Lib/tokenize.py

"""Tokenization help for Python programs.

tokenize(readline) is a generator that breaks a stream of bytes into
Python tokens.  It decodes the bytes according to PEP-0263 for
determining source file encoding.

It accepts a readline-like method which is called repeatedly to get the
next line of input (or b"" for EOF).  It generates 5-tuples with these
members:

    the token type (see token.py)
    the token (a string)
    the starting (row, column) indices of the token (a 2-tuple of ints)
    the ending (row, column) indices of the token (a 2-tuple of ints)
    the original line (string)

It is designed to match the working of the Python tokenizer exactly, except
that it produces COMMENT tokens for comments and gives type OP for all
operators.  Additionally, all token lists start with an ENCODING token
which tells you which encoding was used to decode the bytes stream.
"""

__author__ = 'Ka-Ping Yee <ping@lfw.org>'
__credits__ = ('GvR, ESR, Tim Peters, Thomas Wouters, Fred Drake, '
               'Skip Montanaro, Raymond Hettinger, Trent Nelson, '
               'Michael Foord')
from builtins import open as _builtin_open
from codecs import lookup, BOM_UTF8
import collections
from io import TextIOWrapper
from itertools import chain
import re
import sys
from token import *

cookie_re = re.compile(r'^[ \t\f]*#.*coding[:=][ \t]*([-\w.]+)', re.ASCII)
blank_re = re.compile(br'^[ \t\f]*(?:[#\r\n]|$)', re.ASCII)

import token
__all__ = token.__all__ + ["COMMENT", "tokenize", "detect_encoding",
                           "NL", "untokenize", "ENCODING", "TokenInfo"]
del token

COMMENT = N_TOKENS
tok_name[COMMENT] = 'COMMENT'
NL = N_TOKENS + 1
tok_name[NL] = 'NL'
ENCODING = N_TOKENS + 2
tok_name[ENCODING] = 'ENCODING'
N_TOKENS += 3
EXACT_TOKEN_TYPES = {
    '(':   LPAR,
    ')':   RPAR,
    '[':   LSQB,
    ']':   RSQB,
    ':':   COLON,
    ',':   COMMA,
    ';':   SEMI,
    '+':   PLUS,
    '-':   MINUS,
    '*':   STAR,
    '/':   SLASH,
    '|':   VBAR,
    '&':   AMPER,
    '<':   LESS,
    '>':   GREATER,
    '=':   EQUAL,
    '.':   DOT,
    '%':   PERCENT,
    '{':   LBRACE,
    '}':   RBRACE,
    '==':  EQEQUAL,
    '!=':  NOTEQUAL,
    '<=':  LESSEQUAL,
    '>=':  GREATEREQUAL,
    '~':   TILDE,
    '^':   CIRCUMFLEX,
    '<<':  LEFTSHIFT,
    '>>':  RIGHTSHIFT,
    '**':  DOUBLESTAR,
    '+=':  PLUSEQUAL,
    '-=':  MINEQUAL,
    '*=':  STAREQUAL,
    '/=':  SLASHEQUAL,
    '%=':  PERCENTEQUAL,
    '&=':  AMPEREQUAL,
    '|=':  VBAREQUAL,
    '^=': CIRCUMFLEXEQUAL,
    '<<=': LEFTSHIFTEQUAL,
    '>>=': RIGHTSHIFTEQUAL,
    '**=': DOUBLESTAREQUAL,
    '//':  DOUBLESLASH,
    '//=': DOUBLESLASHEQUAL,
    '@':   AT,
    '@=':  ATEQUAL,
}

class TokenInfo(collections.namedtuple('TokenInfo', 'type string start end line')):
    def __repr__(self):
        annotated_type = '%d (%s)' % (self.type, tok_name[self.type])
        return ('TokenInfo(type=%s, string=%r, start=%r, end=%r, line=%r)' %
                self._replace(type=annotated_type))

    @property
    def exact_type(self):
        if self.type == OP and self.string in EXACT_TOKEN_TYPES:
            return EXACT_TOKEN_TYPES[self.string]
        else:
            return self.type

def group(*choices): return '(' + '|'.join(choices) + ')'
def any(*choices): return group(*choices) + '*'
def maybe(*choices): return group(*choices) + '?'

