如何使用yacc生成c语言语法

分析器？

要使用 yacc 生成 C 语言的语法分析器，需要以下步骤：

1. 编写一个语法描述文件，也称为 .y 文件，用来定义语言的语法结构和相应的语义动作。

2. 使用 yacc 工具来将该语法描述文件编译生成相应的 C 语言代码。

3. 编译上一步中生成的 C 语言代码并运行，即可使用生成的语法分析器来解析相应的代码。

具体使用方法请参考 yacc 工具的使用手册或者相关教程。

相关问题

使用lex,yacc实现C语言的词法分析、语法分析，最后输出抽象语法树(AST),不要求typedef，#define复杂语法，给出完整详细的lex代码和yacc代码

本问题所需的代码较为复杂，无法在此处全部展示。以下是一个简化版本，供参考：

1. Lex代码：

%{
#include <stdio.h>
#include <stdlib.h>
#include "y.tab.h"
%}

%%

"int"           { return INT; }
"float"         { return FLOAT; }
"char"          { return CHAR; }
"double"        { return DOUBLE; }
"if"            { return IF; }
"else"          { return ELSE; }
"while"         { return WHILE; }
"for"           { return FOR; }
"do"            { return DO; }
"return"        { return RETURN; }
[0-9]+          { yylval.num = atoi(yytext); return NUM; }
[a-zA-Z_][a-zA-Z0-9_]*   { yylval.str = strdup(yytext); return ID; }
"=="            { return EQ; }
"!="            { return NE; }
">="            { return GE; }
"<="            { return LE; }
">"             { return GT; }
"<"             { return LT; }
"="             { return ASSGN; }
"+"             { return PLUS; }
"-"             { return MINUS; }
"*"             { return MULT; }
"/"             { return DIV; }
"%"             { return MOD; }
"("             { return LPAREN; }
")"             { return RPAREN; }
"{"             { return LBRACE; }
"}"             { return RBRACE; }
";"             { return SEMICOLON; }
","             { return COMMA; }
"["             { return LBRACKET; }
"]"             { return RBRACKET; }
"'"             { return SQUOTE; }
\"              { return DQUOTE; }
[ \t\n]         ; /* ignore white space */

.               { printf("Unknown token: %s\n", yytext); }
%%

int yywrap() {
    return 1;
}

2. Yacc代码：

%{
#include <stdio.h>
#include <stdlib.h>
#include "tree.h"
%}

%union {
    int num;
    char *str;
    Node *node;
}

%token <num> NUM
%token <str> ID
%token INT FLOAT CHAR DOUBLE IF ELSE WHILE FOR DO RETURN
%token EQ NE GE LE GT LT ASSGN PLUS MINUS MULT DIV MOD LPAREN RPAREN LBRACE RBRACE SEMICOLON COMMA LBRACKET RBRACKET SQUOTE DQUOTE

%type <node> program decl_list decl var_list var stmt_list stmt expr term factor

%start program

%%

program: decl_list {
    $$ = create_node(PROGRAM, $1, NULL, NULL);
}

decl_list: /* empty */ {
    $$ = NULL;
}
| decl_list decl {
    $$ = create_node(DECL_LIST, $1, $2, NULL);
}

decl: type var_list SEMICOLON {
    $$ = create_node(DECL, $1, $2, NULL);
}

type: INT {
    $$ = create_node(TYPE, "int", NULL, NULL);
}
| FLOAT {
    $$ = create_node(TYPE, "float", NULL, NULL);
}
| CHAR {
    $$ = create_node(TYPE, "char", NULL, NULL);
}
| DOUBLE {
    $$ = create_node(TYPE, "double", NULL, NULL);
}

var_list: var {
    $$ = create_node(VAR_LIST, $1, NULL, NULL);
}
| var_list COMMA var {
    $$ = create_node(VAR_LIST, $1, $3, NULL);
}

var: ID {
    $$ = create_node(VAR, $1, NULL, NULL);
}
| ID LBRACKET NUM RBRACKET {
    $$ = create_node(VAR, $1, create_node(NUMBER, $3, NULL, NULL), NULL);
}

stmt_list: /* empty */ {
    $$ = NULL;
}
| stmt_list stmt {
    $$ = create_node(STMT_LIST, $1, $2, NULL);
}

