【发布时间】：2020-05-14 01:20:54
【问题描述】：
你好堆栈溢出用户 我希望你过得很好 所以我正在为我的家庭作业做这个小语言编译器 尝试使用正则表达式 但是输出太奇怪了 首先，我得到一个名为“t”的标识符，它在我的输入中没有使用 它不会将标识符“x”与分号分开 提前感谢您的帮助
这是我的意见
read x; {input an integer }
if 0 < x then { don’t compute if x <= 0 }
fact := 1;
repeat
fact := fact * x;
x := x - 1
until x = 0;
write fact { output factorial of x }
end
这是我使用正则表达式的代码
# -*- coding: utf-8 -*-
"""
Created on Wed May 13 04:11:06 2020
@author: PC
"""
class OwnCompiler (object):
def __init__ (self,file):
import re
self.file=open(file,"r").readlines()
self.symbols = {
"+":"PLUS_OP",
"-":"MINUS_OP",
"*":"MUL_OP",
"/":"DIV_OP",
"=":"EQUAL_OP",
"<":"LESS_OP",
">":"GREATER_OP",
"(":"LEFT_PARENTHESIS",
")":"RIGHT_PARENTHESIS",
":=":"ASSIGN",
";":"SEMICOLON",
}
self.commentPattern = re.compile(r".*({\n*\s*.*\s*})")
self.reservePattern = re.compile(r"\s*(read|write|if|then|else|end|repeat|until)+\s*(.*)(then)*")
self.symbolPattern = re.compile(r".*(\+|\*|-|/|=|<|>|\(|\)|;)")
self.identifierSymbol = re.compile(r".*(\w+)\s+(:=)\s+(.*)")
def compileOutput(self):
self.fileWrite=open("output.txt","w")
self.fileWrite.write("Type Token\n==================\n")
for i in self.file :
print(i)
self.getComment(i)
self.getReserveWord(i)
self.getIdentify(i)
self.fileWrite.close()#end
def getComment(self,text):
try:
self.fileWrite.write("COMMENT "+self.commentPattern.match(text).group(1)+"\n")
except:
print("NO_COMMENT")
def getReserveWord(self,text):
self.Compiled = self.reservePattern.match(text)
try:
self.fileWrite.write("RESERVE_WORD "+self.Compiled.group(1)+"\n")
self.getSymbols(self.Compiled.group(2))
try:
self.fileWrite.write("RESERVE_WORD "+self.Compiled.group(3)+"\n")
except:
print("NO_RESERVE_WORD2")
except:
print("NO_RESERVE_WORD")
def getSymbols(self,text):
self.Compiled= self.symbolPattern.match(text)
self.GOT_TOKEN= self.getTokensSymbols(self.Compiled.group())
try:
self.fileWrite.write(self.GOT_TOKEN+" "+self.Compiled.group()+"\n")
except:
print("NO_SYMBOLS")
def getIdentify(self,text):
self.Compiled = self.identifierSymbol.match(text)
try:
self.fileWrite.write("IDENTIFIER "+self.Compiled.group(1)+"\n")
self.getSymbols(text)
for i in self.Compiled.group(3):
if i ==" " :
continue
if self.isNumber(i):
self.fileWrite.write("NUMBER ")
else:
self.fileWrite.write("WORD ")
self.fileWrite.write(self.Compiled.group(3)+"\n")
except:
print("NO_IDENTIFIRES")
def getTokensSymbols(self,symbol):
try:
return self.symbols[symbol]
except:
print("NOT_DEFINED_IN_SYMBOL_DICT")
return "UNKNOWN"
def isNumber(self,text):
try:
int(text)
return True
except:
return False
if __name__ == "__main__":
instance = OwnCompiler("input.txt")
instance.compileOutput()
这是我的输出
Type Token
==================
COMMENT { Sample program in TINY language – computes factorial }
COMMENT {input an integer }
RESERVE_WORD read
UNKNOWN x;
COMMENT { don’t compute if x <= 0 }
RESERVE_WORD if
UNKNOWN 0 < x then { don’t compute if x <=
IDENTIFIER t
UNKNOWN fact := 1;
RESERVE_WORD repeat
IDENTIFIER t
UNKNOWN fact := fact * x;
IDENTIFIER x
UNKNOWN x := x -
RESERVE_WORD until
UNKNOWN x = 0;
COMMENT { output factorial of x }
RESERVE_WORD write
RESERVE_WORD end
【问题讨论】：
-
当前给出的代码不构成minimal reproducible example——有人不能自己运行它来重现问题或测试修复。顺便说一句，通常我会使用许多可用的解析器生成器之一。通常，
.*不应该在编译器的任何地方使用——记住，它是贪婪的；所以在if(.*)end，如果你有if foo; then bar; end; something-else; if qux; then meh; end，第一个if会一直到你的程序结束，而不是停在它匹配的end实例。 -
对代码部分进行了更新，抱歉它与最小可重现示例不匹配，因为我真的不知道代码有什么问题
标签： python regex compiler-construction