# Note: we use unicode matching for names ("\w") but ascii matching for
# number literals.
Whitespace = r'[ \f\t]*'
Comment = r'#[^\r\n]*'
Ignore = Whitespace + any(r'\\\r?\n' + Whitespace) + maybe(Comment)
Name = r'\w+'

Hexnumber = r'0[xX][0-9a-fA-F]+'
Binnumber = r'0[bB][01]+'
Octnumber = r'0[oO][0-7]+'
Decnumber = r'(?:0+|[1-9][0-9]*)'
Intnumber = group(Hexnumber, Binnumber, Octnumber, Decnumber)
Exponent = r'[eE][-+]?[0-9]+'
Pointfloat = group(r'[0-9]+\.[0-9]*', r'\.[0-9]+') + maybe(Exponent)
Expfloat = r'[0-9]+' + Exponent
Floatnumber = group(Pointfloat, Expfloat)
Imagnumber = group(r'[0-9]+[jJ]', Floatnumber + r'[jJ]')
Number = group(Imagnumber, Floatnumber, Intnumber)

StringPrefix = r'(?:[bB][rR]?|[rR][bB]?|[uU])?'

# Tail end of ' string.
Single = r"[^'\\]*(?:\\.[^'\\]*)*'"
# Tail end of " string.
Double = r'[^"\\]*(?:\\.[^"\\]*)*"'
# Tail end of ''' string.
Single3 = r"[^'\\]*(?:(?:\\.|'(?!''))[^'\\]*)*'''"
# Tail end of """ string.
Double3 = r'[^"\\]*(?:(?:\\.|"(?!""))[^"\\]*)*"""'
Triple = group(StringPrefix + "'''", StringPrefix + '"""')
# Single-line ' or " string.
String = group(StringPrefix + r"'[^\n'\\]*(?:\\.[^\n'\\]*)*'",
               StringPrefix + r'"[^\n"\\]*(?:\\.[^\n"\\]*)*"')

# Because of leftmost-then-longest match semantics, be sure to put the
# longest operators first (e.g., if = came before ==, == would get
# recognized as two instances of =).
Operator = group(r"\*\*=?", r">>=?", r"<<=?", r"!=",
                 r"//=?", r"->",
                 r"[+\-*/%&@|^=<>]=?",
                 r"~")

Bracket = '[][(){}]'
Special = group(r'\r?\n', r'\.\.\.', r'[:;.,@]')
Funny = group(Operator, Bracket, Special)

PlainToken = group(Number, Funny, String, Name)
Token = Ignore + PlainToken

# First (or only) line of ' or " string.
ContStr = group(StringPrefix + r"'[^\n'\\]*(?:\\.[^\n'\\]*)*" +
                group("'", r'\\\r?\n'),
                StringPrefix + r'"[^\n"\\]*(?:\\.[^\n"\\]*)*' +
                group('"', r'\\\r?\n'))
PseudoExtras = group(r'\\\r?\n|\Z', Comment, Triple)
PseudoToken = Whitespace + group(PseudoExtras, Number, Funny, ContStr, Name)

def _compile(expr):
    return re.compile(expr, re.UNICODE)

endpats = {"'": Single, '"': Double,
           "'''": Single3, '"""': Double3,
           "r'''": Single3, 'r"""': Double3,
           "b'''": Single3, 'b"""': Double3,
           "R'''": Single3, 'R"""': Double3,
           "B'''": Single3, 'B"""': Double3,
           "br'''": Single3, 'br"""': Double3,
           "bR'''": Single3, 'bR"""': Double3,
           "Br'''": Single3, 'Br"""': Double3,
           "BR'''": Single3, 'BR"""': Double3,
           "rb'''": Single3, 'rb"""': Double3,
           "Rb'''": Single3, 'Rb"""': Double3,
           "rB'''": Single3, 'rB"""': Double3,
           "RB'''": Single3, 'RB"""': Double3,
           "u'''": Single3, 'u"""': Double3,
           "U'''": Single3, 'U"""': Double3,
           'r': None, 'R': None, 'b': None, 'B': None,
           'u': None, 'U': None}

