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|
%{
#include "dat.h"
%}
%union {
double val;
Symbol *sym;
}
%token <val> NUMBER
%token <sym> VAR CONST BLTIN UNDEF
%type <val> expr asgn
%right '='
%left '+' '-'
%left '*' '/'
%left '%'
%right '^'
%left UMINUS
%%
list: /* ε */
| list '\n'
| list asgn '\n'
| list expr '\n' { print("\t%.8g\n", $2); }
| list error '\n' { yyerrok; }
;
asgn: VAR '=' expr
{
if($1->type == CONST)
rterror("assignment to constant");
$$ = $1->u.val = $3;
$1->type = VAR;
}
;
expr: NUMBER
| VAR
{
if($1->type == UNDEF)
rterror("undefined variable");
$$ = $1->u.val;
}
| asgn
| BLTIN '(' expr ')' { $$ = $1->u.fn($3); }
| '-' expr %prec UMINUS { $$ = -$2; }
| expr '+' expr { $$ = $1 + $3; }
| expr '-' expr { $$ = $1 - $3; }
| expr '*' expr { $$ = $1 * $3; }
| expr '/' expr
{
if($3 == 0)
rterror("division by zero");
$$ = $1 / $3;
}
| expr '%' expr { $$ = fmod($1, $3); }
| expr '^' expr { $$ = pow($1, $3); }
| expr '(' expr ')' { $$ = $1 * $3; }
| '(' expr ')' { $$ = $2; }
;
%%
#include <u.h>
#include <libc.h>
#include <ctype.h>
#include <bio.h>
#include "fns.h"
Biobuf *bin;
jmp_buf begin;
int lineno;
int prompt;
void *
emalloc(ulong n)
{
void *p;
p = malloc(n);
if(p == nil)
sysfatal("malloc: %r");
memset(p, 0, n);
setmalloctag(p, getcallerpc(&n));
return p;
}
void
yyerror(char *msg)
{
fprint(2, "%s at line %d\n", msg, lineno);
}
void
rterror(char *msg)
{
fprint(2, "%s at line %d\n", msg, lineno-1);
longjmp(begin, 0);
}
int
catch(void *ureg, char *msg)
{
if(strncmp(msg, "sys: fp", 7) == 0){
yyerror("floating point exception");
notejmp(ureg, begin, 0);
}
return 0;
}
int
yylex(void)
{
Symbol *s;
char sname[256], *p;
Rune r;
if(prompt){
print("%d: ", lineno);
prompt--;
}
while((r = Bgetrune(bin)) == ' ' || r == '\t')
;
if(r == Beof)
return 0;
if(r == '.' || isdigitrune(r)){
Bungetrune(bin);
Bgetd(bin, &yylval.val);
return NUMBER;
}
if(isalpharune(r)){
p = sname;
do{
if(p+runelen(r) - sname >= sizeof(sname))
return r; /* force syntax error. */
p += runetochar(p, &r);
}while((r = Bgetrune(bin)) != Beof &&
(isalpharune(r) || isdigitrune(r)));
Bungetrune(bin);
*p = 0;
if((s = lookup(sname)) == nil)
s = install(sname, UNDEF, 0);
yylval.sym = s;
return s->type == UNDEF || s->type == CONST ? VAR : s->type;
}
if(r == '\n'){
lineno++;
prompt++;
}
return r;
}
void
usage(void)
{
fprint(2, "usage: %s\n", argv0);
exits("usage");
}
void
main(int argc, char *argv[])
{
ARGBEGIN{
default: usage();
}ARGEND;
if(argc > 0)
usage();
atnotify(catch, 1);
bin = Bfdopen(0, OREAD);
if(bin == nil)
sysfatal("Bfdopen: %r");
lineno++;
prompt++;
init();
setjmp(begin);
yyparse();
Bterm(bin);
exits(0);
}
|
