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# grammar::me::util(n) 0.2 tcllib "Grammar operations and usage"

## Name

grammar::me::util - AST utilities

## Synopsis

- package require Tcl 8.5 9
- package require grammar::me::util ?0.2?

- ::grammar::me::util::ast2tree ast tree ?root?
- ::grammar::me::util::ast2etree ast mcmd tree ?root?
- mcmd lc location
- mcmd tok from ?to?
- ::grammar::me::util::tree2ast tree ?root?

## Description

This package provides a number of utility command for the conversion between the various representations of abstract syntax trees as specified in the document grammar::me_ast.

::grammar::me::util::ast2tree ast tree ?root?

  This command converts an ast from value to object representation. All nodes in the ast will be converted into nodes of this tree, with the root of the AST a child of the node root. If this node is not explicitly specified the root of the tree is used. Existing content of tree is not touched, i.e. neither removed nor changed, with the exception of the specified root node, which will gain a new child.

::grammar::me::util::ast2etree ast mcmd tree ?root?

  This command is like ::grammar::me::util::ast2tree, except that the result is in the extended object representation of the input AST. The source of the extended information is the command prefix mcmd. It has to understand two methods, lc, and tok, with the semantics specified below.

  mcmd lc location

    Takes the location of a token given as offset in the input stream and return a 2-element list containing the associated line number and column index, in this order.

  mcmd tok from ?to?

    Takes one or two locations from and to as offset in the input stream and returns a Tcl list containing the specified part of the input stream. Both location are inclusive. If to is not specified it will default to the value of from.

    Each element of the returned list is a list containing the token, its associated lexeme, the line number, and column index, in this order.

  Both the ensemble command ::grammar::me::tcl provided by the package grammar::me::tcl and the objects command created by the package ::grammar::me::cpu fit the above specification.

::grammar::me::util::tree2ast tree ?root?

  This command converts an ast in (extended) object representation into a value and returns it. If a root node is specified the AST is generated from that node downward. Otherwise the root of the tree object is used as the starting point.

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category grammar_me of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.

## Keywords

abstract syntax tree, syntax tree, tree

## Category

Grammars and finite automata

## Copyright

Copyright © 2005 Andreas Kupries <andreas_kupries@users.sourceforge.net>