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我想明白爲什麼野牛以下規則BISON + FLEX的語法 - 爲什麼令牌被連接在一起
stmt:
declaration { ... }
| assignment { ... }
| exp { ... }
| ID ';' <-- this rule { ...
fprintf(stderr, "\n my id is '%s'", $1);
...
連接兩個記號，如果你檢查輸出會明白我的意思。我運行我的解析器，並將字符ab;輸入到程序中。根據我的野牛語法，這應該被解析爲ID，然後是;。並且在某種程度上它是發生了什麼。
然而，當我嘗試使用規則ID ';'方案產出ab;的$1變量，而不是我的ab。
運行程序
ab; <-- this my input to the program
#TOKEN 294[ID] yytext -> ab
Next token is token "identifier" (1.1:)
Shifting token "identifier" (1.1:)
Entering state 5
Reading a token:
#TOKEN 59[] yytext -> ;
Next token is token ';' (1.1:)
Shifting token ';' (1.1:)
Entering state 16
Reducing stack by rule 6 (line 133):
$1 = token "identifier" (1.1:) <-- first token which is 'ab'
$2 = token ';' (1.1:) <-- second token which is ';'
[stmt] 4:
my id is 'ab;' <-- the issue! This should be 'ab' not 'ab;'
ERROR: No such ID ab; found
-> $$ = nterm stmt (1.1:)
Stack now 0 1
Entering state 10
Reducing stack by rule 2 (line 126):
$1 = nterm prog (1.1:)
$2 = nterm stmt (1.1:)
-> $$ = nterm prog (1.1:)
Stack now 0
Entering state 1
Reading a token:
語法
%{
#include <stdio.h>
#include <string>
#include <map>
#include <math.h>
#include "noname-parse.h"
#include "noname-types.h"
extern int yylex(void);
extern void yyerror(const char *error_msg);
extern void division_by_zero(YYLTYPE &yylloc);
std::map<std::string, symrec*> symbol_table;
std::map<std::string, symrec*>::iterator symbol_table_it;
%}
//////////////////////////////////////////////////
///////////* Bison declarations. *///////////////
//////////////////////////////////////////////////
%union {
char* id_v;
double double_v;
long long_v;
symrecv symrecv;
char* error_msg;
};
%{
bool symbol_exist(const char* key) {
std::string skey = key;
symbol_table_it = symbol_table.find(skey);
return (symbol_table_it != symbol_table.end());
}
void symbol_insert(const char* key, symrecv symrecv) {
std::string skey = key;
symbol_table[skey] = symrecv;
}
symrecv symbol_retrieve(const char* key) {
std::string skey = key;
return symbol_table[skey];
}
void print_stmt(symrecv sym) {
if (sym->type == TYPE_LONG) {
fprintf(stderr, "%d", sym->value.intv);
} else if (sym->type == TYPE_DOUBLE) {
fprintf(stderr, "%lf", sym->value.doublev);
} else {
fprintf(stderr, "print not implemented for type %d", sym->type);
}
}
%}
%token LINE_BREAK "line_break"
// %token ';' "stmt_sep"
%token LETTER "letter"
%token DIGIT "digit"
%token DIGITS "digits"
%token DARROW "darrow"
%token ELSE "else"
%token FALSE "false"
%token IF "if"
%token IN "in"
%token LET "let"
%token LOOP "loop"
%token THEN "then"
%token WHILE "while"
%token BREAK "break"
%token CASE "case"
%token NEW "new"
%token NOT "not"
%token TRUE "true"
%token NEWLINE "newline"
%token NOTNEWLINE "notnewline"
%token WHITESPACE "whitespace"
%token LE "le"
%token ASSIGN "assign"
%token NULLCH "nullch"
%token BACKSLASH "backslash"
%token STAR "star"
%token NOTSTAR "notstar"
