Search - symbol factor

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[ELanguage] pl/0 DL : 0: /*PL/0编译系统C版本头文件pl0.h*/ /* typedef enum { false, true } bool; */ #define norw 13 /*关键字个数*/ #define txmax 100 /*名字表容量*/ #define nmax 14 /*number的最大位数*/ #define al 10 /*符号的最大长度*/ #define amax 2047 /*地址上界*/ #define levmax 3 /*最大允许过程嵌套声明层数[0,levmax]*/ #define cxmax 200 /*最多的虚拟机代码数*/ /*符号*/ enum symbol{ nul, ident, number, plus, minus, times, slash, oddsym, eql, neq, lss, leq, gtr, geq, lparen, rparen, comma, semicolon, period, becomes, beginsym, endsym, ifsym, thensym, whilesym, writesym, readsym, dosym, callsym, constsym, varsym, procsym, }; #define symnum 32 /*名字表中的类型*/ enum object{ constant, variable, procedur, }; /*虚拟机代码*/ enum fct{ lit, opr, lod, sto, cal, inte, jmp, jpc, }; #define fctnum 8 /*虚拟机结构代码*/ struct instruction { /*454*/ enum fct f; // 虚拟机代码指令 int l; //引用层与声明层的层次差 int a; //根据f的不同而不同 }; FILE * fas; //输出名字表 FILE * fa; //输出虚拟机代码 FILE * fa1; //输出源文件及其各行对应的首地址 FILE * fa2; //输出结果 bool listswitch; //显示虚拟机代码与否 bool tableswitch; //显示名字与否 char ch; //获取字符的缓冲区，getch使用 enum symbol sym; //当前的符号 char id[al+1]; //当前ident，多出的一个字节用于存放0 int num; //当前number int cc,ll; //getch使用的计数器，cc表示当前字符(ch)的位置 int cx; //虚拟机代码指针，取值范围[0，cxmax-1] char line[81]; //读取行缓冲区 char a[al+1]; //临时符号，多出的一个字节用于存放0 struct instruction code[cxmax]; //存放虚拟机代码的数组 char word[norw][al]; //保留字 enum symbol wsym[norw]; //保留字对应的符号值 enum symbol ssym[256]; //单字符的符号值 char mnemonic[fctnum][5]; //虚拟机代码指令名称 bool declbegsys[symnum]; //表示声明开始的符号集合 bool statbegsys[symnum]; //表示语句开始的符号集合 bool facbegsys[symnum]; //表示因子开始的符号集合 //名字表结构 struct tablestruct { char name[al]; //名字 enum object kind; //类型：const，var，array or procedure int val; //数值，仅const使用 int level; //所须层，仅const不能用 int adr; //地址，仅const不能用 int size; //需要分配的数据空间，仅procedure使用 }; struct tablestruct table[txmax]; //名字表 FILE * fin; FILE * fout; char fname[al]; int err; //错误计数器 //当函数中发生fatal error时，返回-1告知调用它的函数，最终退出程序 #define getsymdo if(-1==getsym()) return -1 #define getchdo if(-1==getch()) return -1 #define testdo(a,b,c) if(-1==test(a,b,c)) return -1 #define gendo(a,b,c) if(-1==gen(a,b,c)) return -1 #define expressiondo(a,b,c) if(-1==expression(a,b,c)) return -1 #define factordo(a,b,c) if(-1==factor(a,b,c)) return -1 #define termdo(a,b,c) if(-1==term(a,b,c)) return -1 #define conditiondo(a,b,c) if(-1==condition(a,b,c)) return -1 #define statementdo(a,b,c) if(-1==statement(a,b,c)) return -1 #define constdeclarationdo(a,b,c) if(-1==constdeclaration(a,b,c)) return -1 #define vardeclarationdo(a,b,c) if(-1==vardeclaration(a,b,c)) return -1 void error(int n); int getsym(); int getch(); void init(); int gen(enum fct x,int y ,int z); int test(bool *s1,bool *s2,int n); int inset(int e,bool *s); int addset(bool *str,bool * s1,bool * s2,int n); int subset(bool *str,bool * s1,bool * s2,int n); int mulset(bool *str,bool * s1,bool * s2,int n); int block(int lev,int tx,bool * fsys); void interpret(); int factor(bool * fsys,int * ptx,int lev); int term(bool * fsys,int * ptx,int lev); int condition(bool * fsys,int * ptx,int lev); int expression(bool * fsys,int * ptx,int lev); int statement(bool * fsys,int * ptx,int lev); void listcode(int cx0); int vardeclaration(int *ptr, int lev,int *ptx); int constdeclaration(int *ptr, int lev,int *ptx); int position(char * idt,int tx); void enter(enum object k,int * ptx,int lev, int * pdx); int base(int l,int * s,int b)
Date : 2010-09-13 Size : 24.55kb User : xqq771084591
[ELanguage] diguixiajiang DL : 0: 递归下降的基本思想：为每一个非终结符构造一个子程序，每一个子程序的过程体中按该产生式的候选项分情况展开，遇到终结符直接匹配，而遇到非终结符就调用相应非终结符的子程序。该分析从调用文法开始符号的子程序开始，直到所有非终结符都展开为终结符并得到匹配为止。若分析过程中达到这一步则表明分析成功，否则表明输入中有语法错误。递归下降分析对文法的限制是不能有公共左因子和左递归。由于文法是递归定义的，因此子程序也是递归的，被称为递归下降子程序。 -The basic idea of recursive descent: For each non-terminal construct a subroutine, each subroutine of the process of the body produced by the sub-type of candidate to undertake encountered terminator direct match, while the case of non-terminal symbol on the call to the corresponding non-terminal symbol of the subroutine. The analysis from the grammar start symbol of the subroutine call to start until all the non-terminal and launched as a terminator and get matched up. If the analysis process to achieve this step indicates that the analysis of success, or else that there is a syntax error input. Recursive descent analysis of the grammar of the restrictions can not have public left factor and left recursion. As the grammar is a recursive definition, and therefore also a recursive subroutine, known as recursive descent subprogram.
Date : 2025-12-25 Size : 1kb User : WM
[ELanguage] GrammerParsers DL : 0: 利用C++语言编制一个LL（1）语法分析器，利用LL(1)控制程序根据显示栈栈顶内容、向前看符号以及LL（1）分析表，对输入符号串自上而下的分析过程。可通过消除左递归、提取左因子把非LL(1)文法改造成LL(1)文法。-Compiled using a C++ language LL (1) parser using LL (1) control program according to display the contents of the stack the stack, forward-looking symbols and LL (1) of the table, the input symbol string of top-down analysis . Through the elimination of left recursion, left-factor of the extraction of non-LL (1) grammar transformation into a LL (1) grammar.
Date : 2025-12-25 Size : 222kb User : 杨玥