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hoc4

3.5.1 code.c

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

#define NSTACK 256
static Datum stack[NSTACK]; /* the stack */
static Datum *stackp; /* next free spot on stack */

#define NPROG 2000
Inst prog[NPROG]; /* the machine */
Inst *progp; /* next free spot for code generation */
Inst *pc; /* program counter during execution */

initcode() /* initialize for code generation */
{
 stackp = stack;
 progp = prog;
}

push(d) /* push d onto stack */
 Datum d;
{
 if (stackp >= &stack[NSTACK])
  execerror("stack overflow", (char*)0);
 *stackp++ = d;
}

Datum pop() /* pop and return top elem from stack */
{
 if (stackp <= stack)
  execerror("stack underflow", (char*)0);
 return *--stackp;
}

constpush() /* push constant onto stack */
{
 Datum d;
 d.val = ((Symbol*)*pc++)->u.val;
 push(d);
}

varpush() /* push variable onto stack */
{
 Datum d;
 d.sym = (Symbol*)(*pc++);
 push(d);
}

bltin() /* evaluate built-in on top of stack */
{
 Datum d;
 d = pop();
 d.val = (*(double(*)())(*pc++))(d.val);
 push(d);
}

eval() /* evaluate variable on stack */
{
 Datum d;
 d = pop() ;
 if (d.sym->type == UNDEF)
  execerror("undefined variable", d.sym->name);
 d.val = d.sym->u.val;
 push(d);
}

add() /* add top two elems on stack */
{
 Datum d1, d2;
 d2 = pop();
 d1 = pop();
 d1.val += d2.val;
 push(d1);
}

sub() /* subtract top of stack from next */
{
 Datum d1, d2;
 d2 = pop();
 d1 = pop();
 d1.val -= d2.val;
 push(d1);
}

mul() {
 Datum d1, d2;
 d2 = pop();
 d1 = pop();
 d1.val *= d2.val;
 push(d1);
}

div() {
 Datum d1, d2;
 d2 = pop();
 if (d2.val == 0.0)
  execerror("division by zero", (char*)0);
 d1 = pop();
 d1.val /= d2.val;
 push(d1);
}

negate() {
 Datum d;
 d = pop();
 d.val = -d.val;
 push(d);
}

power() {
 Datum d1, d2;
 extern double Pow();
 d2 = pop();
 d1 = pop();
 d1.val = Pow(d1.val, d2.val);
 push(d1);
}

assign() /* assign top value to next value */
{
 Datum d1, d2;
 d1= pop();
 d2 = pop();
 if (d1.sym->type != VAR && d1.sym->type != UNDEF)
  execerror("assignment to non-variable", d1.sym->name);
 d1.sym->u.val = d2.val;
 d1.sym->type = VAR;
 push(d2);
}

print() /* pop top value from stack, print it */
{
 Datum d;
 d = pop();
 printf("\t%8g\n", d.val);
}

Inst *code(f) /* install one instruction or operand */
 Inst f;
{
 Inst *oprogp = progp;
 if (progp >= &eprog[NPROG])
  execerror("program too big", (char*)0);
 *progp++ = f;
 return oprogp;
}

execute(p) /* run the machine */
 Inst *p;
{
 for (pc = p; *pc != STOP; )
  (*(*pc++))();
}

3.5.2 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();

typedef union Datum { /* interpreter stack type */
 double val;
 Symbol *sym;
} Datum;
extern Datum pop();

typedef int (*Inst)(); /* machine instruction */
#define STOP (Inst)0
extern Inst prog[];
extern eval(), add(), sub(), mul(), div(), negate(), power();
extern assign(), bltin(), varpush(), constpush(), print();

3.5.3 hoc.y

%{
#include "hoc.h"
#define code2(c1,c2) code(c1); code(c2)
#define code3(c1,c2,c3) code(c1); code(c2); code(c3)
%}
%union {
 Symbol *sym; /* symbol table pointer */
 Inst *inst; /* machine instruction */
}
%token  NUMBER VAR BLTIN UNDEF
%right '='
%left '+' '-'
%left '*' '/'
%left UNARYMINUS
%right '^' /* exponentiation */
%%
list: /* nothing */
 | list '\n'
 | list asgn '\n' { code2(pop, STOP); return 1; }
 | list expr '\n' { code2(print, STOP); return 1; }
 | list error '\n' { yyerrok; }
 ;
asgn: VAR '=' expr { code3(varpush,(Inst)$1.assign); }
 ;
expr: NUMBER { code2(constpush, (Inst)$1); }
 | VAR { code3(varpush, (Inst)$1, eval); }
 | asgn
 | BLTIN '(' expr ')' { code2(bltin, (Inst)$1->u.ptr); }
 | '(' expr ')'
 | expr '+' expr { code(add); }
 | expr '-' expr { code(sub); }
 | expr '*' expr { code(mul); }
 | expr '/' expr { code(div); }
 | expr '^' expr { code(power); }
 | '-' expr %prec UNARYMINUS { code(negate); }
 ;
%%
/* end of grammar */
#include 
#include 
char *progname;
int lineno = 1;
#include 
#include 
jmp_buf begin;

main(argc, argv) /* hoc4 */
 char *argv[];
{
 int fpecatch();
 progname = argv[0];
 init();
 setjmp(begin);
 signal(SIGFPE, fpecatch);
 for (initcode(); yyparse(); initcode())
  execute(prog);
 return 0;
}

static int c; /* global for use by warning() */

yylex() /* hoc4 */
{
 while ((c=getchar()) == ' ' || с == '\t')
  ;
 if (c == EOF)
  return 0;
 if (c == '.' || isdigit(c)) { /* number */
  double d;
  ungetc(c, stdin);
  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;
 }
 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);
 while (c != '\n' && с != EOF)
  с = getchar(); /* flush rest of input line */
}

3.5.4 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;
 }
}

3.5.5. makefile

YFLAGS = -d
OBJS = hoc.o code.o init.o math.o symbol.o

hoc4: $(OBJS)
      cc $(OBJS) -lm -o hoc4

hoc.o code.o init.o symbol.o: hoc.h

code.o init.o symbol.o: x.tab.h

x.tab.h: y.tab.h
      -cmp -s x.tab.h y.tab.h || cp y.tab.h x.tab.h

pr: hoc.y hoc.h code.c init.c math.c symbol.c
      @pr $?
      @touch pr

clean:
      rm -f $(OBJS) [xy].tab.[ch]

3.5.6. 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;
}

3.5.7 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;
}

3.6