%token LEFTPAREN "leftparen"
%token NOTLEFTPAREN "notleftparen"
%token RIGHTPAREN "rightparen"
%token NOTRIGHTPAREN "notrightparen"
%token LINE_COMMENT "line_comment"
%token START_COMMENT "start_comment"
%token END_COMMENT "end_comment"
%token QUOTES "quotes"
%token ERROR "error"
%token <id_v> ID "identifier"
%token <double_v> DOUBLE "double"
%token <long_v> LONG "long"
%type <symrecv> assignment "assignment"
%type <symrecv> declaration "declaration"
%type <symrecv> exp "expression"
%type <symrecv> stmt "statement"
%left '-' '+'
%left '*' '/'
%left LET ID
%right '^' /* exponentiation */
%precedence NEG /* negation--unary minus */
%start prog
%%
//////////////////////////////////////////////////
///////////* The grammar follows. *///////////////
//////////////////////////////////////////////////
prog:
%empty
| prog stmt
;
stmt:
declaration { fprintf(stderr, "\n[stmt] 2: "); print_stmt($1); }
| assignment { fprintf(stderr, "\n[stmt] 3: "); print_stmt($1); }
| exp { fprintf(stderr, "\n[stmt] 1: "); print_stmt($1); }
| ID ';' { fprintf(stderr, "\n[stmt] 4: ");
fprintf(stderr, "\n my id is '%s'", $1);
$$ = (symrec *) malloc (sizeof (symrec));
if (!symbol_exist($1)) {
char buf[1024];
sprintf(buf, "No such ID %s found", $1);
yyerror(buf);
} else {
$$->name = $1;
$$->value.doublev = symbol_retrieve($1)->value.doublev;
printf("\nID %s -> %lf", $1, $$->value.doublev);
}
}
| error { printf("%d:%d", @1.first_column, @1.last_column); }
;
assignment:
ID ASSIGN exp ';' {
$$ = (symrec *) malloc (sizeof (symrec));
if (!symbol_exist($1)) {
char buf[1024];
sprintf(buf, "No such ID %s found", $1);
yyerror(buf);
} else {
$$->name = $1;
$$->type = $3->type;
$$->value.doublev = $3->value.doublev;
symbol_insert($1, $$);
// printf("\nID %s -> %lf", $1, $$->value.doublev);
printf("\n[assignment]");
}
}
| LET ID ASSIGN exp ';' {
$$ = (symrec *) malloc (sizeof (symrec));
if (symbol_exist($2)) {
char buf[1024];
sprintf(buf, "Cannot redefine ID %s", $2);
yyerror(buf);
} else {
$$->name = $2;
$$->type = $4->type;
$$->value.doublev = $4->value.doublev;
symbol_insert($2, $$);
// printf("\nID %s -> %lf", $1, $$->value.doublev);
printf("\n[assignment]");
}
}
;
declaration:
LET ID ';' {
$$ = (symrec *) malloc (sizeof (symrec));
if (symbol_exist($2)) {
char buf[1024];
sprintf(buf, "Cannot redefine ID %s", $2);
yyerror(buf);
} else {
$$->name = $2;
// $$->type = $1->type == TYPE_DOUBLE || $3->type == TYPE_DOUBLE ? TYPE_DOUBLE : $1->type;
symbol_insert($2, $$);
// $$->value.doublev = symbol_table_it->second->value.doublev;
// printf("\nID %s -> %lf", $1, $$->value.doublev);
printf("\n[declaration]");
}
}
;
exp:
LONG {
$$ = (symrec *) malloc (sizeof (symrec));
$$->name = (char*) "__annon";
$$->type = TYPE_LONG;
$$->value.intv = $1;
printf("\nexp %ld", $1);
}
| DOUBLE {
$$ = (symrec *) malloc (sizeof (symrec));
$$->name = (char*) "__annon";
$$->type = TYPE_DOUBLE;
$$->value.doublev = $1;
