2 exp exp op expexpnumber op 34 exp

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简单整型算术表达式文法： exp → exp op exp|(exp)|number op → +|-|* 符号串 3+4的最左推导: exp op exp number + number 7

1 exp 2 exp 3 op 4 exp number + number 3+4的分析树 8

简单整型算术表达式文法： exp → exp op exp|(exp)|number op → +|-|* exp exp op number exp + number 3+4的最右推导 9

1 exp 4 op 3 number + exp 2 number 3+4的分析树 10

Typedef enum {Plus, Minus, Times} Op. Kind; Typedef enum {Op. Kind, Const. Kind} Exp. Kind; Typedef struct streenode { Exp. Kind kind; Op. Kind op; struct streenode *lchild, *rchild; int val; }Stree. Node Typedef Stree. Node *Syntax. Tree; 14

cabd 变量token存储当前扫描的下一个单词 void match(expected. Token); { if token=expected. Token token = get. Token(); else error; } 24

void S(void) { match(c); A(); match(d); } void A(void) { match(a); match(b); } 25

识别S的递归下降函数的伪代码： void S(void) void A 1(void) { match(c); { match(a); A 1(); //记住当前的token位置 } match(d); void A 2(void) if(error) then { match(a); { A 2(); match(b); match(d); } } } 27

例4 -4：一个简化了的if文法规则： if-stmt→if (exp) statement |if (exp) statement else statement 写出识别if-stmt的递归下降函数的伪代码 33

viod if. Stmt(void) { match(if); match((); exp(); match()); statement(); if token = else then { match(else); statement(); } } 35

2. 重复情况：简单整型算术表达式文法： exp→exp addop term|term addop→+|term→term mulop factor|factor mulop→* factor→(exp)|number 写出识别表达式exp的递归下降函数的伪代码 36

viod exp(void) { term( ); while token=+ or token={ match(token); term( ); } } 40

简单整型算术表达式文法： exp→exp addop term|term addop→+|term→term mulop factor|factor mulop→* factor→(exp)|number 写出识别表达式exp的完整的递归下降函数的伪代码？ 41

if语句的抽象语法树结构： if-stmt if exp then stmt-sequence[else stmt-sequence]end 49

repeat 语句 repeat-stmt repeat stmt-sequence until exp 50

assign 语句 assign_stmt identifier : = exp 51

write语句 write_stmt write exp read语句 read_stmt read identifier 52

typedef enum{Stmt. K, Exp. K}Node. Kind; typedef enum{If. K, Repeat. K, Assign. K, Read. K, Write. K}Stmt. Kind; typedef enum{Op. K, Const. K, Id. K}Exp. Kind; typedef enum{Void, Integer, Boolean}Exp. Type; #define MAXCHILDREN 3 54

typedef struct tree. Node {struct tree. Node* child[MAXCHILDREN]; struct tree. Node* sibling; int lineno; Node. Kind nodekind; union{ Stmt. Kind stmt; Exp. Kind exp; } kind; union{ Token. Type op; int val; char * name; } attr; Exp. Type type; } Tree. Node; 55

Tiny语言的递归下降分析函数如下：PARSE. C 一个输出其输入阶乘的TINY语言程序 read x; if x>0 then fact: =1; repeat fact: =fact* x; x: =x-1 until x=0; write fact end 56

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一个输出其输入阶乘的TINY语言程序 read x; if x>0 then fact: =1; repeat fact: =fact* x; x: =x-1 until x=0; write fact end 58

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例4 -3：考虑下述简单整型表达式文法，求各非终结符的First()集合； (1) exp→exp addop term (2) exp→term (3) addop→+ (4) addop→(5) term→term mulop factor (6) term → factor (7) mulop→* (8) factor→(exp) (9) factor→number 75

First(addop)= {+, -} First(mulop)= {*} First(term)= {(, number} First(factor)= {(, number} First(exp)= {(, number} 76

例4 -5：考虑下述简单整型表达式文法，求各非终结符的Follow()集合； (1) exp→exp addop term (2) exp→term (3) addop→+ (4) addop→(5) term→term mulop factor (6) term → factor (7) mulop→* (8) factor→(exp) (9) factor→number 81

Follow(exp)= {$, +, -, )} Follow(addop)= {(, number} Follow(term)= {$, +, -, *, )} Follow(mulop)= {(, number} Follow(factor)= {$, +, -, *, )} 82

Follow(T’) Follow(T) Follow(F) First(T’) Follow(T) 85

a. 所求得的各非终结符的First集合和 Follow集合如下： First(declaration)={int, float} First(type) ={int, float} First(var-list) ={identifier} First(list) ={, , } 90

Follow(declaration)={$} Follow(type)={identifier} Follow(var-list)={$} Follow(list) ={$} 91

对各产生式进行编号： r 1: declaration→type var-list r 2: r 3: r 4: r 5: type→int type→ float var-list→identifier list → , var-list r 6: list → b. 构造该文法的LL(1)分析表。 92