The XCParser module contains a parser (file) for .XCompose files and types for the representation.

The Extended module contains the same, with extensions to the syntax (and correspondingly to the representation types). Currently, there are three and a half extensions:

• Grouping with {} allows common prefixes to be factored out.
• Names can be defined with [name] in place of a sequence and referenced by @name as a target. A name may be defined more than once, in which case the corresponding targets are concatenated.
• Sequence elements can be string literals to indicate the keysyms corresponding to the individual characters of the string.
• Sequences can be empty.

Additionally, Extended contains a function standardize to convert it into the representation of a standard .XCompose file, using the types from XCParser, and a list of errors. Lines that reference undefined names will be missing and an appropriate error among those returned. XCParser contains a function unparse to convert a representation back into .XCompose format. These together allow converting from extended to standard format.

standardize.hs is a program that does this. It accepts an extcompose file on stdin and writes the converted version to stdout. Any errors are written to stderr. A return value of 1 indicates a parse error, 2 indicates there were errors during conversion.