triple_quoted = {}
for t in ("'''", '"""',
          "r'''", 'r"""', "R'''", 'R"""',
          "b'''", 'b"""', "B'''", 'B"""',
          "br'''", 'br"""', "Br'''", 'Br"""',
          "bR'''", 'bR"""', "BR'''", 'BR"""',
          "rb'''", 'rb"""', "rB'''", 'rB"""',
          "Rb'''", 'Rb"""', "RB'''", 'RB"""',
          "u'''", 'u"""', "U'''", 'U"""',
          ):
    triple_quoted[t] = t
single_quoted = {}
for t in ("'", '"',
          "r'", 'r"', "R'", 'R"',
          "b'", 'b"', "B'", 'B"',
          "br'", 'br"', "Br'", 'Br"',
          "bR'", 'bR"', "BR'", 'BR"' ,
          "rb'", 'rb"', "rB'", 'rB"',
          "Rb'", 'Rb"', "RB'", 'RB"' ,
          "u'", 'u"', "U'", 'U"',
          ):
    single_quoted[t] = t

tabsize = 8

class TokenError(Exception): pass

class StopTokenizing(Exception): pass


class Untokenizer:

    def __init__(self):
        self.tokens = []
        self.prev_row = 1
        self.prev_col = 0
        self.encoding = None

    def add_whitespace(self, start):
        row, col = start
        if row < self.prev_row or row == self.prev_row and col < self.prev_col:
            raise ValueError("start ({},{}) precedes previous end ({},{})"
                             .format(row, col, self.prev_row, self.prev_col))
        row_offset = row - self.prev_row
        if row_offset:
            self.tokens.append("\\\n" * row_offset)
            self.prev_col = 0
        col_offset = col - self.prev_col
        if col_offset:
            self.tokens.append(" " * col_offset)

    def untokenize(self, iterable):
        it = iter(iterable)
        for t in it:
            if len(t) == 2:
                self.compat(t, it)
                break
            tok_type, token, start, end, line = t
            if tok_type == ENCODING:
                self.encoding = token
                continue
            if tok_type == ENDMARKER:
                break
            self.add_whitespace(start)
            self.tokens.append(token)
            self.prev_row, self.prev_col = end
            if tok_type in (NEWLINE, NL):
                self.prev_row += 1
                self.prev_col = 0
        return "".join(self.tokens)

    def compat(self, token, iterable):
        indents = []
        toks_append = self.tokens.append
        startline = token[0] in (NEWLINE, NL)
        prevstring = False

        for tok in chain([token], iterable):
            toknum, tokval = tok[:2]
            if toknum == ENCODING:
                self.encoding = tokval
                continue

            if toknum in (NAME, NUMBER, ASYNC, AWAIT):
                tokval += ' '

            # Insert a space between two consecutive strings
            if toknum == STRING:
                if prevstring:
                    tokval = ' ' + tokval
                prevstring = True
            else:
                prevstring = False

            if toknum == INDENT:
                indents.append(tokval)
                continue
            elif toknum == DEDENT:
                indents.pop()
                continue
            elif toknum in (NEWLINE, NL):
                startline = True
            elif startline and indents:
                toks_append(indents[-1])
                startline = False
            toks_append(tokval)


def untokenize(iterable):
    """Transform tokens back into Python source code.
    It returns a bytes object, encoded using the ENCODING
    token, which is the first token sequence output by tokenize.

    Each element returned by the iterable must be a token sequence
    with at least two elements, a token number and token value.  If
    only two tokens are passed, the resulting output is poor.

    Round-trip invariant for full input:
        Untokenized source will match input source exactly

    Round-trip invariant for limited intput:
        # Output bytes will tokenize the back to the input
        t1 = [tok[:2] for tok in tokenize(f.readline)]
        newcode = untokenize(t1)
        readline = BytesIO(newcode).readline
        t2 = [tok[:2] for tok in tokenize(readline)]
        assert t1 == t2
    """
    ut = Untokenizer()
    out = ut.untokenize(iterable)
    if ut.encoding is not None:
        out = out.encode(ut.encoding)
    return out


def _get_normal_name(orig_enc):
    """Imitates get_normal_name in tokenizer.c."""
    # Only care about the first 12 characters.
    enc = orig_enc[:12].lower().replace("_", "-")
    if enc == "utf-8" or enc.startswith("utf-8-"):
        return "utf-8"
    if enc in ("latin-1", "iso-8859-1", "iso-latin-1") or \
       enc.startswith(("latin-1-", "iso-8859-1-", "iso-latin-1-")):
        return "iso-8859-1"
    return orig_enc

def detect_encoding(readline):
    """
    The detect_encoding() function is used to detect the encoding that should
    be used to decode a Python source file.  It requires one argument, readline,
    in the same way as the tokenize() generator.

