elm.lua

-- Copyright 2006-2017 Mitchell mitchell.att.foicica.com. See LICENSE.
-- Elm LPeg lexer
-- Modified by Alex Suraci.
-- Adapted from Haskell LPeg lexer by Karl Schultheisz.

local l = require('lexer')
local token, word_match = l.token, l.word_match
local P, R, S = lpeg.P, lpeg.R, lpeg.S

local M = {_NAME = 'elm'}

-- Whitespace.
local ws = token(l.WHITESPACE, l.space^1)

-- Comments.
local line_comment = '--' * l.nonnewline_esc^0
local block_comment = '{-' * (l.any - '-}')^0 * P('-}')^-1
local comment = token(l.COMMENT, line_comment + block_comment)

-- Strings.
local string = token(l.STRING, l.delimited_range('"'))

-- Chars.
local char = token(l.STRING, l.delimited_range("'", true))

-- Numbers.
local number = token(l.NUMBER, l.float + l.integer)

-- Keywords.
local keyword = token(l.KEYWORD, word_match{
	'if', 'then', 'else',
	'case', 'of',
	'let', 'in',
	'module', 'import', 'as', 'exposing',
	'type', 'alias',
	'port',
})

-- Identifiers.
local word = (l.alnum + S("._'#"))^0
local identifier = token(l.IDENTIFIER, (l.alpha + '_') * word)

-- Operators.
local op = l.punct - S('()[]{}')
local operator = token(l.OPERATOR, op)

-- Types & type constructors.
local constructor = token(l.TYPE, (l.upper * word) + (P(":") * (op^1 - P(":"))))

M._rules = {
  {'whitespace', ws},
  {'keyword', keyword},
  {'type', constructor},
  {'identifier', identifier},
  {'string', string},
  {'char', char},
  {'comment', comment},
  {'number', number},
  {'operator', operator},
}

M._FOLDBYINDENTATION = true

return M