查看正文内容
from __future__ import print_function
import sys# following two must remain in the same ordertk_EOI, tk_Mul, tk_Div, tk_Mod, tk_Add, tk_Sub, tk_Negate, tk_Not, tk_Lss, tk_Leq, tk_Gtr, \
tk_Geq, tk_Eq, tk_Neq, tk_Assign, tk_And, tk_Or, tk_If, tk_Else, tk_While, tk_Print, \
tk_Putc, tk_Lparen, tk_Rparen, tk_Lbrace, tk_Rbrace, tk_Semi, tk_Comma, tk_Ident, \
tk_Integer, tk_String = range(31)all_syms = ["End_of_input", "Op_multiply", "Op_divide", "Op_mod", "Op_add", "Op_subtract","Op_negate", "Op_not", "Op_less", "Op_lessequal", "Op_greater", "Op_greaterequal","Op_equal", "Op_notequal", "Op_assign", "Op_and", "Op_or", "Keyword_if","Keyword_else", "Keyword_while", "Keyword_print", "Keyword_putc", "LeftParen","RightParen", "LeftBrace", "RightBrace", "Semicolon", "Comma", "Identifier","Integer", "String"]# single character only symbols
symbols = {
'{': tk_Lbrace, '}': tk_Rbrace, '(': tk_Lparen, ')': tk_Rparen, '+': tk_Add, '-': tk_Sub,'*': tk_Mul, '%': tk_Mod, ';': tk_Semi, ',': tk_Comma }key_words = {
'if': tk_If, 'else': tk_Else, 'print': tk_Print, 'putc': tk_Putc, 'while': tk_While}the_ch = " " # dummy first char - but it must be a space
the_col = 0
the_line = 1
input_file = None#*** show error and exit
def error(line, col, msg):print(line, col, msg)exit(1)#*** get the next character from the input
def next_ch():global the_ch, the_col, the_linethe_ch = input_file.read(1)the_col += 1if the_ch == '\n':the_line += 1the_col = 0return the_ch#*** 'x' - character constants
def char_lit(err_line, err_col):n = ord(next_ch()) # skip opening quoteif the_ch == '\'':error(err_line, err_col, "empty character constant")elif the_ch == '\\':next_ch()if the_ch == 'n':n = 10elif the_ch == '\\':n = ord('\\')else:error(err_line, err_col, "unknown escape sequence \\%c" % (the_ch))if next_ch() != '\'':error(err_line, err_col, "multi-character constant")next_ch()return tk_Integer, err_line, err_col, n#*** process divide or comments
def div_or_cmt(err_line, err_col):if next_ch() != '*':return tk_Div, err_line, err_col# comment foundnext_ch()while True:if the_ch == '*':if next_ch() == '/':next_ch()return gettok()elif len(the_ch) == 0:error(err_line, err_col, "EOF in comment")else:next_ch()#*** "string"
def string_lit(start, err_line, err_col):text = ""while next_ch() != start:if len(the_ch) == 0:error(err_line, err_col, "EOF while scanning string literal")if the_ch == '\n':error(err_line, err_col, "EOL while scanning string literal")text += the_chnext_ch()return tk_String, err_line, err_col, text#*** handle identifiers and integers
def ident_or_int(err_line, err_col):is_number = Truetext = ""while the_ch.isalnum() or the_ch == '_':text += the_chif not the_ch.isdigit():is_number = Falsenext_ch()if len(text) == 0:error(err_line, err_col, "ident_or_int: unrecognized character: (%d) '%c'" % (ord(the_ch), the_ch))if text[0].isdigit():if not is_number:error(err_line, err_col, "invalid number: %s" % (text))n = int(text)return tk_Integer, err_line, err_col, nif text in key_words:return key_words[text], err_line, err_colreturn tk_Ident, err_line, err_col, text#*** look ahead for '>=', etc.
def follow(expect, ifyes, ifno, err_line, err_col):if next_ch() == expect:next_ch()return ifyes, err_line, err_colif ifno == tk_EOI:error(err_line, err_col, "follow: unrecognized character: (%d) '%c'" % (ord(the_ch), the_ch))return ifno, err_line, err_col#*** return the next token type
def gettok():while the_ch.isspace():next_ch()err_line = the_lineerr_col = the_colif len(the_ch) == 0: return tk_EOI, err_line, err_colelif the_ch == '/': return div_or_cmt(err_line, err_col)elif the_ch == '\'': return char_lit(err_line, err_col)elif the_ch == '<': return follow('=', tk_Leq, tk_Lss, err_line, err_col)elif the_ch == '>': return follow('=', tk_Geq, tk_Gtr, err_line, err_col)elif the_ch == '=': return follow('=', tk_Eq, tk_Assign, err_line, err_col)elif the_ch == '!': return follow('=', tk_Neq, tk_Not, err_line, err_col)elif the_ch == '&': return follow('&', tk_And, tk_EOI, err_line, err_col)elif the_ch == '|': return follow('|', tk_Or, tk_EOI, err_line, err_col)elif the_ch == '"': return string_lit(the_ch, err_line, err_col)elif the_ch in symbols:sym = symbols[the_ch]next_ch()return sym, err_line, err_colelse: return ident_or_int(err_line, err_col)#*** main driver
input_file = sys.stdin
if len(sys.argv) > 1:try:input_file = open(sys.argv[1], "r", 4096)except IOError as e:error(0, 0, "Can't open %s" % sys.argv[1])while True:t = gettok()tok = t[0]line = t[1]col = t[2]print("%5d %5d %-14s" % (line, col, all_syms[tok]), end='')if tok == tk_Integer: print(" %5d" % (t[3]))elif tok == tk_Ident: print(" %s" % (t[3]))elif tok == tk_String: print(' "%s"' % (t[3]))else: print("")if tok == tk_EOI:break
输出（测试用例三）
5 16 Keyword_print5 40 Op_subtract6 16 Keyword_putc6 40 Op_less7 16 Keyword_if7 40 Op_greater8 16 Keyword_else8 40 Op_lessequal9 16 Keyword_while9 40 Op_greaterequal10 16 LeftBrace10 40 Op_equal11 16 RightBrace11 40 Op_notequal12 16 LeftParen12 40 Op_and13 16 RightParen13 40 Op_or14 16 Op_subtract14 40 Semicolon15 16 Op_not15 40 Comma16 16 Op_multiply16 40 Op_assign17 16 Op_divide17 40 Integer 4218 16 Op_mod18 40 String "String literal"19 16 Op_add19 40 Identifier variable_name20 26 Integer 1021 26 Integer 9222 26 Integer 3223 1 End_of_input