printf("\nexp %lf", $1);
}
| exp '+' exp {
// $$ = $1 + $3;
$$ = (symrec *) malloc (sizeof (symrec));
$$->name = (char*) "__annon";
$$->type = $1->type == TYPE_DOUBLE || $3->type == TYPE_DOUBLE ? TYPE_DOUBLE : $1->type;
$$->value.doublev = $1->value.doublev + $3->value.doublev;
printf("\nexp + exp %lf %lf", $1->value.doublev, $3->value.doublev);
}
| exp '-' exp {
// $$ = $1 - $3;
$$ = (symrec *) malloc (sizeof (symrec));
$$->name = (char*) "__annon";
$$->type = $1->type == TYPE_DOUBLE || $3->type == TYPE_DOUBLE ? TYPE_DOUBLE : $1->type;
$$->value.doublev = $1->value.doublev - $3->value.doublev;
printf("\nexp - exp %lf %lf", $1->value.doublev, $3->value.doublev);
}
| exp '*' exp {
// $$ = $1 * $3;
$$ = (symrec *) malloc (sizeof (symrec));
$$->name = (char*) "__annon";
$$->type = $1->type == TYPE_DOUBLE || $3->type == TYPE_DOUBLE ? TYPE_DOUBLE : $1->type;
$$->value.doublev = $1->value.doublev * $3->value.doublev;
printf("\nexp * exp %lf %lf", $1->value.doublev, $3->value.doublev);
}
| exp '/' exp {
$$ = (symrec *) malloc (sizeof (symrec));
$$->name = (char*) "__annon";
$$->type = $1->type == TYPE_DOUBLE || $3->type == TYPE_DOUBLE ? TYPE_DOUBLE : $1->type;
if ($3->value.doublev) {
// $$ = $1/$3;
$$->value.doublev = $1->value.doublev/$3->value.doublev;
} else {
// $$ = $1;
$$->value.doublev = $1->value.doublev;
division_by_zero(@3);
}
printf("\nexp/exp %lf %lf", $1->value.doublev, $3->value.doublev);
}
| '-' exp %prec NEG {
/**
* The %prec simply instructs Bison that the rule ‘| '-' exp’
* has the same precedence as NEG—in this case the next-to-highest
*/
// $$ = -($2->value.doublev);
$$ = (symrec *) malloc (sizeof (symrec));
$$->name = (char*) "__annon";
$$->type = $2->type;
$$->value.doublev = -$2->value.doublev;
printf("\nexp^exp %lf", $2->value.doublev);
}
| exp '^' exp {
//$$ = pow($1->value.doublev, $3->value.doublev);
$$ = (symrec *) malloc (sizeof (symrec));
$$->name = (char*) "__annon";
$$->type = $1->type;
$$->value.doublev = pow($1->value.doublev, $3->value.doublev);
printf("\nexp^exp %lf %lf", $1->value.doublev, $3->value.doublev);
}
| '(' exp ')' {
// $$ = $2->value.doublev;
$$ = (symrec *) malloc (sizeof (symrec));
$$->name = (char*) "__annon";
$$->type = $2->type;
$$->value.doublev = $2->value.doublev;
printf("\n(exp) %lf", $2->value.doublev);
}
| error { printf("\nERROR on exp rule"); }
;
%%
詞法
%{
#include "stdio.h"
#include "stdlib.h"
#include "lexer-utilities.h"
#include "noname-parse.h"
#include "noname-types.h"
int num_lines = 0, num_chars = 0;
extern YYSTYPE yylval;
extern void yyerror(char const *s);
extern int curr_lineno;
extern int verbose_flag;
unsigned int comment = 0;
%}
%option noyywrap
// %option noyywrap nounput batch debug yylineno
// %option warn noyywrap nodefault yylineno reentrant bison-bridge
%x COMMENT
%x STRING
LINE_BREAK \n
LETTER [a-zA-Z]
ALPHA [a-zA-Z$_]
DIGIT [0-9]
DIGITS {DIGIT}+
LONG {DIGIT}+
DOUBLE {DIGIT}+(\.{DIGIT}+)?
