Happy
Happy is a parser generator for Haskell that creates efficient parsers from context-free grammars, similar to tools like Yacc or Bison for other languages. It allows developers to define grammars in a BNF-like notation and generates Haskell code for parsing, making it easier to build compilers, interpreters, or other language-processing applications in Haskell.
Developers should learn Happy when working on projects that involve parsing complex text or language structures in Haskell, such as creating domain-specific languages, compilers, or data format processors. It is particularly useful for ensuring correct and efficient parsing without manually writing low-level parser code, saving time and reducing errors in language implementation tasks.