stmt: expr SEMICOLON {
    $$ = create_node(EXPR_STMT, $1, NULL, NULL);
}
| LBRACE stmt_list RBRACE {
    $$ = create_node(BLOCK, $2, NULL, NULL);
}
| IF LPAREN expr RPAREN stmt {
    $$ = create_node(IF_STMT, $3, $5, NULL);
}
| IF LPAREN expr RPAREN stmt ELSE stmt {
    $$ = create_node(IF_ELSE_STMT, $3, $5, $7);
}
| WHILE LPAREN expr RPAREN stmt {
    $$ = create_node(WHILE_STMT, $3, $5, NULL);
}
| FOR LPAREN expr SEMICOLON expr SEMICOLON expr RPAREN stmt {
    $$ = create_node(FOR_STMT, create_node(EXPR_STMT, $3, NULL, NULL), create_node(EXPR_STMT, $5, NULL, NULL), create_node(EXPR_STMT, $7, NULL, NULL), $9);
}
| DO stmt WHILE LPAREN expr RPAREN SEMICOLON {
    $$ = create_node(DO_WHILE_STMT, $4, $2, NULL);
}
| RETURN expr SEMICOLON {
    $$ = create_node(RETURN_STMT, $2, NULL, NULL);
}

expr: term {
    $$ = create_node(EXPR, $1, NULL, NULL);
}
| expr PLUS term {
    $$ = create_node(PLUS_EXPR, $1, $3, NULL);
}
| expr MINUS term {
    $$ = create_node(MINUS_EXPR, $1, $3, NULL);
}

term: factor {
    $$ = create_node(TERM, $1, NULL, NULL);
}
| term MULT factor {
    $$ = create_node(MULT_TERM, $1, $3, NULL);
}
| term DIV factor {
    $$ = create_node(DIV_TERM, $1, $3, NULL);
}
| term MOD factor {
    $$ = create_node(MOD_TERM, $1, $3, NULL);
}

factor: NUM {
    $$ = create_node(NUMBER, $1, NULL, NULL);
}
| ID {
    $$ = create_node(IDENTIFIER, $1, NULL, NULL);
}
| ID LBRACKET expr RBRACKET {
    $$ = create_node(ARRAY_ACCESS, $1, $3, NULL);
}
| LPAREN expr RPAREN {
    $$ = create_node(EXPR, $2, NULL, NULL);
}
| MINUS factor {
    $$ = create_node(NEG_FACTOR, $2, NULL, NULL);
}
| factor PLUS PLUS {
    $$ = create_node(POST_INC_FACTOR, $1, NULL, NULL);
}
| factor MINUS MINUS {
    $$ = create_node(POST_DEC_FACTOR, $1, NULL, NULL);
}
| SQUOTE ID SQUOTE {
    $$ = create_node(CHARACTER, $2, NULL, NULL);
}
| DQUOTE ID DQUOTE {
    $$ = create_node(STRING, $2, NULL, NULL);
}
| func_call {
    $$ = create_node(EXPR_STMT, $1, NULL, NULL);
}

func_call: ID LPAREN arg_list RPAREN {
    $$ = create_node(FUNC_CALL, $1, $3, NULL);
}

arg_list: /* empty */ {
    $$ = NULL;
}
| expr {
    $$ = create_node(ARG_LIST, $1, NULL, NULL);
}
| arg_list COMMA expr {
    $$ = create_node(ARG_LIST, $1, $3, NULL);
}

%%

int yylex();
void yyerror(char *);

int main() {
    yyparse();
    return 0;
}

void yyerror(char *s) {
    printf("%s\n", s);
}

以上代码演示了如何使用lex和yacc实现C语言的词法分析、语法分析，并输出抽象语法树。具体实现中还需要定义Node结构体和相关的操作函数，以及将yacc生成的AST传递到下一步的代码生成中。

使用lex和yacc编写一个C语言的语法分析器

以下是一个基本的C语言语法分析器示例，使用lex和yacc编写：

1. 首先，我们需要定义我们的C语言语法规则。下面是一个简单的示例：

program -> declaration_list

declaration_list -> declaration | declaration_list declaration

declaration -> var_declaration | func_declaration

var_declaration -> type_specifier ID ;

type_specifier -> int | float | double | char

func_declaration -> type_specifier ID ( params ) compound_stmt

params -> param_list | void

param_list -> param | param_list , param

param -> type_specifier ID

compound_stmt -> { local_declarations statement_list }

local_declarations -> local_declarations var_declaration | ε

statement_list -> statement | statement_list statement

statement -> expression_stmt | compound_stmt | selection_stmt | iteration_stmt | return_stmt

expression_stmt -> expression ;

selection_stmt -> if ( expression ) statement | if ( expression ) statement else statement

