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sre_parse.py
# # Secret Labs' Regular Expression Engine # # convert re-style regular expression to sre pattern # # Copyright (c) 1998-2001 by Secret Labs AB. All rights reserved. # # See the sre.py file for information on usage and redistribution. # """Internal support module for sre""" # XXX: show string offset and offending character for all errors from sre_constants import * SPECIAL_CHARS = ".\\[{()*+?^$|" REPEAT_CHARS = "*+?{" DIGITS = frozenset("0123456789") OCTDIGITS = frozenset("01234567") HEXDIGITS = frozenset("0123456789abcdefABCDEF") ASCIILETTERS = frozenset("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ") WHITESPACE = frozenset(" \t\n\r\v\f") _REPEATCODES = frozenset({MIN_REPEAT, MAX_REPEAT}) _UNITCODES = frozenset({ANY, RANGE, IN, LITERAL, NOT_LITERAL, CATEGORY}) ESCAPES = { r"\a": (LITERAL, ord("\a")), r"\b": (LITERAL, ord("\b")), r"\f": (LITERAL, ord("\f")), r"\n": (LITERAL, ord("\n")), r"\r": (LITERAL, ord("\r")), r"\t": (LITERAL, ord("\t")), r"\v": (LITERAL, ord("\v")), r"\\": (LITERAL, ord("\\")) } CATEGORIES = { r"\A": (AT, AT_BEGINNING_STRING), # start of string r"\b": (AT, AT_BOUNDARY), r"\B": (AT, AT_NON_BOUNDARY), r"\d": (IN, [(CATEGORY, CATEGORY_DIGIT)]), r"\D": (IN, [(CATEGORY, CATEGORY_NOT_DIGIT)]), r"\s": (IN, [(CATEGORY, CATEGORY_SPACE)]), r"\S": (IN, [(CATEGORY, CATEGORY_NOT_SPACE)]), r"\w": (IN, [(CATEGORY, CATEGORY_WORD)]), r"\W": (IN, [(CATEGORY, CATEGORY_NOT_WORD)]), r"\Z": (AT, AT_END_STRING), # end of string } FLAGS = { # standard flags "i": SRE_FLAG_IGNORECASE, "L": SRE_FLAG_LOCALE, "m": SRE_FLAG_MULTILINE, "s": SRE_FLAG_DOTALL, "x": SRE_FLAG_VERBOSE, # extensions "a": SRE_FLAG_ASCII, "t": SRE_FLAG_TEMPLATE, "u": SRE_FLAG_UNICODE, } GLOBAL_FLAGS = (SRE_FLAG_ASCII | SRE_FLAG_LOCALE | SRE_FLAG_UNICODE | SRE_FLAG_DEBUG | SRE_FLAG_TEMPLATE) class Verbose(Exception): pass class Pattern: # master pattern object. keeps track of global attributes def __init__(self): self.flags = 0 self.groupdict = {} self.groupwidths = [None] # group 0 self.lookbehindgroups = None @property def groups(self): return len(self.groupwidths) def opengroup(self, name=None): gid = self.groups self.groupwidths.append(None) if self.groups > MAXGROUPS: raise error("too many groups") if name is not None: ogid = self.groupdict.get(name, None) if ogid is not None: raise error("redefinition of group name %r as group %d; " "was group %d" % (name, gid, ogid)) self.groupdict[name] = gid return gid def closegroup(self, gid, p): self.groupwidths[gid] = p.getwidth() def checkgroup(self, gid): return gid < self.groups and self.groupwidths[gid] is not None def checklookbehindgroup(self, gid, source): if self.lookbehindgroups is not None: if not self.checkgroup(gid): raise source.error('cannot refer to an open group') if gid >= self.lookbehindgroups: raise source.error('cannot refer to group defined in the same ' 'lookbehind subpattern') class SubPattern: # a subpattern, in intermediate form def __init__(self, pattern, data=None): self.pattern = pattern if data is None: data = [] self.data = data self.width = None def dump(self, level=0): nl = True seqtypes = (tuple, list) for op, av in self.data: print(level*" " + str(op), end='') if op is IN: # member sublanguage print() for op, a in av: print((level+1)*" " + str(op), a) elif op is BRANCH: print() for i, a in enumerate(av[1]): if i: print(level*" " + "OR") a.dump(level+1) elif op is GROUPREF_EXISTS: condgroup, item_yes, item_no = av print('', condgroup) item_yes.dump(level+1) if item_no: print(level*" " + "ELSE") item_no.dump(level+1) elif isinstance(av, seqtypes): nl = False for a in av: if isinstance(a, SubPattern): if not nl: print() a.dump(level+1) nl = True else: if not nl: print(' ', end='') print(a, end='') nl = False if not nl: print() else: print('', av) def __repr__(self): return repr(self.data) def __len__(self): return len(self.data) def __delitem__(self, index): del self.data[index] def __getitem__(self, index): if isinstance(index, slice): return