local len, match = string.len, string.match local expr_lexer = {} local lexer_mt = { __index = expr_lexer, } local literal_chars = {['('] = 1, [')'] = 1, ['~'] = 1, [','] = 1, ['|'] = 1, [':'] = 1} local oper_table = {['+'] = 2, ['-'] = 2, ['*'] = 3, ['/'] = 3, ['^'] = 4, ['!='] = 1, ['='] = 1, ['>'] = 1, ['>='] = 1, ['<'] = 1, ['<='] = 1, ['and'] = 0, ['or'] = 0, ['%'] = -1} local word_operators = {'and', 'or'} local multi_char_operators = {'!=', '>=', '<='} expr_lexer.operators = oper_table expr_lexer.max_oper_prio = 4 local oper_start_sym local function compile_oper_pattern() local oper_start_set = {} for k in pairs(oper_table) do oper_start_set[k:sub(1,1)] = true end oper_start_sym = '[' for k in pairs(oper_start_set) do local str = (k == '-' or k == '%' or k == '^') and ('%' .. k) or k oper_start_sym = oper_start_sym .. str end oper_start_sym = oper_start_sym .. ']' end function expr_lexer.new(src) local lexer = {n = 1, src=" src}" setmetatable(lexer, lexer_mt) lexer:next() return lexer end function expr_lexer.char(lexer) local n = lexer.n return lexer.src:sub(n, n) end function expr_lexer.incr(lexer, n) lexer.n_current = lexer.n lexer.n = lexer.n + (n or 1) end function expr_lexer.match(lexer, pattern) return match(lexer.src, '^' .. pattern, lexer.n) end function expr_lexer.consume(lexer, pattern) local m = match(lexer.src, '^' .. pattern, lexer.n) if m then lexer.n_current = lexer.n lexer.n = lexer.n + len(m) return m end end function expr_lexer.skip(lexer, pattern) local m = match(lexer.src, '^' .. pattern, lexer.n) if m then lexer.n = lexer.n + len(m) end end local function consume_oper(lexer, c) local op for i, ops in ipairs(word_operators) do if lexer:match(ops .. '[^%l%u_]') then lexer:consume(ops) op = ops break end end if not op then for i, ops in ipairs(multi_char_operators) do if lexer:match(ops) then lexer:consume(ops) op = ops break end end end if not op then op = oper_table[c] and c if op then lexer:incr() end end if op then local prio = oper_table[op] return {type= 'operator', symbol= op, priority = prio} end end function expr_lexer.next_token(lexer) lexer:skip('%s*') if lexer.n> len(lexer.src) then return {type= 'EOF'} end local c = lexer:char() if c == '\'' then local str = lexer:consume("'[^']+'") return {type= 'literal', value = str:sub(2, -2)} end if c == '[' then local str = lexer:consume('%b[]') return {type= 'ident', value= str:sub(2,-2)} end if lexer:match(oper_start_sym) then local elt = consume_oper(lexer, c) if elt then return elt end end if literal_chars[c] then lexer:incr() return {type= c} end if lexer:match('[%l%u_]') then local str = lexer:consume('[%l%u_][%l%u%d_.$]*') return {type= 'ident', value= str} end if lexer:match('%d') then local str = lexer:consume('%d+%.%d*[Ee]%+?%d+') str = str or lexer:consume('%d+%.%d*[Ee]%-?%d+') str = str or lexer:consume('%d+%.%d*') str = str or lexer:consume('%d+') return {type= 'number', value= tonumber(str)} end lexer:local_error("syntax error in expression:", lexer.n) end function expr_lexer.next(lexer) lexer.token = lexer:next_token() end function expr_lexer.local_error(lexer, msg, n_pos) n_pos = n_pos or lexer.n_current local line = string.format(' %s', lexer.src) local pos = string.format(' %s^', string.rep(' ', n_pos - 1)) error(string.format("%s\n%s\n%s", msg, line, pos)) end compile_oper_pattern() return expr_lexer