mello

No-fuss syntax with s-expressions

Parsing Diagnostics

Mello.Parse exposes two parsing entry points:

• parseSexp :: Text -> Either (Err Void) LocSexp preserves the original Looksee error API.
• parseSexpDetailed :: Text -> Either ParseErr LocSexp adds Mello-domain diagnostics before falling back to Looksee errors.

ParseErr classifies delimiter failures with source locations:

• ParseErrUnclosedList Brace LocSpan
• ParseErrUnexpectedClose Brace LocSpan
• ParseErrMismatchedBrace Brace LocSpan Brace LocSpan
• ParseErrLooksee LocSpan (Err Void)

ParseErrLooksee intentionally keeps the raw Looksee.Err while also carrying its span converted to LocSpan. This lets clients either render with Looksee or use Mello line/column locations without traversing Looksee internals.

For interactive use, parseSexpI prints Looksee parse errors and parseSexpDetailedI prints detailed delimiter errors or the underlying Looksee parse error.

Delimiter Recognition

Mello.Recognize provides a lightweight delimiter recognizer used by parseSexpDetailed:

• recognizeSexpText :: Text -> Either RecogErr ()
• sexpRecognizer :: Fold Char (Either RecogErr ())

The recognizer checks delimiter balance while respecting strings, chars, comments, and escapes. It does not parse s-expressions; it only reports offset-based delimiter errors:

• RecogErrUnclosedList Brace openOffset eofOffset
• RecogErrUnexpectedClose Brace closeOffset
• RecogErrMismatchedBrace expected openOffset actual closeOffset