Шрифт:
}
if (islower(c)) {
yylval.index = c - 'a'; /* ASCII only */
return VAR;
}
if (c == '\n')
lineno++;
return c;
}
yyerror(s) /* report compile-time error */
char *s;
{
warning(s, (char*)0);
}
execerror(s, t) /* recover from run-time error */
char *s, *t;
{
warning(s, t);
longjmp(begin, 0);
}
fpecatch /* catch floating point exceptions */
{
execerror("floating point exception", (char*)0);
}
warning(s, t) /* print warning message */
char *s, *t;
{
fprintf(stderr. "%s: %s", progname, s);
if (t && *t)
fprintf(stderr, " %s , t);
fprintf(stderr, " near line %d\n", lineno);
}
3.2.2
makefile
hoc2: hoc.o
cc hoc.o -o hoc2
3.3
hoc3
3.3.1
makefile
YFLAGS = -d # force creation of y.tab.h
OBJS = hoc.o init.o math.o symbol.o # abbreviation
hoc3: $(OBJS)
cc $(OBJS) -lm -o hoc3
hoc.o: hoc.h
init.o symbol.o: hoc.h y.tab.h
pr:
@pr hoc.y hoc.h init.c math.c symbol.c makefile
clean:
rm -f $(OBJS) y.tab.[ch]
3.3.2
hoc.h
typedef struct Symbol { /* symbol table entry */
char *name;
short type; /* VAR, BLTIN, UNDEF */
union {
double val; /* if VAR */
double (*ptr); /* if BLTIN */
} u;
struct Symbol *next; /* to link to another */
} Symbol;
Symbol *install, *lookup;
3.3.3
hoc.y
%{
#include "hoc.h"
extern double Pow;
%}
%union {
double val; /* actual value */
Symbol *sym; /* symbol table pointer */
}
%token <val> NUMBER
%token <sym> VAR BLTIN UNDEF
%type <val> expr asgn
%right '=' %left '+' '-'
%left '*' '/'
%left UNARYMINUS
%right /* exponentiation */
%%
list: /* nothing */
| list '\n'
| list asgn '\n'
| list expr '\n' { printf("\t%.8g\n", $2); }
| list error '\n' { yyerrok; }
;
asgn: VAR '=' expr { $$=$1->u.val=$3; $1->type = VAR; }
;
expr: NUMBER
| VAR { if ($l->type == UNDEF)
execerror("undefined variable", $1->name);
$$ = $1->u.val;
}
| asgn
| BLTIN '(' expr ')' { $$ = (*($1->u.ptr))($3); }