实验二 LL(1)预测分析

1、.实验二 LL(1)分析的设计与实现开课实验室： A201，A207 实验项目LL(1)分析的设计与实现实验类型设计实验学时4一、实验目的根据某一文法编制调试LL(1)分析程序，以便对任意输入的符号串进行分析。掌握LL(1)分析法的基本原理，LL(1)分析表的构造方法，LL(1)驱动程序的构造方法。二、设备与环境 1. 硬件设备：PC机一台2. 软件环境：安装Windows操作系统或者Linux操作系统，并安装相关的程序开发环境，如C C+Java 等编程语言环境。三、实验要求1. 输入文法G的非终结符、终结符和产生式；（1）输出非终结符的FIRST集；（2）输出非终结符的FOLLOW集；（3

2、）构造文法G的预测分析表；（4）对输入符号串进行分析。2、编程语言不限。四、实验原理1.程序功能（流程图参考）：2. 计算FIRST集合：First集合最终是对产生式右部的字符串而言的，但其关键是求出非终结符的First集合，由于终结符的First集合就是它自己，所以求出非终结符的First集合后，就可很直观地得到每个字符串的First集合。 直接收取：对形如Ua的产生式（其中a是终结符），把a收入到First(U)中 反复传送：对形入UP的产生式（其中P是非终结符），应把First(P)中的全部内容传送到First(U)中。算法描述：见教材P80) 若XVt,则FIRST(X)=X;) 若X

3、Vn,且有产生式X-a,aVt，则aFIRST(X);) 若XVn,X-e,则eFIRST(X) 若X,Y1,Y2,Y3,Y4Yn都Vn,而产生式X-Y1,Y2Yn.当Y1,Y2,Y3,Y4Yn都能=e，那么FIRST(X)=并集的FIRST(Yi)- e(0=ie (i=1,2,3)，则FIRST(X)=并集的FIRST(Yi)- e并上e3. 计算FOLLOW集合：Follow集合是针对非终结符而言的，Follow(U)所表达的是句型中非终结符U所有可能的后随终结符号的集合，特别地，“#”是识别符号的后随符。 直接收取：注意产生式右部的每一个形如“Ua”的组合，把a直接收入到Follow(

4、U)中； 直接收取：对形如“UP”(P是非终结符)的组合，把First(P)直接收入到Follow(U)中； 直接收取：若为文法开始符号S，则把#收入FOLLOW(S)； 反复传送：对形如UP的产生式（其中P是非终结符），应把Follow(U)中的全部内容传送到Follow(P)中。算法描述：见教材P82) 若为文法开始符号S，则FOLLOW(S)=# ) 若为文法A-aBb是一个产生式，则把FIRST（b）的非空元素加入 FOLLOW(B)中。如果b-则把FOLLOW(A)也加入FOLLOW(B)中。4. 构造预测分析表：(1) 对于文法的每条产生式Aa，若aFIRST(a)，则MA, a

5、= A a；(2) 若eFIRST(a)，bFOLLOW(a)则MA, b = A a；(3) 分析表M的其他元素均为出错标志error。5. 预测分析程序流图：见课本P93-P94五、程序源码#include stdio.h#include stdlib.h#define MaxRuleNum 8#define MaxVnNum 5#define MaxVtNum 5#define MaxStackDepth 20#define MaxPLength 20#define MaxStLength 50struct pRNode /*产生式右部结构*/ int rCursor; struct p

6、RNode *next;struct pNode int lCursor; int rLength; /*右部长度*/ struct pRNode *rHead; /*右部结点头指针*/;char VnMaxVnNum + 1; /*非终结符集*/int vnNum;char VtMaxVtNum + 1; /*终结符集*/int vtNum;struct pNode PMaxRuleNum; int PNum; char bufferMaxPLength + 1;char ch; char stMaxStLength; /*要分析的符号串*/struct collectNode int nV

