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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  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);
}

3.3.4 init.c

#include "hoc.h"
#include "y.tab.h"
#include 

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++) {
  s = install(builtins[i].name, BLTIN, 0.0);
  s->u.ptr = builtins[i].func;
 }
}

3.3.5 math.c

#include 
#include 
extern int errno;

double errcheck();

double Log(x)
 double x;
{
 return errcheck(log(x), "log");
}

double Log10(x)
 double x;
{
 return errcheck(log10(x), "log10");
}

double Sqrt(x)
 double x;
{
 return errcheck(sqrt(x), "sqrt");
}

double Exp(x)
 double x;
{
 return errcheck(exp(x), "exp");
}

double Pow(x, y)
 double x, y;
 return errcheck(pow(x,y), "exponentiation");
}

double integer(x)
 double x;
{
 return (double)(long)x;
}

double errcheck(d, s) /* check result of library call */
 double d;
 char *s;
{
 if (errno == EDOM) {
  errno = 0;
  execerror(s, "argument out of domain");
 }
 else if (errno == ERANGE) {
  errno = 0;
  execerror(s, "result out of range");
 }
 return d;
}

3.3.6 symbol.c

#include "hoc.h"
#include "y.tab.h"

static Symbol *symlist = 0; /* symbol table: linked list */

Symbol *lookup(s) /* find s in symbol table */
 char *s;
{
 Symbol *sp;

 for (sp = symlist; sp != (Symbol*)0; sp = sp->next)
  if (strcmp(sp->name, s) == 0)
   return sp;
 return 0; /* 0 ==> not found */
}

Symbol *install(s, t, d) /* install s in symbol table */
 char *s;
 int t;
 double d;
 Symbol *sp;
 char *emalloc();

 sp = (Symbol*)emalloc(sizeof(Symbol));
 sp->name = emalloc(strlen(s)+1); /* +1 for '\0' */
 strcpy(sp->name, s);
 sp->type = t;
 sp->u.val = d;
 sp->next = symlist; /* put at front of list */
 symlist = sp;
 return sp;
}

char *emalloc(n) /* check return from malloc */
 unsigned n;
{
 char *p, *malloc();

 p = malloc(n);
 if (p == 0)
  execerror("out of memory", (char*)0);
 return p;
}

3.4