Usenet 1994 January/usenetsourcesnewsgroupsinfomagicjanuary1994.iso/sources/unix/volume2/basic/part3/bs2/bsgram.y

Text File | 1986-11-30 | 6.6 KB | 348 lines

    /* bsgram.y -- grammer specification for bs.
     */
%{
#include "bsdefs.h"

char *p;        /* the generic pointer */
int i;            /* the generic counter */

struct stk {
    int stack[40];
    int stkp;
};

struct stk ifstk,whstk,forstk,repstk,lpstk;
int gomax=0; int ifmax=0; int whmax=0; int formax=0; int repmax=0; int lpmax=0;

extern char *yytext;
extern char *bsyysval;
extern int yyleng;
%}

%term EQUAL    NEQ    LE    LT    GE    WHILE
%term GT    OR    AND    NOT    RET    REPEAT
%term IF    THEN    ELSE    GOTO    GOSUB    UNTIL
%term STOP    END    INTEGER    REAL    SCONST    ELIHW
%term LET    SWORD    PRINT    INPUT    DATA    CFOR
%term FOR    TO    STEP    READ    WRITE    NEXT
%term DEFINE    LFUN    SFUN    FDEF    SYMBOL    DIM
%term VALUE    IWORD    RWORD    ROFC    LOOP    EXITIF
%term ITOR    RTOI    ITOA    RTOA    LEAVE    CONTINUE
%term POOL

%left ',' ';'
%right '='
%nonassoc OR AND
%nonassoc LE LT GE GT EQUAL NEQ
%left '+' '-'
%left '*' '/' '%'
%left UNARY
%left '('


%start lines

%%

lines        : /* empty */
        | lines line
        ;

line        : lnum stat '\n'
            { printf("\n"); }
        | '\n'
        ;

lnum        : INTEGER
            { printf(" line %s ",$1); }
        ;

stat        : LET let_xpr
        | let_xpr
        | PRINT pe
            { printf(" print "); }
        | GOTO INTEGER
            { printf(" rlabel LN%s goto ",$2); }
        | GOSUB INTEGER
            { printf(" rlabel LN%s gosub ",$2); }
        | LEAVE
            { printf(" leave "); }
        | CONTINUE
            { printf(" contin "); }
        | RET
            { printf(" return "); }
        | IF bexpr
            {
                lpush(&ifstk,ifmax);
                printf(" rlabel IF%d if ",ifmax);
                ifmax += 2;
            }
          THEN stat
            {
                i = ltop(&ifstk);
                printf(" rlabel IF%d goto ",i+1);
            }
          if_else
        | INPUT
            { printf(" pushstate %d ",M_INPUT); }
          var_lst
            { printf(" popstate "); }
        | STOP
            { printf(" stop "); }
        | END
            { printf(" end "); }
        | FOR ivar '=' rexpr TO rexpr for_step
            {
                lpush(&forstk,formax);
                printf(" rlabel FOR%d rlabel FOR%d enter",
                    formax+2,formax+1);
                printf(" icon 0 rlabel FOR%d dlabel FOR%d for ",
                    formax+1,formax);
                formax += 3;
            }
        | NEXT
            {
                i = ltop(&forstk);
                printf(" dlabel FOR%d ",i+2);
            }
          ivar
            {
                i = lpop(&forstk);
                printf(" next rlabel FOR%d goto dlabel FOR%d ",
                    i,i+1);
                printf("exitlp ");
            }
        | READ { printf(" pushstate %d ",M_READ); } var_lst
            { printf(" popstate "); }
        | DATA { printf(" data "); } data_lst
        | LOOP
            {
                lpush(&lpstk,lpmax);
                printf(" rlabel LP%d rlabel LP%d enter",
                    lpmax+2,lpmax+1);
                printf(" dlabel LP%d ",lpmax);
                lpmax += 3;
            }
        | EXITIF bexpr
            {
                i = ltop(&lpstk);
                printf(" not rlabel LP%d if ",i+1);
            }
        | POOL
            {
                i = lpop(&lpstk);
                printf(" dlabel LP%d rlabel LP%d goto",i+2,i);
                printf(" dlabel LP%d exitlp ",i+1);
            }
        | WHILE
            {
                lpush(&whstk,whmax);
                printf(" rlabel WH%d rlabel WH%d enter",
                    whmax+2,whmax+1);
                printf(" dlabel WH%d ",whmax);
                whmax += 3;
            }
          bexpr
            {
                i = ltop(&whstk);
                printf(" rlabel WH%d if ",i+1);
            }
        | ELIHW
            {
                i = lpop(&whstk);
                printf(" dlabel WH%d",i+2);
                printf(" rlabel WH%d goto dlabel WH%d exitlp ",i,i+1);
            }
        | REPEAT
            {
                lpush(&repstk,repmax);
                printf(" rlabel REP%d rlabel REP%d enter",
                    repmax+1,repmax+2);
                printf(" dlabel REP%d ",repmax);
                repmax += 3;
            }
        | UNTIL
            {
                i = ltop(&repstk);
                printf(" dlabel REP%d ",i+1);
            }
          bexpr
            {
                i = lpop(&repstk);
                printf(" not rlabel REP%d if",i);
                printf(" dlabel REP%d exitlp ",i+2);
            }
        ;

