UNIX

  scanf("%lf", &d);

  yylval.sym = install("", NUMBER, d);

  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;

 }

 switch (c) {

 case '>': return follow('=', GE, GT);

 case '<': return follow('=', LE, LT);

 case '=': return follow('=', EQ, '=');

 case '!': return follow('=', NE, NOT);

 case '|': return follow('|', OR, '|');

 case '&': return follow('&', AND, '&');

 case '\n': lineno++; return '\n';

 default: return c;

 }

}

follow(expect, ifyes, ifno) /* look ahead for >=, etc. */

{

 int c = getchar();

 if (c == expect)

  return ifyes;

 ungetc(c, stdin);

 return ifno;

}

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);

}

main(argc, argv)

 char *argv[];

{

 int fpecatch();

 progname = argv[0];

 init();

 setjmp(begin);

 signal(SIGFPE, fpecatch);

 for (initcode(); yyparse(); initcode())

  execute(prog);

 return 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);

 while (c != '\n' && с != EOF)

  c = getchar(); /* flush rest of input line */

 fseek(stdin, 0L, 2); /* flush rest of file */

 longjmp(begin, 0);

}

3.6.6 init.c

#include "hoc.h"

#include "y.tab.h"

#include

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

static struct { /* Keywords */

 char *name;

 int kval;

} keywords[] = {

 "if",    IF,

 "else",  ELSE,

 "while", WHILE,

 "print", PRINT,

 0,       0,

};

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,

 "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; keywords[i].name; i++)

  install(keywords[i].name, keywords[i].kval, 0.0);

 for (i = 0; consts[i].name; i++)

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