7、t; struct collectNode *next;struct collectNode* firstMaxVnNum + 1; /*first集*/struct collectNode* followMaxVnNum + 1; /*follow集*/int analyseTableMaxVnNum + 1MaxVtNum + 1 + 1;int analyseStackMaxStackDepth + 1; /*分析栈*/int topAnalyse; /*分析栈顶*/void Init();/*初始化*/int IndexCh(char ch);void InputVt(); /*输入终

8、结符*/void InputVn();/*输入非终结符*/void ShowChArray(char* collect, int num);/*输出Vn或Vt的内容*/void InputP();/*产生式输入*/bool CheckP(char * st);/*判断产生式正确性*/void First(int U);void AddFirst(int U, int nCh); /*加入first集*/bool HaveEmpty(int nVn); void Follow(int V);/*计算follow集*/void AddFollow(int V, int nCh, int kind)

9、;void ShowCollect(struct collectNode *collect);/*输出first或follow集*/void FirstFollow();/*计算first和follow*/void CreateAT();/*构造预测分析表*/void ShowAT();/*输出分析表*/void Identify(char *st);void InitStack();void ShowStack();void Pop();void Push(int r);void main(void) char todo,ch; Init(); InputVn(); InputVt(); I

10、nputP(); getchar(); FirstFollow(); printf(所得first集为：); ShowCollect(first); printf(所得follow集为：); ShowCollect(follow); CreateAT(); ShowAT(); todo = y; while(y = todo) printf(n是否继续进行句型分析？(y / n):); todo = getchar(); while(y != todo & n != todo) printf(n(y / n)? ); todo = getchar(); if(y = todo) int i;

11、InitStack(); printf(请输入符号串(以#结束) : ); ch = getchar(); i = 0; while(# != ch & i MaxStLength) if( != ch & n != ch) sti+ = ch; ch = getchar(); if(# = ch & i MaxStLength) sti = ch; Identify(st); else printf(输入出错！n); getchar();void Init() int i,j; vnNum = 0; vtNum = 0; PNum = 0; for(i = 0; i = MaxVnNum;

12、i+) Vni = 0; for(i = 0; i = MaxVtNum; i+) Vti = 0; for(i = 0; i MaxRuleNum; i+) Pi.lCursor = NULL; Pi.rHead = NULL; Pi.rLength = 0; PNum = 0; for(i = 0; i = MaxPLength; i+) bufferi = 0; for(i = 0; i MaxVnNum; i+) firsti = NULL; followi = NULL; for(i = 0; i = MaxVnNum; i+) for(j = 0; j = MaxVnNum + 1

13、; j+) analyseTableij = -1; int IndexCh(char ch) int n; n = 0; /*is Vn?*/ while(ch != Vnn & 0 != Vnn) n+; if(0 != Vnn) return 100 + n; n = 0; /*is Vt?*/ while(ch != Vtn & 0 != Vtn) n+; if(0 != Vtn) return n; return -1;/*输出Vn或Vt的内容*/void ShowChArray(char* collect) int k = 0; while(0 != collectk) print

14、f( %c , collectk+); printf(n);/*输入非终结符*/void InputVn() int inErr = 1; int n,k; char ch; while(inErr) printf(n请输入所有的非终结符，注意：); printf(请将开始符放在第一位，并以#号结束:n); ch = ; n = 0; /*初始化数组*/ while(n MaxVnNum) Vnn+ = 0; n = 0; while(# != ch) & (n MaxVnNum) if( != ch & n != ch & -1 = IndexCh(ch) Vnn+ = ch; vnNum+

15、; ch = getchar(); Vnn = #; /*以“#”标志结束用于判断长度是否合法*/ k = n; if(# != ch) if( # != (ch = getchar() while(# != (ch = getchar() ; printf(n符号数目超过限制！n); inErr = 1; continue; /*正确性确认，正确则，执行下下面，否则重新输入*/ Vnk = 0; ShowChArray(Vn); ch = ; while(y != ch & n != ch) if(n != ch) printf(输入正确确认?(y/n):); scanf(%c, &ch);

