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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
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