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|
%{
double mem[26];
%}
%union {
double val;
int idx;
}
%token <val> NUMBER
%token <idx> VAR
%type <val> expr
%right '='
%left '+' '-'
%left '*' '/'
%left UNMIN
%%
list: /* ε */
| list '\n'
| list expr '\n' { print("\t%.8g\n", $2); }
| list expr ';' { print("\t%.8g\n", $2); }
| list error '\n' { yyerrok; }
;
expr: NUMBER
| VAR { $$ = mem[$1]; }
| VAR '=' expr { $$ = mem[$1] = $3; }
| '-' expr %prec UNMIN { $$ = -$2; }
| expr '+' expr { $$ = $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 ')' { $$ = $1 * $3; }
| '(' expr ')' { $$ = $2; }
;
%%
#include <u.h>
#include <libc.h>
#include <ctype.h>
#include <bio.h>
Biobuf *bin;
jmp_buf begin;
int lineno;
int prompt;
int yyparse(void);
void
error(char *msg, int ln)
{
fprint(2, "%s at line %d\n", msg, ln);
}
void
yyerror(char *msg)
{
error(msg, lineno);
}
int
yylex(void)
{
int c;
if(prompt){
print("%d: ", lineno);
prompt--;
}
while((c = Bgetc(bin)) == ' ' || c == '\t')
;
if(c == '.' || isdigit(c)){
Bungetc(bin);
Bgetd(bin, &yylval.val);
return NUMBER;
}
if(islower(c)){
yylval.idx = c - 'a';
return VAR;
}
if(c == '\n'){
lineno++;
prompt++;
}
return c;
}
void
rterror(char *msg)
{
error(msg, lineno-1);
longjmp(begin, 0);
}
int
catch(void *ureg, char *msg)
{
if(strncmp(msg, "sys: fp", 7) == 0){
error("floating point exception", lineno-1);
notejmp(ureg, begin, 0);
}
return 0;
}
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();
bin = Bfdopen(0, OREAD);
if(bin == nil)
sysfatal("Bfdopen: %r");
lineno++;
prompt++;
setjmp(begin);
atnotify(catch, 1);
yyparse();
Bterm(bin);
exits(0);
}
|
