Брайан Керниган - UNIX — универсальная среда программирования

execerror("division by zero", "");

$$ = $1 / $3;

}

| '(' expr ')' { $$ = $2; }

| '-' expr %prec UNARYMINUS { $$ = -$2; }

;

%%

/* end of grammar */

#include

#include

char *progname;

int lineno = 1;

#include

#include

jmp_buf begin;

main(argc, argv) /* hoc2 */

char *argv[];

{

int fpecatch();

progname = argv[0];

setjmp(begin);

signal(SIGFPE, fpecatch);

yyparse();

}

yylex() /* hoc2 */

{

int c;

while ((c=getchar()) == ' ' || c == '\t')

;

if (c == EOF)

return 0;

if (c == '.' || isdigit(c)) { /* number */

ungetc(c, stdin);

scanf("%lf", &yylval.val);

return NUMBER;

}

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);

}

hoc2: hoc.o

cc hoc.o -o hoc2

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]

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();

%{

#include "hoc.h"

extern double Pow();

%}

%union {

double val; /* actual value */

Symbol *sym; /* symbol table pointer */

}

%token NUMBER

%token VAR BLTIN UNDEF

%type 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); }

| expr '+' expr { $$ = $1 + $3; }

| expr '-' expr { $$ = $1 - $3; }

| expr '*' expr { $$ = $1 * $3; }

| expr '/' expr {

if ($3 == 0.0)

execerror("division by zero", "");

$$ = $1 / $3;

}

| expr '^' expr { $$ = Pow($1, $3); }

| '(' expr ')' { $$ = $2; }

| '-' expr %prec UNARYMINUS { $$ = -$2; }

;

%%

/* end of grammar */

#include

#include

char *progname;

int lineno = 1;

#include

#include

jmp_buf begin;

main(argc, argv) /* hoc3 */

char *argv[];

{

int fpecatch();

progname = argv[0];

init();

setjmp(begin);

signal(SIGFPE, fpecatch);

yyparse();

}

yylex() /* hoc3 */

{

int c;

while ((c=getchar()) == ' ' || c == '\t')

;

if (c == EOF)

return 0;

if (c == '.' || isdigit(c)) {

/* number */

ungetc(c, stdin);

scanf("%lf", &yylval.val);

return NUMBER;

}

if (isalpha(c)) {

Symbol *s;

char sbuf[100], *p = sbuf;

do {

*p++ = c;

} while ((c=getchar()) != EOF && isalnum(c));

ungetc(c, stdin);

*p = '\0';

if ((s=lookup(sbuf)) == 0)

s = install(sbuf, UNDEF, 0.0);

yylval.sym = s;

return s->type == UNDEF ? VAR : s->type;

}

if (c == '\n')

lineno++;

return c;

}

yyerror(s)

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)

char *s, *t;

{

fprintf(stderr, "%s: %s", progname, s);

if (t && *t)

fprintf (stderr, " %s", t);

fprintf(stderr, " near line %d\n", lineno);

}

#include "hoc.h"

#include "y.tab.h"