UNIX — универсальная среда программирования

 | 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 stdio.h

#include ctype.h

char *progname;

int lineno = 1;

#include signal.h

#include setjmp.h

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);

}

3.3.4 init.c

#include "hoc.h"

#include "y.tab.h"

#include math.h

extern double Log, Log10, Exp, Sqrt, integer;

static struct { /* Constants */

 char *name;

 double eval;

} consts[] = {

 "PI",    3.14159265358979323846,

 "E",     2.71828182845904523536,

 "GAMMA", 0.57721566490153286060, /* Euler */

 "DEG",  57.29577951308232087680, /* deg/radian */

 "PHI",   1.61803398874989484820, /* golden ratio */

 0, 0

};

static struct { /* Built-ins */

 char *name;

 double (*func);

} builtins[] = {

 "sin",   sin,

 "cos",   cos,

 "atan",  atan,

 "log",   Log, /* checks argument */

 "log10", Log10, /* checks argument */

 "exp",   Exp, /* checks argument */

 "sqrt",  Sqrt, /* checks argument */

 "int",   integer,

 "abs",   fabs,

 0,       0

};

init /* install constants and built-ins in table */

{

 int i;

 Symbol *s;

 for (i = 0; consts[i].name; i++)

  install(consts[i].name, VAR, consts[i].eval);

 for (i = 0; builtins[i].name; i++) {