SubPattern(self.pattern, self.data[index]) return self.data[index] def __setitem__(self, index, code): self.data[index] = code def insert(self, index, code): self.data.insert(index, code) def append(self, code): self.data.append(code) def getwidth(self): # determine the width (min, max) for this subpattern if self.width is not None: return self.width lo = hi = 0 for op, av in self.data: if op is BRANCH: i = MAXREPEAT - 1 j = 0 for av in av[1]: l, h = av.getwidth() i = min(i, l) j = max(j, h) lo = lo + i hi = hi + j elif op is CALL: i, j = av.getwidth() lo = lo + i hi = hi + j elif op is SUBPATTERN: i, j = av[-1].getwidth() lo = lo + i hi = hi + j elif op in _REPEATCODES: i, j = av[2].getwidth() lo = lo + i * av[0] hi = hi + j * av[1] elif op in _UNITCODES: lo = lo + 1 hi = hi + 1 elif op is GROUPREF: i, j = self.pattern.groupwidths[av] lo = lo + i hi = hi + j elif op is GROUPREF_EXISTS: i, j = av[1].getwidth() if av[2] is not None: l, h = av[2].getwidth() i = min(i, l) j = max(j, h) else: i = 0 lo = lo + i hi = hi + j elif op is SUCCESS: break self.width = min(lo, MAXREPEAT - 1), min(hi, MAXREPEAT) return self.width class Tokenizer: def __init__(self, string): self.istext = isinstance(string, str) self.string = string if not self.istext: string = str(string, 'latin1') self.decoded_string = string self.index = 0 self.next = None self.__next() def __next(self): index = self.index try: char = self.decoded_string[index] except IndexError: self.next = None return if char == "\\": index += 1 try: char += self.decoded_string[index] except IndexError: raise error("bad escape (end of pattern)", self.string, len(self.string) - 1) from None self.index = index + 1 self.next = char def match(self, char): if char == self.next: self.__next() return True return False def get(self): this = self.next self.__next() return this def getwhile(self, n, charset): result = '' for _ in range(n): c = self.next if c not in charset: break result += c self.__next() return result def getuntil(self, terminator): result = '' while True: c = self.next self.__next() if c is None: if not result: raise self.error("missing group name") raise self.error("missing %s, unterminated name" % terminator, len(result)) if c == terminator: if not result: raise self.error("missing group name", 1) break result += c return result @property def pos(self): return self.index - len(self.next or '') def tell(self): return self.index - len(self.next or '') def seek(self, index): self.index = index self.__next() def error(self, msg, offset=0): return error(msg, self.string, self.tell() - offset) def _class_escape(source, escape): # handle escape code inside character class code = ESCAPES.get(escape) if code: return code code = CATEGORIES.get(escape) if code and code[0] is IN: return code try: c = escape[1:2] if c == "x": # hexadecimal escape (exactly two digits) escape += source.getwhile(2, HEXDIGITS) if len(escape) != 4: raise source.error("incomplete escape %s" % escape, len(escape)) return LITERAL, int(escape[2:], 16) elif c == "u" and source.istext: # unicode escape (exactly four digits) escape += source.getwhile(4, HEXDIGITS) if len(escape) != 6: raise source.error("incomplete escape %s" % escape, len(escape)) return LITERAL, int(escape[2:], 16) elif c == "U" and source.istext: # unicode escape (exactly eight digits) escape += source.getwhile(8, HEXDIGITS) if len(escape) != 10: raise source.error("incomplete escape %s" % escape, len(escape)) c = int(escape[2:], 16) chr(c) # raise ValueError for invalid code return LITERAL, c elif c in OCTDIGITS: # octal escape (up to three digits) escape += source.getwhile(2, OCTDIGITS) c = int(escape[1:], 8) if c > 0o377: raise source.error('octal escape value %s outside of ' 'range 0-0o377' % escape, len(escape)) return LITERAL, c elif c in DIGITS: raise ValueError if len(escape) == 2: if c in ASCIILETTERS: raise source.error('bad escape %s' % escape, len(escape)) return LITERAL, ord(escape[1]) except ValueError: pass raise source.error("bad escape %s" % escape, len(escape)) def _escape(source, escape, state): # handle escape code in expression code = CATEGORIES.get(escape) if code: return code code = ESCAPES.get(escape) if code: return code try: c = escape[1:2] if c == "x": # hexadecimal escape escape += source.getwhile(2, HEXDIGITS) if len(escape) != 4: raise source.error("incomplete escape %s" % escape, len(escape)) return LITERAL, int(escape[2:], 16) elif c == "u" and source.istext: # unicode escape (exactly four digits) escape += source.getwhile(4, HEXDIGITS) if len(escape) != 6: raise source.error("incomplete escape %s" % escape, len(escape)) return LITERAL, int(escape[2:], 16) elif c == "U" and source.istext: # unicode escape (exactly eight digits) escape += source.getwhile(8, HEXDIGITS) if len(escape) != 10: raise source.error("incomplete escape %s" % escape, len(escape)) c = int(escape[2:], 16) chr(c) # raise ValueError for invalid code return LITERAL, c elif c == "0": # octal escape escape += source.getwhile(2, OCTDIGITS) return LITERAL, int(escape[1:], 8) elif c in DIGITS: # octal escape *or* decimal group reference (sigh) if source.next in DIGITS: escape += source.get() if (escape[1] in OCTDIGITS and escape[2] in OCTDIGITS and source.next in OCTDIGITS): # got three octal digits; this is an octal escape escape += source.get() c = int(escape[1:], 8) if c > 0o377: raise source.error('octal escape value %s outside of ' 'range 0-0o377' % escape, len(escape)) return LITERAL, c # not an octal escape, so this is a group reference group = int(escape[1:]) if group < state.groups: if not state.checkgroup(group): raise source.error("cannot refer to an open group", len(escape)) state.checklookbehindgroup(group, source) return GROUPREF, group raise source.error("invalid group reference %d" % group, len(escape) - 1) if len(escape) == 2: if c in ASCIILETTERS: raise source.error("bad escape %s" % escape, len(escape)) return LITERAL, ord(escape[1]) except ValueError: pass raise source.error("bad escape %s" % escape, len(escape)) def _parse_sub(source, state, verbose, nested): # parse an alternation: a|b|c items = [] itemsappend = items.append sourcematch = source.match start = source.tell() while True: itemsappend(_parse(source, state, verbose, nested + 1, not nested and not items)) if not sourcematch("|"): break if len(items) == 1: return items[0] subpattern = SubPattern(state) subpatternappend = subpattern.append # check if all items share a common prefix while True: prefix = None for item in items: if not item: break if prefix is None: prefix = item[0] elif item[0] != prefix: break else: # all subitems start with a common "prefix". # move it out of the branch for item in items: del item[0] subpatternappend(prefix) continue # check next one break # check if the branch can be replaced by a character set for item in items: if len(item) != 1 or item[0][0] is not LITERAL: break else: # we can store this as a character set instead of a # branch (the compiler may optimize this even more) subpatternappend((IN, [item[0] for item in items])) return subpattern subpattern.append((BRANCH, (None, items))) return subpattern def _parse_sub_cond(source, state, condgroup, verbose, nested): item_yes = _parse(source, state, verbose, nested + 1) if source.match("|"): item_no = _parse(source, state, verbose, nested + 1) if source.next == "|": raise source.error("conditional backref with more than two branches") else: item_no = None subpattern = SubPattern(state) subpattern.append((GROUPREF_EXISTS, (condgroup, item_yes, item_no))) return subpattern def _parse(source, state, verbose, nested, first=False): # parse a simple pattern subpattern = SubPattern(state) # precompute constants into local variables subpatternappend = subpattern.append sourceget = source.get sourcematch = source.match _len = len _ord = ord while True: this = source.next if this is None: break # end of pattern if this in "|)": break # end of subpattern sourceget() if verbose: # skip whitespace and comments if this in WHITESPACE: continue if this == "#": while True: this = sourceget() if this is None or this == "\n": break continue if this[0] == "\\": code = _escape(source, this, state) subpatternappend(code) elif this not in SPECIAL_CHARS: subpatternappend((LITERAL, _ord(this))) elif this == "[": here = source.tell() - 1 # character set set = [] setappend = set.append ## if sourcematch(":"): ## pass # handle character classes if sourcematch("^"): setappend((NEGATE, None)) # check remaining characters start = set[:] while True: this = sourceget() if this is None: raise source.error("unterminated character set", source.tell() - here) if this == "]" and set != start: break elif this[0] == "\\": code1 = _class_escape(source, this) else: code1 = LITERAL, _ord(this) if sourcematch("-"): # potential range that = sourceget() if that is None: raise source.error("unterminated character set", source.tell() - here) if that == "]": if code1[0] is IN: code1 = code1[1][0] setappend(code1) setappend((LITERAL, _ord("-"))) break if that[0] == "\\": code2 = _class_escape(source, that) else: code2 = LITERAL, _ord(that) if code1[0] != LITERAL or code2[0] != LITERAL: msg = "bad character range %s-%s" % (this, that) raise source.error(msg, len(this) + 1 + len(that)) lo = code1[1] hi = code2[1] if hi < lo: msg = "bad character range %s-%s" % (this, that) raise source.error(msg, len(this) + 1 + len(that)) setappend((RANGE, (lo, hi))) else: if code1[0] is IN: code1 = code1[1][0] setappend(code1) # XXX: <fl> should move set optimization to compiler! if _len(set)==1 and set[0][0] is LITERAL: subpatternappend(set[0]) # optimization elif _len(set)==2 and set[0][0] is NEGATE and set[1][0] is LITERAL: subpatternappend((NOT_LITERAL, set[1][1])) # optimization else: # XXX: <fl> should add charmap optimization here subpatternappend((IN, set)) elif this in REPEAT_CHARS: # repeat previous item here = source.tell() if this == "?": min, max = 0, 1 elif this == "*": min, max = 0, MAXREPEAT elif this == "+": min, max = 1, MAXREPEAT elif this == "{": if source.next == "}": subpatternappend((LITERAL, _ord(this))) continue min, max = 0, MAXREPEAT lo = hi = "" while source.next in DIGITS: lo += sourceget() if sourcematch(","): while source.next in DIGITS: hi += sourceget() else: hi = lo if not sourcematch("}"): subpatternappend((LITERAL, _ord(this))) source.seek(here) continue if lo: min = int(lo) if min >= MAXREPEAT: raise OverflowError("the repetition number is too large") if hi: max = int(hi) if max >= MAXREPEAT: raise OverflowError("the repetition number is too large") if max < min: raise source.error("min repeat greater than max repeat", source.tell() - here) else: raise AssertionError("unsupported quantifier %r" % (char,)) # figure out which item to repeat if subpattern: item = subpattern[-1:] else: item = None if not item or (_len(item) == 1 and item[0][0] is AT): raise source.error("nothing to repeat", source.tell() - here + len(this)) if item[0][0] in _REPEATCODES: raise source.error("multiple repeat", source.tell() - here + len(this)) if sourcematch("?"): subpattern[-1] = (MIN_REPEAT, (min, max, item)) else: subpattern[-1] = (MAX_REPEAT, (min, max, item)) elif this == ".": subpatternappend((ANY, None)) elif this == "(": start = source.tell() - 1 group = True name = None condgroup = None add_flags = 0 del_flags = 0 if sourcematch("?"): # options char = sourceget() if char is None: raise source.error("unexpected end of pattern") if char == "P": # python extensions if sourcematch("<"): # named group: skip forward to end of name name = source.getuntil(">") if not name.isidentifier(): msg = "bad character in group name %r" % name raise source.error(msg, len(name) + 1) elif sourcematch("="): # named backreference name = source.getuntil(")") if not name.isidentifier(): msg = "bad character in group name %r" % name raise source.error(msg, len(name) + 1) gid = state.groupdict.get(name) if gid is None: msg = "unknown group name %r" % name raise source.error(msg, len(name) + 1) if not state.checkgroup(gid): raise source.error("cannot refer to an open group", len(name) + 1) state.checklookbehindgroup(gid, source) subpatternappend((GROUPREF, gid)) continue else: char = sourceget() if char is None: raise source.error("unexpected end of pattern") raise source.error("unknown extension ?P" + char, len(char) + 2) elif char == ":": # non-capturing group group = None elif char == "#": # comment while True: if source.next is None: raise source.error("missing ), unterminated comment", source.tell() - start) if sourceget() == ")": break continue elif char in "=!