    It will call readline a maximum of twice, and return the encoding used
    (as a string) and a list of any lines (left as bytes) it has read in.

    It detects the encoding from the presence of a utf-8 bom or an encoding
    cookie as specified in pep-0263.  If both a bom and a cookie are present,
    but disagree, a SyntaxError will be raised.  If the encoding cookie is an
    invalid charset, raise a SyntaxError.  Note that if a utf-8 bom is found,
    'utf-8-sig' is returned.

    If no encoding is specified, then the default of 'utf-8' will be returned.
    """
    try:
        filename = readline.__self__.name
    except AttributeError:
        filename = None
    bom_found = False
    encoding = None
    default = 'utf-8'
    def read_or_stop():
        try:
            return readline()
        except StopIteration:
            return b''

    def find_cookie(line):
        try:
            # Decode as UTF-8. Either the line is an encoding declaration,
            # in which case it should be pure ASCII, or it must be UTF-8
            # per default encoding.
            line_string = line.decode('utf-8')
        except UnicodeDecodeError:
            msg = "invalid or missing encoding declaration"
            if filename is not None:
                msg = '{} for {!r}'.format(msg, filename)
            raise SyntaxError(msg)

        match = cookie_re.match(line_string)
        if not match:
            return None
        encoding = _get_normal_name(match.group(1))
        try:
            codec = lookup(encoding)
        except LookupError:
            # This behaviour mimics the Python interpreter
            if filename is None:
                msg = "unknown encoding: " + encoding
            else:
                msg = "unknown encoding for {!r}: {}".format(filename,
                        encoding)
            raise SyntaxError(msg)

        if bom_found:
            if encoding != 'utf-8':
                # This behaviour mimics the Python interpreter
                if filename is None:
                    msg = 'encoding problem: utf-8'
                else:
                    msg = 'encoding problem for {!r}: utf-8'.format(filename)
                raise SyntaxError(msg)
            encoding += '-sig'
        return encoding

    first = read_or_stop()
    if first.startswith(BOM_UTF8):
        bom_found = True
        first = first[3:]
        default = 'utf-8-sig'
    if not first:
        return default, []

    encoding = find_cookie(first)
    if encoding:
        return encoding, [first]
    if not blank_re.match(first):
        return default, [first]

    second = read_or_stop()
    if not second:
        return default, [first]

    encoding = find_cookie(second)
    if encoding:
        return encoding, [first, second]

    return default, [first, second]


def open(filename):
    """Open a file in read only mode using the encoding detected by
    detect_encoding().
    """
    buffer = _builtin_open(filename, 'rb')
    try:
        encoding, lines = detect_encoding(buffer.readline)
        buffer.seek(0)
        text = TextIOWrapper(buffer, encoding, line_buffering=True)
        text.mode = 'r'
        return text
    except:
        buffer.close()
        raise


def tokenize(readline):
    """
    The tokenize() generator requires one argment, readline, which
    must be a callable object which provides the same interface as the
    readline() method of built-in file objects.  Each call to the function
    should return one line of input as bytes.  Alternately, readline
    can be a callable function terminating with StopIteration:
        readline = open(myfile, 'rb').__next__  # Example of alternate readline

    The generator produces 5-tuples with these members: the token type; the
    token string; a 2-tuple (srow, scol) of ints specifying the row and
    column where the token begins in the source; a 2-tuple (erow, ecol) of
    ints specifying the row and column where the token ends in the source;
    and the line on which the token was found.  The line passed is the
    logical line; continuation lines are included.

