Unparser

In computing, an unparser is a system that constructs a set of characters or image components from a given parse tree.^[1][2]

A parse tree, which generates "John hit the ball" when it is unparsed.

An unparser is in effect the reverse of a traditional parser that takes a set of string of characters and produces a parse tree. Unparsing generally involves the application of a specific set of rules to the parse tree as a "tree walk" takes place.^[1]

Given that the tree may involve both textual and graphic elements, the unparser may have two separate modules, each of which handles the relevant components.^[2] In such cases the "master unparser" looks up the "master unparse table" to determine if a given nested structure should be handled by one module, or the other.^[2]

See also

• Bidirectional transformation
• Formal grammar
• Natural language generation