UNIX — универсальная среда программирования - Керниган Брайан Уилсон
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61
ack(3,4)
hoc: стек слишком велик (строка 8)
...
• Формула Стирлинга:
$ hoc
func stirl() {
return sqrt(2 * $1 * PI) * ($1 / E) ^ $1 * (1 + 1 / (12 * $1))
}
stirl(10) 3628684.7
stirl(20) 2.4328818e+18
• Функция факториал n!
func fac() if ($1 <= 0) return 1 else return $1 * fac($1 - 1)
Отношение факториала к приближению Стирлинга:
i = 9
while ((i = i + 1) <= 20) {
print i, " ", fac(i)/stirl(i), "n"
}
10 1.0000318
11 1.0000265
12 1.0000224
13 1.0000192
14 1.0000166
15 1.0000146
16 1.0000128
17 1.0000114
18 1.0000102
19 1.0000092
20 1.0000083
Приложение 3
Исходные тексты калькулятора hoc
These files contain all the code from "The Unix Programming Environment", by Brian Kernighan and Rob Pike (Prentice Hall, 1984, ISBN 0-13-937681-X). A separate hoc6 distribution contains any fixes that we have applied to that; the version in this file is from the book.
Copyright © Lucent Technologies, 1997. All Rights Reserved
Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both the copyright notice and this permission notice and warranty disclaimer appear in supporting documentation, and that the name of Lucent Technologies or any of its entities not be used in advertising or publicity pertaining to distribution of the software without specific, written prior permission.
LUCENT TECHNOLOGIES DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL LUCENT OR ANY OF ITS ENTITIES BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
3.1 hoc1
3.1.1 makefile
hoc1: hoc.o
cc hoc.o -o hoc1
3.1.2 hoc.y
%{
#define YYSTYPE double /* data type of yacc stack */
%}
%token NUMBER
%left '+' /* left associative, same precedence */
%left '*' '/' /* left assoc., higher precedence */
%%
list : /* nothing */
| list 'n'
| list expr 'n' { printf("t%.8gn", $2); }
;
expr: NUMBER { $$ = $1; }
| expr '+' expr { $$ = $1 + $3; }
| expr '-' expr { $$ = $1 - $3; }
| expr '*' expr { $$ = $1 * $3; }
| expr '/' expr { $$ = $1 / $3; }
| '(' expr ')' { $$ = $2; }
;
%%
/* end of grammar */
#include <stdio.h>
#include <ctype.h>
char *progname; /* for error messages */
int lineno = 1;
main(argc, argv) /* hoc1 */
char *argv[];
{
progname = argv[0];
yyparse();
}
yylex() /* hoc1 */
{
int c;
while ((c=getchar()) == ' ' || c == 't')
;
if (c == EOF)
return 0;
if (c == '.' || isdigit(c)) { /* number */
ungetc(c, stdin);
scanf("%lf", &yylval);
return NUMBER;
if (c == 'n')
lineno++;
return c;
}
yyerror(s) /* called for yacc syntax error */
char *s;
{
warning(s, (char*)0);
}
warning(s, t) /* print warning message */
char *s, *t;
{
fprintf(stderr, "%s: %s", progname, s);
if (t)
fprintf(stderr, " %s", t);
fprintf(stderr, " near line %dn", lineno);