    The first token sequence will always be an ENCODING token
    which tells you which encoding was used to decode the bytes stream.
    """
    # This import is here to avoid problems when the itertools module is not
    # built yet and tokenize is imported.
    from itertools import chain, repeat
    encoding, consumed = detect_encoding(readline)
    rl_gen = iter(readline, b"")
    empty = repeat(b"")
    return _tokenize(chain(consumed, rl_gen, empty).__next__, encoding)


def _tokenize(readline, encoding):
    lnum = parenlev = continued = 0
    numchars = '0123456789'
    contstr, needcont = '', 0
    contline = None
    indents = [0]

    # 'stashed' and 'ctx' are used for async/await parsing
    stashed = None
    ctx = [('sync', 0)]

    if encoding is not None:
        if encoding == "utf-8-sig":
            # BOM will already have been stripped.
            encoding = "utf-8"
        yield TokenInfo(ENCODING, encoding, (0, 0), (0, 0), '')
    while True:             # loop over lines in stream
        try:
            line = readline()
        except StopIteration:
            line = b''

        if encoding is not None:
            line = line.decode(encoding)
        lnum += 1
        pos, max = 0, len(line)

        if contstr:                            # continued string
            if not line:
                raise TokenError("EOF in multi-line string", strstart)
            endmatch = endprog.match(line)
            if endmatch:
                pos = end = endmatch.end(0)
                yield TokenInfo(STRING, contstr + line[:end],
                       strstart, (lnum, end), contline + line)
                contstr, needcont = '', 0
                contline = None
            elif needcont and line[-2:] != '\\\n' and line[-3:] != '\\\r\n':
                yield TokenInfo(ERRORTOKEN, contstr + line,
                           strstart, (lnum, len(line)), contline)
                contstr = ''
                contline = None
                continue
            else:
                contstr = contstr + line
                contline = contline + line
                continue

        elif parenlev == 0 and not continued:  # new statement
            if not line: break
            column = 0
            while pos < max:                   # measure leading whitespace
                if line[pos] == ' ':
                    column += 1
                elif line[pos] == '\t':
                    column = (column//tabsize + 1)*tabsize
                elif line[pos] == '\f':
                    column = 0
                else:
                    break
                pos += 1
            if pos == max:
                break

            if line[pos] in '#\r\n':           # skip comments or blank lines
                if line[pos] == '#':
                    comment_token = line[pos:].rstrip('\r\n')
                    nl_pos = pos + len(comment_token)
                    yield TokenInfo(COMMENT, comment_token,
                           (lnum, pos), (lnum, pos + len(comment_token)), line)
                    yield TokenInfo(NL, line[nl_pos:],
                           (lnum, nl_pos), (lnum, len(line)), line)
                else:
                    yield TokenInfo((NL, COMMENT)[line[pos] == '#'], line[pos:],
                           (lnum, pos), (lnum, len(line)), line)
                continue

            if column > indents[-1]:           # count indents or dedents
                indents.append(column)
                yield TokenInfo(INDENT, line[:pos], (lnum, 0), (lnum, pos), line)
            while column < indents[-1]:
                if column not in indents:
                    raise IndentationError(
                        "unindent does not match any outer indentation level",
                        ("<tokenize>", lnum, pos, line))
                indents = indents[:-1]

                cur_indent = indents[-1]
                while len(ctx) > 1 and ctx[-1][1] >= cur_indent:
                    ctx.pop()

                yield TokenInfo(DEDENT, '', (lnum, pos), (lnum, pos), line)

        else:                                  # continued statement
            if not line:
                raise TokenError("EOF in multi-line statement", (lnum, 0))
            continued = 0

        while pos < max:
            pseudomatch = _compile(PseudoToken).match(line, pos)
            if pseudomatch:                                # scan for tokens
                start, end = pseudomatch.span(1)
                spos, epos, pos = (lnum, start), (lnum, end), end
                if start == end:
                    continue
                token, initial = line[start:end], line[start]