ID {ALPHA}({ALPHA}|{DIGIT})*
ELSE [eE][lL][sS][eE]
FALSE f[aA][lL][sS][eE]
IF [iI][fF]
IN [iI][nN]
LET [lL][eE][tT]
LOOP [lL][oO][oO][pP]
THEN [tT][hH][eE][nN]
WHILE [wW][hH][iI][lL][eE]
BREAK [bB][rR][eE][aA][kK]
CASE [cC][aA][sS][eE]
NEW [nN][eE][wW]
NOT [nN][oO][tT]
TRUE t[rR][uU][eE]
NEWLINE [\n]
NOTNEWLINE [^\n]
WHITESPACE [ \t\r\f\v]+
ASSIGN =
LE <=
DARROW =>
NULLCH [\0]
BACKSLASH [\\]
STAR [*]
NOTSTAR [^*]
LEFTPAREN [(]
NOTLEFTPAREN [^(]
RIGHTPAREN [)]
NOTRIGHTPAREN [^)]
LINE_COMMENT "--"
START_COMMENT "/*"
END_COMMENT "*/"
QUOTES \"
%%
{LINE_BREAK} {
++num_chars;
++num_lines;
}
{START_COMMENT} {
comment++;
BEGIN(COMMENT);
}
<COMMENT><<EOF>> {
yylval.error_msg = "EOF in comment";
BEGIN(INITIAL);
return (ERROR);
}
<COMMENT>{BACKSLASH}(.|{NEWLINE}) {
backslash_common();
};
<COMMENT>{BACKSLASH} ;
<COMMENT>{START_COMMENT} {
comment++;
}
<COMMENT>{END_COMMENT} {
comment--;
if (comment == 0) {
BEGIN(INITIAL);
}
}
<COMMENT>. { ++num_chars; }
<INITIAL>{END_COMMENT} {
yylval.error_msg = "Unmatched */";
return (ERROR);
}
<*>{WHITESPACE} { ++num_chars; }
<INITIAL>{ASSIGN} { return (ASSIGN); }
<INITIAL>{ELSE} { return (ELSE); }
<INITIAL>{IF} { return (IF); }
<INITIAL>{IN} { return (IN); }
<INITIAL>{LET} { return (LET); }
<INITIAL>{THEN} { return (THEN); }
<INITIAL>{WHILE} { return (WHILE); }
<INITIAL>{CASE} { return (CASE); }
<INITIAL>{NEW} { return (NEW); }
<INITIAL>{NOT} { return (NOT); }
<INITIAL>{ID} {
yylval.id_v = yytext;
return (ID); }
<INITIAL>{LONG} {
yylval.long_v = atoi(yytext);
return (LONG); }
<INITIAL>{DOUBLE} {
yylval.double_v = atof(yytext);
return (DOUBLE); }
<INITIAL>"," { return int(','); }
<INITIAL>":" { return int(':'); }
<INITIAL>"{" { return int('{'); }
<INITIAL>"}" { return int('}'); }
<INITIAL>"+" { return int('+'); }
<INITIAL>"-" { return int('-'); }
<INITIAL>"*" { return int('*'); }
<INITIAL>"/" { return int('/'); }
<INITIAL>"<" { return int('<'); }
<INITIAL>"~" { return int('~'); }
<INITIAL>"." { return int('.'); }
<INITIAL>"@" { return int('@'); }
<INITIAL>"(" { return int('('); }
<INITIAL>")" { return int(')'); }
<INITIAL>"&" { return int('&'); }
<INITIAL>";" { return int(';'); }
<INITIAL>. {
printf("lexer error '%s'", yytext);
yylval.error_msg = yytext; return 0;
}
%%