iteration_stmt -> while ( expression ) statement

return_stmt -> return ; | return expression ;

expression -> var = expression | simple_expression

var -> ID

simple_expression -> additive_expression relop additive_expression | additive_expression

additive_expression -> additive_expression addop term | term

term -> term mulop factor | factor

factor -> ( expression ) | var | call | NUM

call -> ID ( args )

args -> arg_list | ε

arg_list -> expression | arg_list , expression

2. 接下来，我们使用lex编写一个词法分析器，它将读取C代码并将其分解为标记流。以下是一个简单的示例：

%{
#include "y.tab.h"
%}

%%

"auto"          return AUTO;
"break"         return BREAK;
"case"          return CASE;
"char"          return CHAR;
"const"         return CONST;
"continue"      return CONTINUE;
"default"       return DEFAULT;
"do"            return DO;
"double"        return DOUBLE;
"else"          return ELSE;
"enum"          return ENUM;
"extern"        return EXTERN;
"float"         return FLOAT;
"for"           return FOR;
"goto"          return GOTO;
"if"            return IF;
"int"           return INT;
"long"          return LONG;
"register"      return REGISTER;
"return"        return RETURN;
"short"         return SHORT;
"signed"        return SIGNED;
"sizeof"        return SIZEOF;
"static"        return STATIC;
"struct"        return STRUCT;
"switch"        return SWITCH;
"typedef"       return TYPEDEF;
"union"         return UNION;
"unsigned"      return UNSIGNED;
"void"          return VOID;
"volatile"      return VOLATILE;
"while"         return WHILE;

[0-9]+          yylval.num = atoi(yytext); return NUM;
[a-zA-Z]+       yylval.name = strdup(yytext); return ID;
[ \t\n]         /* ignore whitespace */
.               return yytext[0];

%%

int yywrap() {
    return 1;
}

3. 最后，我们使用yacc编写语法分析器，它将使用我们的语法规则和词法分析器生成的标记流来分析C代码。以下是一个简单的示例：

%{
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
%}

%token ID NUM AUTO BREAK CASE CHAR CONST CONTINUE DEFAULT DO DOUBLE ELSE ENUM EXTERN FLOAT FOR GOTO IF INT LONG REGISTER RETURN SHORT SIGNED SIZEOF STATIC STRUCT SWITCH TYPEDEF UNION UNSIGNED VOID VOLATILE WHILE

%%

program: declaration_list
    ;

declaration_list: declaration
    | declaration_list declaration
    ;

declaration: var_declaration
    | func_declaration
    ;

var_declaration: type_specifier ID ';'
    ;

type_specifier: INT
    | FLOAT
    | DOUBLE
    | CHAR
    ;

func_declaration: type_specifier ID '(' params ')' compound_stmt
    ;

params: param_list
    | VOID
    ;

param_list: param
    | param_list ',' param
    ;

param: type_specifier ID
    ;

compound_stmt: '{' local_declarations statement_list '}'
    ;

local_declarations: local_declarations var_declaration
    | /* empty */
    ;

statement_list: statement
    | statement_list statement
    ;

statement: expression_stmt
    | compound_stmt
    | selection_stmt
    | iteration_stmt
    | return_stmt
    ;

expression_stmt: expression ';'
    ;

selection_stmt: IF '(' expression ')' statement
    | IF '(' expression ')' statement ELSE statement
    ;

iteration_stmt: WHILE '(' expression ')' statement
    ;

return_stmt: RETURN ';'
    | RETURN expression ';'
    ;

expression: var '=' expression
    | simple_expression
    ;

var: ID
    ;

simple_expression: additive_expression relop additive_expression
    | additive_expression
    ;

additive_expression: additive_expression addop term
    | term
    ;

term: term mulop factor
    | factor
    ;

factor: '(' expression ')'
    | var
    | call
    | NUM
    ;

call: ID '(' args ')'
    ;

args: arg_list
    | /* empty */
    ;

arg_list: expression
    | arg_list ',' expression
    ;

relop: '<'
    | LE
    | '>'
    | GE
    | EQ
    | NE
    ;

addop: '+'
    | '-'
    ;

mulop: '*'
    | '/'
    ;

%%

int main() {
    yyparse();
    return 0;
}

void yyerror(char *s) {
    printf("Error: %s\n", s);
}

这是一个基本的C语言语法分析器示例，它将读取C代码并检查它是否符合我们的语法规则。需要注意的是，这只是一个简单的示例，实际的C语言语法规则远比这个复杂，因此需要更复杂的词法和语法规则来处理它。