<": # lookahead assertions dir = 1 if char == "<": char = sourceget() if char is None: raise source.error("unexpected end of pattern") if char not in "=!": raise source.error("unknown extension ?<" + char, len(char) + 2) dir = -1 # lookbehind lookbehindgroups = state.lookbehindgroups if lookbehindgroups is None: state.lookbehindgroups = state.groups p = _parse_sub(source, state, verbose, nested + 1) if dir < 0: if lookbehindgroups is None: state.lookbehindgroups = None if not sourcematch(")"): raise source.error("missing ), unterminated subpattern", source.tell() - start) if char == "=": subpatternappend((ASSERT, (dir, p))) else: subpatternappend((ASSERT_NOT, (dir, p))) continue elif char == "(": # conditional backreference group condname = source.getuntil(")") group = None if condname.isidentifier(): condgroup = state.groupdict.get(condname) if condgroup is None: msg = "unknown group name %r" % condname raise source.error(msg, len(condname) + 1) else: try: condgroup = int(condname) if condgroup < 0: raise ValueError except ValueError: msg = "bad character in group name %r" % condname raise source.error(msg, len(condname) + 1) from None if not condgroup: raise source.error("bad group number", len(condname) + 1) if condgroup >= MAXGROUPS: msg = "invalid group reference %d" % condgroup raise source.error(msg, len(condname) + 1) state.checklookbehindgroup(condgroup, source) elif char in FLAGS or char == "-": # flags flags = _parse_flags(source, state, char) if flags is None: # global flags if not first or subpattern: import warnings warnings.warn( 'Flags not at the start of the expression %r%s' % ( source.string[:20], # truncate long regexes ' (truncated)' if len(source.string) > 20 else '', ), DeprecationWarning, stacklevel=nested + 6 ) if (state.flags & SRE_FLAG_VERBOSE) and not verbose: raise Verbose continue add_flags, del_flags = flags group = None else: raise source.error("unknown extension ?" + char, len(char) + 1) # parse group contents if group is not None: try: group = state.opengroup(name) except error as err: raise source.error(err.msg, len(name) + 1) from None if condgroup: p = _parse_sub_cond(source, state, condgroup, verbose, nested + 1) else: sub_verbose = ((verbose or (add_flags & SRE_FLAG_VERBOSE)) and not (del_flags & SRE_FLAG_VERBOSE)) p = _parse_sub(source, state, sub_verbose, nested + 1) if not source.match(")"): raise source.error("missing ), unterminated subpattern", source.tell() - start) if group is not None: state.closegroup(group, p) subpatternappend((SUBPATTERN, (group, add_flags, del_flags, p))) elif this == "^": subpatternappend((AT, AT_BEGINNING)) elif this == "$": subpattern.append((AT, AT_END)) else: raise AssertionError("unsupported special character %r" % (char,)) return subpattern def _parse_flags(source, state, char): sourceget = source.get add_flags = 0 del_flags = 0 if char != "-": while True: add_flags |= FLAGS[char] char = sourceget() if char is None: raise source.error("missing -, : or )") if char in ")-:": break if char not in FLAGS: msg = "unknown flag" if char.isalpha() else "missing -, : or )" raise source.error(msg, len(char)) if char == ")": state.flags |= add_flags return None if add_flags & GLOBAL_FLAGS: raise source.error("bad inline flags: cannot turn on global flag", 1) if char == "-": char = sourceget() if char is None: raise source.error("missing flag") if char not in FLAGS: msg = "unknown flag" if char.isalpha() else "missing flag" raise source.error(msg, len(char)) while True: del_flags |= FLAGS[char] char = sourceget() if char is None: raise source.error("missing :") if char == ":": break