3.3 astwalk.pl -- Flexible traversals of abstract syntax trees

author

Adrian Prantl <adrian@complang.tuwien.ac.at>

version

0.8.6-rc4

copyright

Copyright (C) 2008-2009 Adrian Prantl

license

See COPYING in the root folder of the SATIrE project

This module defines commonly-used transformation utilities for the AST exported by SATIrE. It represents an more flexible alternative to the transformation interface provided by module ast_transform.

[det]zip(+Tree, -Zipper)

Creates a new Zipper from Tree.

How to move around a tree and replace subtrees=branches?

At each node, we cut out a branch and replace it with a free variable <Gap>. The original branch is given as a separate argument, allowing us to bind the new branch to <Gap>.

In a way, this works just like Huet's zipper!

[det]unzip(?Zipper, ?Tree, ?Context)

Converts between the Zipper data structure and its contents.

[semidet]walk_to(+Zipper, +Context, -Zipper1)

[semidet]down(+Zipper, +BranchNum, -Zipper1)

Navigate downwards in the tree to child #BranchNum.

• Works also with lists.

[semidet]up(+Zipper, -Zipper1)

Navigate upwards in the tree.

[semidet]right(+Zipper, -Zipper1)

Navigate to the next sibling in a tree or a list.

[semidet]top(+Zipper, -Zipper1)

Navigate back to the root of our tree.

To be done

Could be implemented more efficiently, too

[nondet]goto_function(+Zipper, ?Template, +Zipper1)

find a function like Template in a project or file and return its body if there is only a declaration available, the declaration will be returned

[det]distance_from_root(+Zipper, -Distance)

Return the current distance from the root node

next_preorder(+Zipper, -Zipper)

To be done

change name to next_tdlr Return the ``next'' node in a left-to-right traversal fashion. Algorithm: (rechtssucher) try down(1) else while not try right() do up()