text: /*
  Language: Haskell
  Author: Jeremy Hull <sourdrums@gmail.com>
  Contributors: Zena Treep <zena.treep@gmail.com>
  Website: https://www.haskell.org
  Category: functional
  */
  
  export default function(hljs) {
    var COMMENT = {
      variants: [
        hljs.COMMENT('--', '$'),
        hljs.COMMENT(
          /\{-/,
          /-\}/,
          {
            contains: ['self']
          }
        )
      ]
    };
  
    var PRAGMA = {
      className: 'meta',
      begin: /\{-#/, end: /#-\}/
    };
  
    var PREPROCESSOR = {
      className: 'meta',
      begin: '^#', end: '$'
    };
  
    var CONSTRUCTOR = {
      className: 'type',
      begin: '\\b[A-Z][\\w\']*', // TODO: other constructors (build-in, infix).
      relevance: 0
    };
  
    var LIST = {
      begin: '\\(', end: '\\)',
      illegal: '"',
      contains: [
        PRAGMA,
        PREPROCESSOR,
        {className: 'type', begin: '\\b[A-Z][\\w]*(\\((\\.\\.|,|\\w+)\\))?'},
        hljs.inherit(hljs.TITLE_MODE, {begin: '[_a-z][\\w\']*'}),
        COMMENT
      ]
    };
  
    var RECORD = {
      begin: /\{/, end: /\}/,
      contains: LIST.contains
    };
  
    return {
      name: 'Haskell',
      aliases: ['hs'],
      keywords:
        'let in if then else case of where do module import hiding ' +
        'qualified type data newtype deriving class instance as default ' +
        'infix infixl infixr foreign export ccall stdcall cplusplus ' +
        'jvm dotnet safe unsafe family forall mdo proc rec',
      contains: [
  
        // Top-level constructions.
  
        {
          beginKeywords: 'module', end: 'where',
          keywords: 'module where',
          contains: [LIST, COMMENT],
          illegal: '\\W\\.|;'
        },
        {
          begin: '\\bimport\\b', end: '$',
          keywords: 'import qualified as hiding',
          contains: [LIST, COMMENT],
          illegal: '\\W\\.|;'
        },
  
        {
          className: 'class',
          begin: '^(\\s*)?(class|instance)\\b', end: 'where',
          keywords: 'class family instance where',
          contains: [CONSTRUCTOR, LIST, COMMENT]
        },
        {
          className: 'class',
          begin: '\\b(data|(new)?type)\\b', end: '$',
          keywords: 'data family type newtype deriving',
          contains: [PRAGMA, CONSTRUCTOR, LIST, RECORD, COMMENT]
        },
        {
          beginKeywords: 'default', end: '$',
          contains: [CONSTRUCTOR, LIST, COMMENT]
        },
        {
          beginKeywords: 'infix infixl infixr', end: '$',
          contains: [hljs.C_NUMBER_MODE, COMMENT]
        },
        {
          begin: '\\bforeign\\b', end: '$',
          keywords: 'foreign import export ccall stdcall cplusplus jvm ' +
                    'dotnet safe unsafe',
          contains: [CONSTRUCTOR, hljs.QUOTE_STRING_MODE, COMMENT]
        },
        {
          className: 'meta',
          begin: '#!\\/usr\\/bin\\/env\ runhaskell', end: '$'
        },
  
        // "Whitespaces".
  
        PRAGMA,
        PREPROCESSOR,
  
        // Literals and names.
  
        // TODO: characters.
        hljs.QUOTE_STRING_MODE,
        hljs.C_NUMBER_MODE,
        CONSTRUCTOR,
        hljs.inherit(hljs.TITLE_MODE, {begin: '^[_a-z][\\w\']*'}),
  
        COMMENT,
  
        {begin: '->|<-'} // No markup, relevance booster
      ]
    };
  }
  