text: module.exports = function(hljs) {
    return {
      aliases: ['ml'],
      keywords: {
        keyword:
          /* according to Definition of Standard ML 97  */
          'abstype and andalso as case datatype do else end eqtype ' +
          'exception fn fun functor handle if in include infix infixr ' +
          'let local nonfix of op open orelse raise rec sharing sig ' +
          'signature struct structure then type val with withtype where while',
        built_in:
          /* built-in types according to basis library */
          'array bool char exn int list option order real ref string substring vector unit word',
        literal:
          'true false NONE SOME LESS EQUAL GREATER nil'
      },
      illegal: /\/\/|>>/,
      lexemes: '[a-z_]\\w*!?',
      contains: [
        {
          className: 'literal',
          begin: /\[(\|\|)?\]|\(\)/,
          relevance: 0
        },
        hljs.COMMENT(
          '\\(\\*',
          '\\*\\)',
          {
            contains: ['self']
          }
        ),
        { /* type variable */
          className: 'symbol',
          begin: '\'[A-Za-z_](?!\')[\\w\']*'
          /* the grammar is ambiguous on how 'a'b should be interpreted but not the compiler */
        },
        { /* polymorphic variant */
          className: 'type',
          begin: '`[A-Z][\\w\']*'
        },
        { /* module or constructor */
          className: 'type',
          begin: '\\b[A-Z][\\w\']*',
          relevance: 0
        },
        { /* don't color identifiers, but safely catch all identifiers with '*/
          begin: '[a-z_]\\w*\'[\\w\']*'
        },
        hljs.inherit(hljs.APOS_STRING_MODE, {className: 'string', relevance: 0}),
        hljs.inherit(hljs.QUOTE_STRING_MODE, {illegal: null}),
        {
          className: 'number',
          begin:
            '\\b(0[xX][a-fA-F0-9_]+[Lln]?|' +
            '0[oO][0-7_]+[Lln]?|' +
            '0[bB][01_]+[Lln]?|' +
            '[0-9][0-9_]*([Lln]|(\\.[0-9_]*)?([eE][-+]?[0-9_]+)?)?)',
          relevance: 0
        },
        {
          begin: /[-=]>/ // relevance booster
        }
      ]
    };
  };