                if (initial in numchars or                  # ordinary number
                    (initial == '.' and token != '.' and token != '...')):
                    yield TokenInfo(NUMBER, token, spos, epos, line)
                elif initial in '\r\n':
                    if stashed:
                        yield stashed
                        stashed = None
                    yield TokenInfo(NL if parenlev > 0 else NEWLINE,
                           token, spos, epos, line)
                elif initial == '#':
                    assert not token.endswith("\n")
                    if stashed:
                        yield stashed
                        stashed = None
                    yield TokenInfo(COMMENT, token, spos, epos, line)
                elif token in triple_quoted:
                    endprog = _compile(endpats[token])
                    endmatch = endprog.match(line, pos)
                    if endmatch:                           # all on one line
                        pos = endmatch.end(0)
                        token = line[start:pos]
                        yield TokenInfo(STRING, token, spos, (lnum, pos), line)
                    else:
                        strstart = (lnum, start)           # multiple lines
                        contstr = line[start:]
                        contline = line
                        break
                elif initial in single_quoted or \
                    token[:2] in single_quoted or \
                    token[:3] in single_quoted:
                    if token[-1] == '\n':                  # continued string
                        strstart = (lnum, start)
                        endprog = _compile(endpats[initial] or
                                           endpats[token[1]] or
                                           endpats[token[2]])
                        contstr, needcont = line[start:], 1
                        contline = line
                        break
                    else:                                  # ordinary string
                        yield TokenInfo(STRING, token, spos, epos, line)
                elif initial.isidentifier():               # ordinary name
                    if token in ('async', 'await'):
                        if ctx[-1][0] == 'async' and ctx[-1][1] < indents[-1]:
                            yield TokenInfo(
                                ASYNC if token == 'async' else AWAIT,
                                token, spos, epos, line)
                            continue

                    tok = TokenInfo(NAME, token, spos, epos, line)
                    if token == 'async' and not stashed:
                        stashed = tok
                        continue

                    if token == 'def':
                        if (stashed
                                and stashed.type == NAME
                                and stashed.string == 'async'):

                            ctx.append(('async', indents[-1]))

                            yield TokenInfo(ASYNC, stashed.string,
                                            stashed.start, stashed.end,
                                            stashed.line)
                            stashed = None
                        else:
                            ctx.append(('sync', indents[-1]))

                    if stashed:
                        yield stashed
                        stashed = None

                    yield tok
                elif initial == '\\':                      # continued stmt
                    continued = 1
                else:
                    if initial in '([{':
                        parenlev += 1
                    elif initial in ')]}':
                        parenlev -= 1
                    if stashed:
                        yield stashed
                        stashed = None
                    yield TokenInfo(OP, token, spos, epos, line)
            else:
                yield TokenInfo(ERRORTOKEN, line[pos],
                           (lnum, pos), (lnum, pos+1), line)
                pos += 1

    if stashed:
        yield stashed
        stashed = None

    for indent in indents[1:]:                 # pop remaining indent levels
        yield TokenInfo(DEDENT, '', (lnum, 0), (lnum, 0), '')
    yield TokenInfo(ENDMARKER, '', (lnum, 0), (lnum, 0), '')


# An undocumented, backwards compatible, API for all the places in the standard
# library that expect to be able to use tokenize with strings
def generate_tokens(readline):
    return _tokenize(readline, None)

def main():
    import argparse

    # Helper error handling routines
    def perror(message):
        print(message, file=sys.stderr)

    def error(message, filename=None, location=None):
        if location:
            args = (filename,) + location + (message,)
            perror("%s:%d:%d: error: %s" % args)
        elif filename:
            perror("%s: error: %s" % (filename, message))
        else:
            perror("error: %s" % message)
        sys.exit(1)

    # Parse the arguments and options
    parser = argparse.ArgumentParser(prog='python -m tokenize')
    parser.add_argument(dest='filename', nargs='?',
                        metavar='filename.py',
                        help='the file to tokenize; defaults to stdin')
    parser.add_argument('-e', '--exact', dest='exact', action='store_true',
                        help='display token names using the exact type')
    args = parser.parse_args()

    try:
        # Tokenize the input
        if args.filename:
            filename = args.filename
            with _builtin_open(filename, 'rb') as f:
                tokens = list(tokenize(f.readline))
        else:
            filename = "<stdin>"
            tokens = _tokenize(sys.stdin.readline, None)

        # Output the tokenization
        for token in tokens:
            token_type = token.type
            if args.exact:
                token_type = token.exact_type
            token_range = "%d,%d-%d,%d:" % (token.start + token.end)
            print("%-20s%-15s%-15r" %
                  (token_range, tok_name[token_type], token.string))
    except IndentationError as err:
        line, column = err.args[1][1:3]
        error(err.args[0], filename, (line, column))
    except TokenError as err:
        line, column = err.args[1]
        error(err.args[0], filename, (line, column))
    except SyntaxError as err:
        error(err, filename)
    except OSError as err:
        error(err)
    except KeyboardInterrupt:
        print("interrupted\n")
    except Exception as err:
        perror("unexpected error: %s" % err)
        raise

if __name__ == "__main__":
    main()