Existing solutions

Examples

• Lexer.hs (in Haskell, from the Programatica front-end, ~500 lines) (originally from the hssource library supplied with GHC)
• GHC's lexer (in nonstandard Haskell, ~1300 lines)
• NHC's lexer (in Haskell, ~1200 lines)
• HBC's lexer (in C, ~1700 lines)
• Hugs' lexer (in C, ~2000 lines)