Yacc and Bison Parser Grammar Definitions

Posted on May 17, 2026 in Service Computing

1. Basic Structure and Token Definitions

typedef struct s_attr { int value; char *code; } t_attr;

#define YYSTYPE t_attr
%token N ID INTEGER STRING MAIN WHILE
%token AND OR IGUAL DISTINTO MENORIGUAL MAYORIGUAL

Operator Precedence

  • %right '='
  • %left OR
  • %left AND
  • %left IGUAL DISTINTO
  • %left '<' '>' MENORIGUAL MAYORIGUAL
  • %left '+' '-'
  • %left '*' '/' '%'
  • %left UNARY_SIGN

2. Grammar Rules and Semantic Actions

Variable and Main Function Parsing

a: dg dm

dg: /* */ | dg INTEGER lv ';' { p("%s\n", $3.c); }

lv: ID { sp(t, "(setq %s 0)", $1.c); $$.c = gc(t); }
| ID '=' N { sp(t, "(setq %s %d)", ... )
| lv ',' ID { sp(t, "%s (setq %s 0)", ... )
| lv ',' ID '=' N { sp(t, "%s (setq %s %d)", ... )

dm: MAIN '(' ')' '{' ap '}' { p("(defun main ()\n %s\n)\n", $5.c); }

Control Flow and Expressions

ap: /* */ { $$.c = gc(""); }
| ap sentencia ';' { sp(t, "%s\n %s", $1.c, $2.c); $$.c = gc(t); }
| ap WHILE '(' e ')' '{' ap '}' { sp(t, "%s\n (loop while %s do\n %s)", $1.c, $4.c, $7.c); $$.c = gc(t); }

3. Advanced Functionality and AST Generation

This section covers complex structures including IF, FOR, SWITCH, and ARRAY handling, as well as Abstract Syntax Tree (AST) generation patterns for different compiler targets.

Function and Loop Logic

fun: ID { strcpy(current_scope, $1.c); local_sym_count = 0; } '(' param ')' '{' cf '}' { sp(t, "(defun %s (%s)\n %s\n)", $1.c, $4.c, $7.c); ... }

Case and Array Handling

lc: CASE N':' cf BREAK ';' { sp(t, "(%d\n %s)", $2.V, $4.c); $$.c = gc(t); }
| ID '[' N']' { av($1.c); sp(t, "(setq %s (make-array %d))", gvn($1.c), $3.V); $$.c = gc(t); }