16、 if(n = ch) printf(录入错误重新输入！n); inErr = 1; else inErr = 0; /*输入终结符*/void InputVt() int inErr = 1; int n,k; char ch; while(inErr) printf(n请输入所有的终结符，注意：); printf(以#号结束:n); ch = ; n = 0; /*初始化数组*/ while(n MaxVtNum) Vtn+ = 0; n = 0; while(# != ch) & (n MaxVtNum) if( != ch & n != ch & -1 = IndexCh(ch) Vt

17、n+ = ch; vtNum+; ch = getchar(); Vtn = #; k = n; if(# != ch) if( # != (ch = getchar() while(# != (ch = getchar() ; printf(n符号数目超过限制！n); inErr = 1; continue; Vtk = 0; ShowChArray(Vt); ch = ; while(y != ch & n != ch) if(n != ch) printf(输入正确确认?(y/n):); scanf(%c, &ch); if(n = ch) printf(录入错误重新输入！n); inE

18、rr = 1; else inErr = 0; /*产生式输入*/void InputP() char ch; int i = 0, n,num; printf(请输入文法产生式的个数：); scanf(%d, &num); PNum = num; getchar(); /*消除回车符*/ printf(n请输入文法的%d个产生式,并以回车分隔每个产生式：, num); printf(n); while(i num) printf(第%d个：, i); /*初始化*/ for(n =0; n MaxPLength; n+) buffern = 0; /*输入产生式串*/ ch = ; n =

19、0; while(n != (ch = getchar() & n rCursor = IndexCh(buffer3); pt-next = NULL; Pi.rHead = pt; n = 4; while(0 != buffern) qt = (pRNode*)malloc(sizeof(pRNode); qt-rCursor = IndexCh(buffern); qt-next = NULL; pt-next = qt; pt = qt; n+; Pi.rLength = n - 3; i+; else printf(输入符号含非法在成分，请重新输入！n); /*判断产生式正确性*/

20、bool CheckP(char * st) int n; if(100 IndexCh(st0) return false; if(- != st1) return false; if( != st2) return false; for(n = 3; 0 != stn; n +) if(-1 = IndexCh(stn) return false; return true;void First(int U) int i,j; for(i = 0; i PNum; i+) if(Pi.lCursor = U) struct pRNode* pt; pt = Pi.rHead; j = 0;

21、while(j pt-rCursor) AddFirst(U, pt-rCursor); break; else if(NULL = firstpt-rCursor - 100) First(pt-rCursor); AddFirst(U, pt-rCursor); if(!HaveEmpty(pt-rCursor) break; else pt = pt-next; j+; if(j = Pi.rLength) /*当产生式右部都能推出空时*/ AddFirst(U, -1); /*加入first集*/void AddFirst(int U, int nCh) struct collectN

22、ode *pt, *qt; int ch; /*用于处理Vn*/ pt = NULL; qt = NULL; if(nCh nVt = nCh) break; else qt = pt; pt = pt-next; if(NULL = pt) pt = (struct collectNode *)malloc(sizeof(struct collectNode); pt-nVt = nCh; pt-next = NULL; if(NULL = firstU - 100) firstU - 100 = pt; else qt-next = pt; /*qt指向first集的最后一个元素*/ pt

23、 = pt-next; else pt = firstnCh - 100; while(NULL != pt) ch = pt-nVt; if(-1 != ch) AddFirst(U, ch); pt = pt-next; bool HaveEmpty(int nVn) if(nVn nVt) return true; pt = pt-next; return false;void Follow(int V) int i; struct pRNode *pt ; if(100 = V) /*当为初始符时*/ AddFollow(V, -1, 0 ); for(i = 0; i rCursor

24、 != V) pt = pt-next; if(NULL != pt) pt = pt-next; if(NULL = pt) if(NULL = followPi.lCursor - 100 & Pi.lCursor != V) Follow(Pi.lCursor); AddFollow(V, Pi.lCursor, 0); else while(NULL != pt & HaveEmpty(pt-rCursor) AddFollow(V, pt-rCursor, 1); pt = pt-next; if(NULL = pt) if(NULL = followPi.lCursor - 100

