python文法左递归消除 python实现文法左递归的消除方法

import os
import tkinter as tk
import tkinter.messagebox
import tkinter.font as tf

zhuizhong = ""
wenfa = {"非左递归文法"}
xi_ = ""
huo = ""

window = tk.Tk()
window.title('消除左递归')
window.minsize(500,500)
#转换坐标显示形式为元组
def getIndex(text, pos):
  return tuple(map(int, str.split(text.index(pos), ".")))

def zhijie(x,y):
  if not len(y):
    pass
  else:
    if x == y[0]:
      wenfa.discard("非左递归文法")
      #处理直接左递归
      zuobian = y.split('|')
      feizhongjie = []
      zhongjie = []
      for item in zuobian:
        if x in item:
          item = item[1:]
          textt = str(item) + str(x) + "'"
          feizhongjie.append(textt)
        else:
          text = str(item) + str(x) + "'"
          zhongjie.append(text)
      if not zhongjie:#处理A -> Ax的情况
        zhongjie.append(str(x + "'"))
      cheng = str(x) + " -> " + "|".join(zhongjie)
      zi = str(x) + "'" + " -> " + "|".join(feizhongjie) + "|є"
      text_output.insert('insert','直接左递归文法','tag1')
      text_output.insert('insert','\n')
      text_output.insert('insert',cheng,'tag2')
      text_output.insert('insert','\n')
      text_output.insert('insert',zi,'tag2')
    '''
    加上会判断输出非递归产生式，但会导致间接左递归不能删除多余产生式
    else:
      h ="不变： " + x + " -> " + y
      text_output.insert('insert','非左递归文法','tag1')
      text_output.insert('insert','\n')
      text_output.insert('insert',h,'tag2')
    '''
    text_output.insert('insert','\n')

def zhijie2(x,y):
  if not len(y):
    pass
  else:
    if x == y[0]:
      wenfa.discard("非左递归文法")
      #处理直接左递归
      zuobian = y.split('|')
      feizhongjie = []
      zhongjie = []
      for item in zuobian:
        if x in item:
          item = item[1:]
          textt = str(item) + str(x) + "'"
          feizhongjie.append(textt)
        else:
          text = str(item) + str(x) + "'" 
          zhongjie.append(text)
      cheng = str(x) + " -> " + "|".join(zhongjie)
      zi = str(x) + "'" + " -> " + "|".join(feizhongjie) + "|є"
      text_output.insert('insert',"间接左递归文法",'tag1')
      text_output.insert('insert','\n')
      text_output.insert('insert',cheng,'tag2')
      text_output.insert('insert','\n')
      text_output.insert('insert',zi,'tag2')

    text_output.insert('insert','\n')

def tihuan(xk,yi,yk):
  yi_you = []
  yi_wu =[]
  yi_he = ""
  yi_wuhe = ""
  yi_zhong = ""
  yi_feizhong = []
  if xk in yi:
    yk_replace = yk.split('|')
    yi_fenjie = yi.split('|')#将含非终结与不含分开
    for ba in yi_fenjie:
      if xk in ba:
        yi_you.append(ba)
      else:
        yi_wu.append(ba)

    yi_he = "|".join(yi_you)

    for item in yk_replace:
      yi_zhong = yi_he.replace(xk,item)#替换
      yi_feizhong.append(yi_zhong)
    yi_wuhe = "|".join(yi_wu)#再合并
    global zhuizhong
    zhuizhong = "|".join(yi_feizhong) + "|" + yi_wuhe

#点击按钮后执行的函数
def changeString():
  text_output.delete('1.0','end')
  text = text_input.get('1.0','end')
  text_list = list(text.split('\n'))#一行一行的拿文法
  text_list.pop()
  if not text_list[0]:
    print(tkinter.messagebox.showerror(title = '出错了！',message='输入不能为空'))
  else:
    for cfg in text_list:
      
      x,y = cfg.split('->')#将文法左右分开
      x = ''.join(x.split())#消除空格
      y = ''.join(y.split())
      if not (len(x) == 1 and x >= 'A' and x <= 'Z'):
        pos = text_input.search(x, '1.0', stopindex="end")
        result = tkinter.messagebox.showerror(title = '出错了！',
        message='非上下文无关文法!坐标%s'%(getIndex(text_input, pos),))
        # 返回值为：ok
        print(result)
        return 0
      else:
        zhijie(x,y)
      
    for i in range(len(text_list)):
      for k in range(i):
        xi,yi = text_list[i].split('->')
        xi = ''.join(xi.split())#消除空格
        yi = ''.join(yi.split())
        
        xk,yk = text_list[k].split('->')
        xk = ''.join(xk.split())#消除空格
        yk = ''.join(yk.split())

        tihuan(xk,yi,yk)
        tihuan(xk,zhuizhong,yk)
        global xi_
        xi_ = xi
    zhijie2(xi_,zhuizhong)

    for item in wenfa:
      text_output.insert('insert',item,'tag1')  

    
#创建文本输入框和按钮
text_input = tk.Text(window, width=80, height=16)
text_output = tk.Text(window, width=80, height=20)
#简单样式
ft = tf.Font(family='微软雅黑',size=12)
text_output.tag_config("tag1",background="yellow",foreground="red",font=ft)
text_output.tag_config('tag2',font = ft)
#按钮
button = tk.Button(window,text="消除左递归",command=changeString,padx=32,pady=4,bd=4)
 
text_input.pack()
text_output.pack()
button.pack()
window.mainloop()