let_xpr        : ivar '=' rexpr
            { printf(" rtoi store %d pop ",T_INT); }
        | rvar '=' rexpr
            { printf(" store %d pop ",T_DBL); }
        | svar '=' sexpr
            { printf(" store %d spop ",T_CHR); }
        ;

data_lst    : rexpr
            { printf(" dsep "); }
        | sexpr
            { printf(" dsep "); }
        | data_lst ',' rexpr
            { printf(" dsep "); }
        | data_lst ',' sexpr
            { printf(" dsep "); }
        ;

ind_lst        : rexpr
        | ind_lst ',' rexpr
        ;

for_step    : /* empty */
            { printf(" icon 0 "); }
        | STEP rexpr
        ;

if_else        : /* empty */
            {
                i = lpop(&ifstk);
                printf(" dlabel IF%d dlabel IF%d ",i,i+1);
            }
        | ELSE { i=ltop(&ifstk); printf(" dlabel IF%d ",i); } stat
            { i=lpop(&ifstk); printf(" dlabel IF%d ",i+1); }
        ;


pe        : sexpr ','
            { printf(" scon \"\" , "); }
        | sexpr ';'
        | sexpr
            { printf(" scon \"\\n\" ; "); }
        | /* empty */
            { printf(" scon \"\\n\" "); }
        ;


var_lst        : ivar
        | rvar
        | svar
        | var_lst ',' var_lst
        ;

sexpr        : SCONST
            { printf(" scon \"%s\" ",$1); }
        | svar
            { printf(" val %d ",T_CHR); }
        | rexpr
            { printf(" rtoa "); }
        | svar '=' sexpr
            { printf(" store %d ",T_CHR); }
        | sexpr ';' sexpr
            { printf(" ; "); }
        | sexpr '+' sexpr
            { printf(" ; "); }
        | sexpr ',' sexpr
            { printf(" , "); }
        | '(' sexpr ')'
        ;
sbe        : sexpr EQUAL sexpr
            { printf(" s== "); }
        | sexpr NEQ sexpr
            { printf(" s<> "); }
        | sexpr LE sexpr
            { printf(" s<= "); }
        | sexpr LT sexpr
            { printf(" s< "); }
        | sexpr GE sexpr
            { printf(" s>= "); }
        | sexpr GT sexpr
            { printf(" s> "); }
        ;

ivar        : IWORD
            { printf(" var %d %s ",T_INT,$1); }
        | IWORD '(' {printf(" pushstate %d ",M_EXECUTE); } ind_lst ')'
            { printf(" popstate var %d %s ",T_INT+Q_ARY,$1); }
        ;
rvar        : RWORD
            { printf(" var %d %s ",T_DBL,$1); }
        | RWORD '(' { printf(" pushstate %d ",M_EXECUTE); } ind_lst ')'
            { printf(" popstate var %d %s ",T_DBL+Q_ARY,$1); }
        ;

svar        : SWORD
            { printf(" var %d %s ",T_CHR,$1); }
        | SWORD '(' { printf(" pushstate %d ",M_EXECUTE); } ind_lst ')'
            { printf(" popstate var %d %s ",T_CHR+Q_ARY,$1); }
        ;



rexpr        : rvar
            { printf(" val %d ",T_DBL); }
        | REAL
            { printf(" rcon %s ",$1); }
        | INTEGER
            { printf(" rcon %s ",$1); }
        | ivar
            { printf(" val %ditor ",T_INT); }
        | rvar '=' rexpr
            { printf(" store %d ",T_DBL); }
        | '(' rexpr ')'
        | rexpr '+' rexpr
            { printf(" r+ "); }
        | rexpr '-' rexpr
            { printf(" r- "); }
        | rexpr '*' rexpr
            { printf(" r* "); }
        | rexpr '/' rexpr
            { printf(" r/ "); }
        | '+' rexpr    %prec UNARY
        | '-' rexpr    %prec UNARY
            { printf(" rcon -1 r* "); }
        ;

rbe        : rexpr EQUAL rexpr
            { printf(" r== "); }
        | rexpr NEQ rexpr
            { printf(" r<> "); }
        | rexpr LE rexpr
            { printf(" r<= "); }
        | rexpr LT rexpr
            { printf(" r< "); }
        | rexpr GE rexpr
            { printf(" r>= "); }
        | rexpr GT rexpr
            { printf(" r> "); }
        ;
bexpr        : sbe
        | rbe
        | NOT bexpr    %prec UNARY
            { printf(" not "); }
        | bexpr OR bexpr
            { printf(" or "); }
        | bexpr AND bexpr
            { printf(" and "); }
        | '(' bexpr ')'
        ;
%%

main()
{
    rdlin(bsin);
    return(yyparse());
}

yyerror(s)
char *s;
{
    fprintf(stderr,"%s\n",s);
}

lpush(stack,val) struct stk *stack; int val;
{ stack->stack[stack->stkp++] = val; }

int ltop(stack) struct stk *stack;
{ return(stack->stack[stack->stkp-1]); }

int lpop(stack) struct stk *stack;
{ return(stack->stack[--stack->stkp]); }