[antlr-interest] Formatter Implementation

Alex Sedow alexsedow at mail.ru
Tue Jan 4 02:50:56 PST 2005

I try to write formatter which generates the program using a AST-tree. How
it is better for making? It is necessary to use AST-visitor or to write
corresponding function in each AST-node?

The basic problem with AST-visitor consists that AST-node can contain a
number of tokens and children. Each child can generate any number of tokens.
For example for-statement generates the following sequence of tokens:

"for" "(" initializer-tokens ";" condition-tokens ";" iterator-tokens ")"

The task of the formatter will consist in pasting tokens of the parent and
children and adding additional tokens like whitespace, newline, etc. The
variant with classical AST-visitor does not approach because each AST-node
is visited only once. Therefore I while have stopped on a variant with
expanded AST-visitor which in addition visits AST-node after each child. For
for-statement it will look so:

visit initializer
visit condition
visit iterator
visit statement

For full C# grammar it is rather bulky. About 500 functions in expanded

If somebody has experience in a writting formaters then please suggest idea.


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