25、 & Pi.lCursor != V) Follow(Pi.lCursor); AddFollow(V, Pi.lCursor, 0); else AddFollow(V, pt-rCursor, 1); void AddFollow(int V, int nCh, int kind) struct collectNode *pt, *qt; int ch; pt = NULL; qt = NULL; if(nCh nVt = nCh) break; else qt = pt; pt = pt-next; if(NULL = pt) pt = (struct collectNode *)mal

26、loc(sizeof(struct collectNode); pt-nVt = nCh; pt-next = NULL; if(NULL = followV - 100) followV - 100 = pt; else qt-next = pt; /*qt指向follow集的最后一个元素*/ pt = pt-next; else if(0 = kind) pt = follownCh - 100; while(NULL != pt) ch = pt-nVt; AddFollow(V, ch, 0); pt = pt-next; else pt = firstnCh - 100; while

27、(NULL != pt) ch = pt-nVt; if(-1 != ch) AddFollow(V, ch, 1); pt = pt-next; /*输出first或follow集*/void ShowCollect(struct collectNode *collect) int i; struct collectNode *pt; i = 0; while(NULL != collecti) pt = collecti; printf(n%c:t, Vni); while(NULL != pt) if(-1 != pt-nVt) printf( %c, Vtpt-nVt); else p

28、rintf( #); pt = pt-next; i+; printf(n);/*计算first和follow*/void FirstFollow() int i; i = 0; while(0 != Vni) if(NULL = firsti) First(100 + i); i+; i = 0; while(0 != Vni) if(NULL = followi) Follow(100 + i); i+; /*构造预测分析表*/void CreateAT() int i; struct pRNode *pt; struct collectNode *ct; for(i = 0; i rCu

29、rsor) ct = firstpt-rCursor - 100; while(NULL != ct) if(-1 != ct-nVt) analyseTablePi.lCursor - 100ct-nVt = i; ct = ct-next; pt = pt-next; if(NULL = pt) ct = followPi.lCursor - 100; while(NULL != ct) if(-1 != ct-nVt) analyseTablePi.lCursor - 100ct-nVt = i; else analyseTablePi.lCursor - 100vtNum = i; c

30、t = ct-next; else if(100 rCursor) /*不含空的非终结符*/ ct = firstpt-rCursor - 100; while(NULL != ct) analyseTablePi.lCursor - 100ct-nVt = i; ct = ct-next; else /*终结符或者空*/ if(-1 = pt-rCursor) ct = followPi.lCursor - 100; while(NULL != ct) if(-1 != ct-nVt) analyseTablePi.lCursor - 100ct-nVt = i; else /*当含有#号时

31、*/ analyseTablePi.lCursor - 100vtNum = i; ct = ct-next; else /*为终结符*/ analyseTablePi.lCursor - 100pt-rCursor = i; /*输出分析表*/void ShowAT() int i,j; printf(构造预测分析表如下：n); printf(t|t); for(i = 0; i vtNum; i+) printf(%ct, Vti); printf(#tn); printf(- - -t|- - -t); for(i = 0; i = vtNum; i+) printf(- - -t);

32、printf(n); for(i = 0; i vnNum; i+) printf(%ct|t, Vni); for(j = 0; j analyseStacktopAnalyse) if(analyseStacktopAnalyse = IndexCh(stcurrent) Pop(); current+; step+; printf(%dt, step); ShowStack(); printf(tt%ctt出栈、后移n, stcurrent); else printf(%c-%c不匹配！, analyseStacktopAnalyse, stcurrent); printf(此串不是此文法的句子！n); return; else /*当为非终结符时*/ r = analyseTableanalyseStacktopAnalyse - 100IndexCh(stcurrent); if(-1 != r) Push(r)