UNIX — универсальная среда программирования - Керниган Брайан Уилсон

 int narg; /* number of arguments */

}

%token <sym> NUMBER STRING PRINT VAR BLTIN UNDEF WHILE IF ELSE

%token <sym> FUNCTION PROCEDURE RETURN FUNC PROC READ

%token <narg> ARG

%type <inst> expr stmt asgn prlist stmtlist

%type <inst> cond while if begin end

%type <sym> procname

%type <narg> arglist

%right '='

%left OR

%left AND

%left GT GE LT LE EQ NE

%left '+' '-' %left '/'

%left UNARYMINUS NOT

%right '^'

%%

list: /* nothing */

 | list 'n'

 | list defn 'n'

 | list asgn 'n' { code2(pop, STOP); return 1; }

 | list stmt 'n' { code(STOP); return 1; }

 | list expr 'n' { code2(print, STOP); return 1; }

 | list error 'n' { yyerrok; }

 ;

asgn: VAR '=' expr { code3(varpush,(Inst)$1,assign); $$=$3; }

 | ARG '=' expr

 { defnonly("$"); code2(argassign,(Inst)$1); $$=$3;}

 ;

stmt: expr { code(pop); }

 | RETURN { defnonly("return"); code(procret); }

 | RETURN expr

 { defnonly("return"); $$=$2; code(funcret); }

 | PROCEDURE begin '(' arglist ')'

 { $$ = $2; code3(call, (Inst)$1, (Inst)$4); }

 | PRINT prlist { $$ = $2; }

 | while cond stmt end {

  ($1)UID = (Inst)$3; /* body of loop */

  ($1)[2] = (Inst)$4;

 } /* end, if cond fails */

 | if cond stmt end { /* else-less if */

  ($1)[1] = (Inst)$3; /* thenpart */

  ($1)[3] = (Inst)$4;

 } /* end, if cond fails */

 | if cond stmt end ELSE stmt end { /* if with else */

  ($1)[1] = (Inst)$3; /* thenpart */

  ($1)[2] = (Inst)$6; /* elsepart */

  ($1)[3] = (Inst)$7;

 } /* end, if cond fails */

 | '{' stmtlist '}' { $$ = $2; }

 ;

cond: '(' expr ')' { code(STOP); $$ = $2; }

 ;

while: WHILE { $$ = code3(whilecode,STOP,STOP); }

 ;

if: IF { $$ = code(ifcode); code3(STOP,STOP,STOP); }

 ;

begin: /* nothing */ { $$ = progp; }

 ;

end: /* nothing */ { code(STOP); $$ = progp; }

 ;

stmtlist: /* nothing */ { $$ = progp; }

 | stmtlist 'n'

 | stmtlist stmt

 ;

expr: NUMBER { $$ = code2(constpush, (Inst)$1); }

 | VAR { $$ = code3(varpush, (Inst)$1, eval); }

 | ARG { defnonly("$"); $$ = code2(arg, (Inst)$1); }

 | asgn

 | FUNCTION begin '(' arglist ');

 { $$ = $2; code3(call,(Inst)$1,(Inst)$4); }

 | READ '(' VAR ')'{$$ = code2(varread, (Inst)$3); }

 | BLTIN '(' expr ')' { $$=$3; code2(bltin, (Inst)$1->u.ptr); }

 | '(' expr ')' { $$ = $2; }

 | expr '+' expr { code(add); }

 | expr '-' expr { code(sub); }

 | expr '*' expr { code(mul); }

 | expr '/' expr { code(div); }

 | expr '^' expr { code(power); }

 | '-' expr %prec UNARYMINUS { $$=$2; code(negate); }

 | expr GT expr { code(gt); }

 | expr GE expr { code(ge); }

 | expr LT expr { code(lt); }

 | expr LE expr { code(le); }

 | expr EQ expr { code(eq); }

 | expr NE expr { code(ne); }

 | expr AND expr { code(and); }

 | expr OR expr { code(or); }

 | NOT expr { $$ = $2; code(not); }

 ;

prlist: expr { code(prexpr); }

 | STRING { $$ = code2(prstr, (Inst)$1); }

 | prlist expr { code(prexpr); }

 | prlist STRING { code2(prstr, (Inst)$3); }

 ;

defn: FUNC procname { $2->type=FUNCTION; indef=1; }

 '(' ')' stmt { code(procret); define($2); indef=0; }

 | PROC procname { $2->type=PROCEDURE; indef=1; }

 '(' ')' stmt { code(procret); define($2); indef=0; }

 ;

procname: VAR