if char not in FLAGS: msg = "unknown flag" if char.isalpha() else "missing :" raise source.error(msg, len(char)) assert char == ":" if del_flags & GLOBAL_FLAGS: raise source.error("bad inline flags: cannot turn off global flag", 1) if add_flags & del_flags: raise source.error("bad inline flags: flag turned on and off", 1) return add_flags, del_flags def fix_flags(src, flags): # Check and fix flags according to the type of pattern (str or bytes) if isinstance(src, str): if flags & SRE_FLAG_LOCALE: raise ValueError("cannot use LOCALE flag with a str pattern") if not flags & SRE_FLAG_ASCII: flags |= SRE_FLAG_UNICODE elif flags & SRE_FLAG_UNICODE: raise ValueError("ASCII and UNICODE flags are incompatible") else: if flags & SRE_FLAG_UNICODE: raise ValueError("cannot use UNICODE flag with a bytes pattern") if flags & SRE_FLAG_LOCALE and flags & SRE_FLAG_ASCII: raise ValueError("ASCII and LOCALE flags are incompatible") return flags def parse(str, flags=0, pattern=None): # parse 're' pattern into list of (opcode, argument) tuples source = Tokenizer(str) if pattern is None: pattern = Pattern() pattern.flags = flags pattern.str = str try: p = _parse_sub(source, pattern, flags & SRE_FLAG_VERBOSE, 0) except Verbose: # the VERBOSE flag was switched on inside the pattern. to be # on the safe side, we'll parse the whole thing again... pattern = Pattern() pattern.flags = flags | SRE_FLAG_VERBOSE pattern.str = str source.seek(0) p = _parse_sub(source, pattern, True, 0) p.pattern.flags = fix_flags(str, p.pattern.flags) if source.next is not None: assert source.next == ")" raise source.error("unbalanced parenthesis") if flags & SRE_FLAG_DEBUG: p.dump() return p def parse_template(source, pattern): # parse 're' replacement string into list of literals and # group references s = Tokenizer(source) sget = s.get groups = [] literals = [] literal = [] lappend = literal.append def addgroup(index, pos): if index > pattern.groups: raise s.error("invalid group reference %d" % index, pos) if literal: literals.append(''.join(literal)) del literal[:] groups.append((len(literals), index)) literals.append(None) groupindex = pattern.groupindex while True: this = sget() if this is None: break # end of replacement string if this[0] == "\\": # group c = this[1] if c == "g": name = "" if not s.match("<"): raise s.error("missing <") name = s.getuntil(">") if name.isidentifier(): try: index = groupindex[name] except KeyError: raise IndexError("unknown group name %r" % name) else: try: index = int(name) if index < 0: raise ValueError except ValueError: raise s.error("bad character in group name %r" % name, len(name) + 1) from None if index >= MAXGROUPS: raise s.error("invalid group reference %d" % index, len(name) + 1) addgroup(index, len(name) + 1) elif c == "0": if s.next in OCTDIGITS: this += sget() if s.next in OCTDIGITS: this += sget() lappend(chr(int(this[1:], 8) & 0xff)) elif c in DIGITS: isoctal = False if s.next in DIGITS: this += sget() if (c in OCTDIGITS and this[2] in OCTDIGITS and s.next in OCTDIGITS): this += sget() isoctal = True c = int(this[1:], 8) if c > 0o377: raise s.error('octal escape value %s outside of ' 'range 0-0o377' % this, len(this)) lappend(chr(c)) if not isoctal: addgroup(int(this[1:]), len(this) - 1) else: try: this = chr(ESCAPES[this][1]) except KeyError: if c in ASCIILETTERS: import warnings warnings.warn('bad escape %s' % this, DeprecationWarning, stacklevel=4) lappend(this) else: lappend(this) if literal: literals.append(''.join(literal)) if not isinstance(source, str): # The tokenizer implicitly decodes bytes objects as latin-1, we must # therefore re-encode the final representation. literals = [None if s is None else s.encode('latin-1') for s in literals] return groups, literals def expand_template(template, match): g = match.group empty = match.string[:0] groups, literals = template literals = literals[:] try: for index, group in groups: literals[index] = g(group) or empty except IndexError: raise error("invalid group reference %d" % index) return empty.join(literals)