# NeWS parser.
# Don Hopkins


# Data types
#   simple
#     boolean fontID integer mark name null operator real save
#   composite
#     array dictionary file gstate packedarray string
#
# attributes
#   executable bit: literal or executable
#   access bits: unlimited, read-only, execute-only, none
#   attributes are properties of the object (reference) not its value, except for dictionaries
#
# arrays
#   shared sub-structure to support getinterval
#   packed arrays
#
# dictionares
#   can't have null as keys
#
# strings
#   shared sub-structure to support getinterval
#
# two slashes before a name to inline its binding
#
# NeWS supports characters with high bits binding to system and user objects
#
# end of line handling rules, line continuation, cr, lf and cr/lf handling
#
# files
#   %stdin %stdout %statementedit %lineedit %socket
#   r w a r+ w+ a+

def getchar():
    return None

def ungetchar(c):
    pass

def remember(c):
    pass

def iseof(c):
    return c is None

def ishigh(c):
    return ord(c) > 127

def iseol(c):
    return c == '\n'

def iswhite(c):
    return c in '\0\t\n\f\r ' # defined in red book

def isdelim(c):
    return c in '()<>[]{}/%' # defined in red book

def token():
    # Skip spaces and comments.
    while True:

        c = getchar()

        # If comment, then skip until end of line or end of file.
        if c == '%':
            while True:
                c = getchar()
                if (iseol(c) or iseof(c))
                    break

        # If not space or high bit set.
        if ((not isspace(c)) or ishigh(c)):
            break

    if not ishigh(c):
        if ((c == '[') or (c == ']')):
            # array
            # [ and ] are self delimiting name objects that bind to operators, not punctuation
        elif c == '(':
            # parse string
            # literal (string)
            #   parens nest, newlines allowed, \ escapes, \n \r \t \b \f \\ \( \) \ddd (octal character code)
            #   line continuation: \ at end of line ignores \ and newline
            # base-85 <~WXYZ~> (level 2)
        elif c == '<':
            # hex <1234>
            #   if final hex digit is missing, then assume a 0
            # dictionary <<key val key val ...>> (level 2)
            # << and >> are self delimiting name objects that bind to operators, not punctuation
        elif c == '{':
            # begin brace
            # self delimiting
        elif c == '}':
            # end brace
            # self delimiting
        elif c == '/':
            # slash
        else:
            if ishigh(c):
                ungetchar(c)
            else:
                # names may begin with digits as long as they are not numbers
                while True:
                    remember(c)
                    c = getchar()
                    if c <= ' ':
                        break
                    if isdelim(c):
                        ungetchar(c)
                        break
            if memory() <= '9':
                # parse number
                # integer 123 -98 43455 0 +17
                # float -.002 34.5 -3.62 123.6e10 1E-5 -1. 0.0 1E6 1.0E6 1.0E-6
                # radix 8#1777 16#FFFE 2#1000, base is 2-36, digits are 0-9 a-z A-Z