实验三LR1分析报告法实验报告材料三点检验法检验表.docx
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实验三LR1分析报告法实验报告材料三点检验法检验表.docx
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实验三LR1分析报告法实验报告材料三点检验法检验表
实验三LR
(1)分析报告法实验报告材料_三点检验法检验表
一、实验目的构造LR
(1)分析程序,利用它进行语法分析,判断给出的符号串是否为该文法识别的句子,了解LR(K)分析方法是严格的从左向右扫描,和自底向上的语法分析方法。
二、LR
(1)分析法实验设计思想及算法
(1)总控程序,也可以称为驱动程序。
对所有的LR分析器总控程序都是相同的。
(2)分析表或分析函数,不同的文法分析表将不同,同一个文法采用的LR分析器不同时,分析表将不同,分析表又可以分为动作表(ACTION)和状态转换(GOTO)表两个部分,它们都可用二维数组表示。
(3)分析栈,包括文法符号栈和相应的状态栈,它们均是先进后出栈。
分析器的动作就是由栈顶状态和当前输入符号所决定。
LR分析器由三个部分组成:
其中:
SP为栈指针,S[i]为状态栈,X[i]为文法符号栈。
状态转换表用GOTO[i,X]=j表示,规定当栈顶状态为i,遇到当前文法符号为X时应转向状态j,X为终结符或非终结符。
ACTION[i,a]规定了栈顶状态为i时遇到输入符号a应执行。
动作有四种可能:
(1)移进:
action[i,a]=Sj:
状态j移入到状态栈,把a移入到文法符号栈,其中i,j表示状态号。
(2)归约:
action[i,a]=rk:
当在栈顶形成句柄时,则归约为相应的非终结符A,即文法中有A-B的产生式,若B的长度为R(即|B|=R),则从状态栈和文法符号栈中自顶向下去掉R个符号,即栈指针SP减去R,并把A移入文法符号栈,j=GOTO[i,A]移进状态栈,其中i为修改指针后的栈顶状态。
(3)接受acc:
当归约到文法符号栈中只剩文法的开始符号S时,并且输入符号串已结束即当前输入符是'#',则为分析成功。
(4)报错:
当遇到状态栈顶为某一状态下出现不该遇到的文法符号时,则报错,说明输入端不是该文法能接受的符号串。
三、程序结构描述
1、定义的变量
stringaction[12][6]={
{"s5","error","error","s4","error","error"},
{"error","s6","error","error","error","acc"},
{"error","r2","s7","error","r2","r2"},
{"error","r4","r4","error","r4","r4"},
{"s5","error","error","s4","error","error"},
{"error","r6","r6","error","r6","r6"},
{"s5","error","error","s4","error","error"},
{"s5","error","error","s4","error","error"},
{"error","s6","error","error","s11","error"},
{"error","r1","r7","error","r1","r1"},
{"error","r3","r3","error","r3","r3"},
{"error","r5","r5","error","r5","r5"}
};
stringgo[12][3]={
{"1","2","3"},
{"error","error","error"},
{"error","error","error"},
{"error","error","error"},
{"8","2","3"},
{"error","error","error"},
{"error","9","3"},
{"error","error","10"},
{"error","error","error"},
{"error","error","error"},
{"error","error","error"},
{"error","error","error"},
};//初始化预测分析表
charVt[6]={'i','+','*','(',')','#'};终结符表
stringLR[6]={"E->E+T","E->T","T->T*F","T->F","F->(E)","F->i"};//LR文法
stack
stack
charinput[10];输入字符
2、定义的函数
intnum(strings)判断字符串中的数字
voidprint(inti,char*c)剩余输入串的输出
intsame(chara)用于查找终结符
voidanalyse()分析程序
四、程序源代码及运行结果
#include
#include
#include
#include
usingnamespacestd;
//初始化预测分析表
stringaction[12][6]={
{"s5","error","error","s4","error","error"},
{"error","s6","error","error","error","acc"},
{"error","r2","s7","error","r2","r2"},
{"error","r4","r4","error","r4","r4"},
{"s5","error","error","s4","error","error"},
{"error","r6","r6","error","r6","r6"},
{"s5","error","error","s4","error","error"},
{"s5","error","error","s4","error","error"},
{"error","s6","error","error","s11","error"},
{"error","r1","r7","error","r1","r1"},
{"error","r3","r3","error","r3","r3"},
{"error","r5","r5","error","r5","r5"}
};
stringgo[12][3]={
{"1","2","3"},
{"error","error","error"},
{"error","error","error"},
{"error","error","error"},
{"8","2","3"},
{"error","error","error"},
{"error","9","3"},
{"error","error","10"},
{"error","error","error"},
{"error","error","error"},
{"error","error","error"},
{"error","error","error"},
};
charVt[6]={'i','+','*','(',')','#'};//终结符表
stringLR[6]={"E->E+T","E->T","T->T*F","T->F","F->(E)","F->i"};//LR文法
stack
stack
charinput[10];//输入字符
intnum(strings){//判断字符串中的数字
inti;
stringstr="";
for(intj=0;j if(s[j]>='0'&&s[j]<='9')str=str+s[j]; } i=atoi(str.c_str()); returni; } voidprint(inti,char*c)//剩余输入串的输出 { for(intj=i;j<10;j++) cout< cout<<'\t'; } intsame(chara){//用于查找终结符 for(inti=0;i<6;i++){ if(a==Vt[i])returni; } } ///**********分析程序******************* voidanalyse(){ boolflag=true;//循环条件 intstep=1,point=0,state=0;//步骤、指针、状态 charch1,ch2; intm,n,l;//用于判断终结符,分析表,表达式右部的长度 stringstr1;//用于判断对应分析表中的符号 stringstr2="#",str3="0";//记录符号栈的所有元素 cout<<"请输入要规约的字符串: "< cin>>input; X.push('#'); S.push(0); cout<<"步骤"<<'\t'<<"状态栈"<<'\t'<<"符号栈"<<'\t'<<"输入串"<<'\t'<<"动作"< cout< print(point,input); cout<<"初始化"< //************进入循环 while(flag){ state=S.top(); ch1=input[point]; m=same(ch1); str1=action[state][m]; //***********移进动作 if(str1[0]=='s'){ n=num(str1); S.push(n); X.push(ch1); str2=str2+ch1; ch2=n+48; str3=str3+ch2; point++; cout< print(point,input); cout< '<<"移进"< } //**********归约动作 elseif(str1[0]=='r'){ n=num(str1); l=LR[n-1].length()-3; for(inti=1;i<=l;i++){S.pop(); str3=str3.substr(0,str3.length()-1); X.pop(); str2=str2.substr(0,str2.length()-1); } X.push(LR[n-1][0]); str2=str2+LR[n-1][0]; state=S.top(); if(LR[n-1][0]=='E'){S.push(num(go[state][0])); ch2=num(go[state][0])+48; str3=str3+ch2; } elseif(LR[n-1][0]=='T'){S.push(num(go[state][1])); ch2=num(go[state][1])+48; str3=str3+ch2; } elseif(LR[n-1][0]=='F'){S.push(num(go[state][2])); ch2=num(go[state][2])+48; str3=str3+ch2; } cout< print(point,input); cout< '< } //*********出错 elseif(str1=="error"){ cout<<"ERROR"<<"程序错误,分析结束! ! ! "< flag=false; } //**********分析成功 elseif(str1=="acc"){cout<<"分析成功,终止程序"< flag=false; } } } intmain(){ analyse(); return0; } 测试: i*i+i 结果: 五、实验总结
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- 实验 LR1 分析 报告 材料 检验