::page::util::peg::symbolOf tree node
::page::util::peg::updateUndefinedDueRemoval tree
::page::util::peg::flatten treequery tree
::page::util::peg::getWarnings tree
::page::util::peg::printWarnings msg
::page::util::peg::peOf tree eroot
::page::util::peg::printTclExpr pe
This package provides a few common operations to PEG transformations.
They assume a Normalized PE Grammar Tree as input, see the
package page::util::norm::peg, possibly augmented with
attributes coming from transformations not in conflict with the base
definition.
-
::page::util::peg::symbolNodeOf tree node
-
Given an arbitrary expression node in the AST tree it
determines the node (itself or an ancestor) containing the name of the
nonterminal symbol the node belongs to, and returns its id. The result
is either the root of the tree (for the start expression), or a
definition node.
-
::page::util::peg::symbolOf tree node
-
As ::page::util::peg::symbolNodeOf, but returns the symbol name
instead of the node.
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::page::util::peg::updateUndefinedDueRemoval tree
-
The removal of nodes in the AST tree can cause symbols to lose
one or more users.
A used by B and C,
B is reachable,
C is not,
so A now loses the node in the expression for C calling it,
or rather, not calling it anymore.
This command updates the cross-references and which nonterminals are
now undefined.
-
::page::util::peg::flatten treequery tree
-
This commands flattens nested sequence and choice operators in the AST
tree, re-using the treeql object treequery to
run the query determining which nodes to cut.
-
::page::util::peg::getWarnings tree
-
This command looks at the attributes of the AST tree for
problems with the grammar and issues warnings. They do not prevent us
from writing the grammar, but still represent problems with it the
user should be made aware of.
The result of the command is a dictionary mapping nonterminal names to
their associated warnings.
-
::page::util::peg::printWarnings msg
-
The argument of the command is a dictionary mapping nonterminal names
to their associated warnings, as generated by, for example, the
command ::page::util::peg::getWarnings.
The warnings contained therein are formatted and then printed via the
log command page_info. This means that this command can be used
only from within a plugin managed by the package
page::pluginmgr.
-
::page::util::peg::peOf tree eroot
-
This command converts the parsing expression starting at the node
eroot in the AST tree into a nested list. The exact syntax
of this list specified by the package grammar::peg.
-
::page::util::peg::printTclExpr pe
-
This command converts the parsing expression contained in the nested
list pe into a Tcl string which can be placed into a Tcl script.
See the package grammar::peg for the exact syntax of
pe.
This document, will undoubtedly contain bugs and other problems.
Please report such in the category
page of the
http://sourceforge.net/tracker/?group_id=12883.
Please also report any ideas for enhancements you may have.
page, parsing expression grammar, parser generator, text processing, PEG, transformation