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심볼 테이블

miniC.l

%%
[a-zA-Z]    { yylval = alloc(TOKEN); return OPERAND; }
[ \t]        ;
.        return yytext[0];
\n        { lineno++; return yytext[0]; }
%%
yywrap ()
{ return 1;  /* terminate when reaching end of stdin */ }

miniC.y

%{
#include <stdio.h>

typedef char * string;

#define YYSTYPE string
#define TOKEN 1
#define TEMP 0

int temp = 0;
struct node {
    char name[3];
    struct node * next;
};
struct node * tlist = NULL;
char * alloc (int type);
%}
%token OPERAND
%left '+' '-'
%left '*' '/'
%left UMINUS UPLUS
%%
List:        /* empty list */
        | List '\n'
        | List Expr '\n' { clear(); }
        ;
Expr:        '+' Expr %prec UPLUS { $$ = $2; }
        | '-' Expr %prec UMINUS { $$ = alloc(TEMP);
            atom("NEG", $2, 0, $$); }
        | Expr '+' Expr { $$ = alloc(TEMP);
            atom ("ADD", $1, $3, $$); }
        | Expr '-' Expr { $$ = alloc(TEMP);
            atom ("SUB", $1, $3, $$); }
        | Expr '*' Expr { $$ = alloc(TEMP);
            atom ("NUL", $1, $3, $$); }
        | Expr '/' Expr { $$ = alloc(TEMP);
            atom ("DIV", $1, $3, $$); }
        | '(' Expr ')' { $$ = $2; }
        | OPERAND { $$ = $1; }
        ;
%%
char *progname;
int lineno = 1;
#include "lex.yy.c"

main (int argc, char *argv[])
{
  progname = argv[0];
  yyparse();
}

yyerror (char * s)
{
  fprintf(stderr, "%s[%d]: %s\n", progname, lineno, s);
}

char * alloc(int type)
{
    static struct node * last = NULL;
    static struct node * ptr;
    static char t[3] = "   ";

    ptr = (struct node *) malloc (sizeof (struct node));
    ptr -> next = NULL;
    if (last != NULL) {
        last->next = ptr;
        last = ptr;
    }
    else
        tlist = last = ptr;
    if (type == TEMP) {
        t[0] = 'T';
        t[1] = '0' + temp++;
        strcpy(last->name, t);
    }
    else
        strcpy(last->name, yytext);

    return (char *) last;

}

clear()
/* free up allocated memory, reset counters for next Expr */
{
    struct node * ptr;
    while (tlist) {
        ptr = tlist->next;
        free(tlist);
        tlist = ptr;
    }
    temp = 0;
}

atom (char * operation, char * operand1, char * operand2,
             char * result)
/* put out an atom. */
{
    if (operand2)    /* NEG has only one operand and result */
        printf("%\t%s %s %s %s\n", operation, operand1, operand2, result);
    else
        printf("%\t%s %s %s\n", operation, operand1, result);
}

$ ./miniC
(a+b)*c
        ADD a b T0
        MUL T0  c T1
-a+b*c
        NEG a T0
        MUL b c T1
        ADD T0  T1  T2
^D

$

참조 사이트:

http://elvis.rowan.edu/~bergmann/books.html