yap-6.3/packages/PLStream/pl-write.c

/*  $Id$

    Part of SWI-Prolog

    Author:        Jan Wielemaker
    E-mail:        J.Wielemaker@cs.vu.nl
    WWW:           http://www.swi-prolog.org
    Copyright (C): 1985-2010, University of Amsterdam
			      Vu University Amsterdam

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#include <math.h>
#include "pl-incl.h"
#include "pl-dtoa.h"
#include "pl-ctype.h"
#include <stdio.h>			/* sprintf() */
#ifdef HAVE_LOCALE_H
#include <locale.h>
#endif
#ifdef HAVE_FLOAT_H
#include <float.h>
#endif
#ifdef HAVE_IEEEFP_H
#include <ieeefp.h>
#endif

#ifdef fpclassify
#define HAVE_FPCLASSIFY 1
#endif

typedef struct visited
{ Word address;				/* we have done this address */
  struct visited *next;			/* next already visited */
} visited;

typedef struct
{ int   flags;				/* PL_WRT_* flags */
  int   max_depth;			/* depth limit */
  int   depth;				/* current depth */
  atom_t spacing;			/* Where to insert spaces */
  Module module;			/* Module for operators */
  IOSTREAM *out;			/* stream to write to */
  visited *visited;			/* visited (attributed-) variables */
} write_options;

static bool	writeTerm2(term_t term, int prec,
			   write_options *options, bool arg) WUNUSED;
static bool	writeTerm(term_t t, int prec,
			  write_options *options) WUNUSED;
static bool	writeArgTerm(term_t t, int prec,
			     write_options *options, bool arg) WUNUSED;

#if __YAP_PROLOG__
static Word
address_of(term_t t)
{ GET_LD
    return YAP_AddressFromSlot(t);			/* non-recursive structure */
}
#else
static Word
address_of(term_t t)
{ GET_LD
  Word adr = valTermRef(t);

  deRef(adr);
  switch(tag(*adr))
  { case TAG_ATTVAR:
      return adr;
    case TAG_COMPOUND:
      return valPtr(*adr);
    default:
      return NULL;			/* non-recursive structure */
  }
}
#endif


static int
has_visited(visited *v, Word addr)
{ for( ; v; v=v->next )
  { if ( v->address == addr )
      succeed;
  }

  fail;
}


char *
varName(term_t t, char *name)
#if __YAP_PROLOG__
{ 
  YAP_Int adr = YAP_VarSlotToNumber(t);

  if (adr < 0)
    Ssprintf(name, "_L%ld", -adr);
  else
    Ssprintf(name, "_G%ld", adr);

  return name;
}
#else
{ GET_LD
  Word adr = valTermRef(t);

  deRef(adr);

  if (adr > (Word) lBase)
    Ssprintf(name, "_L%ld", (Word)adr - (Word)lBase);
  else
    Ssprintf(name, "_G%ld", (Word)adr - (Word)gBase);

  return name;
}
#endif


#define AT_LOWER	0
#define AT_QUOTE	1
#define AT_FULLSTOP	2
#define AT_SYMBOL	3
#define AT_SOLO		4
#define AT_SPECIAL	5

/* Note: this only deals with ISO Latin-1 atoms; wide atoms are handled
   by writeUCSAtom()
*/

static int
atomType(atom_t a, IOSTREAM *fd)
{ Atom atom = atomValue(a);
  char *s = atomName(atom);
  size_t len = atomLength(atom);

  if ( len == 0 )
    return AT_QUOTE;

  if ( isLower(*s) )
  { for(++s; --len > 0 && isAlpha(*s) && Scanrepresent(*s, fd)==0; s++)
      ;
    return len == 0 ? AT_LOWER : AT_QUOTE;
  }

  if ( a == ATOM_dot )
    return AT_FULLSTOP;

  if ( isSymbol(*s) )
  { if ( len >= 2 && s[0] == '/' && s[1] == '*' )
      return AT_QUOTE;

    for(++s; --len > 0 && isSymbol(*s) && Scanrepresent(*s, fd)==0; s++)
      ;

    return len == 0 ? AT_SYMBOL : AT_QUOTE;
  }

					/* % should be quoted! */
  if ( len == 1 && *s != '%' )
  { if ( isSolo(*s) )
      return AT_SOLO;
  }

  if ( a == ATOM_nil || a == ATOM_curl )
    return AT_SPECIAL;

  return AT_QUOTE;
}


		 /*******************************
		 *	 PRIMITIVE WRITES	*
		 *******************************/

#define TRUE_WITH_SPACE 2		/* OK, and emitted leading space before token */

static bool
Putc(int c, IOSTREAM *s)
{ return Sputcode(c, s) == EOF ? FALSE : TRUE;
}


static bool
PutString(const char *str, IOSTREAM *s)
{ const unsigned char *q = (const unsigned char *)str;

  for( ; *q != EOS; q++ )
  { if ( Sputcode(*q, s) == EOF )
      return FALSE;
  }

  return TRUE;
}


static bool
PutComma(write_options *options)
{ if ( options->spacing == ATOM_next_argument )
    return PutString(", ", options->out);
  else
    return PutString(",", options->out);
}


static bool
PutStringN(const char *str, size_t length, IOSTREAM *s)
{ size_t i;
  const unsigned char *q = (const unsigned char *)str;

  for(i=0; i<length; i++, q++)
  { if ( Sputcode(*q, s) == EOF )
      return FALSE;
  }

  return TRUE;
}


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
PutOpenToken() inserts a space in the output stream if the last-written
and given character require a space to ensure a token-break.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

static bool
needSpace(int c, IOSTREAM *s)
{ if ( c == EOF )
  { s->lastc = EOF;
    return FALSE;
  } else if ( s->lastc != EOF &&
	      ((isAlphaW(s->lastc) && isAlphaW(c)) ||
	       (isSymbolW(s->lastc) && isSymbolW(c)) ||
	       (s->lastc != '(' && !isBlank(s->lastc) && c == '(') ||
	       (c == '\'' && isDigit(s->lastc))) )
  { return TRUE;
  }

  return FALSE;
}


static int
PutOpenToken(int c, IOSTREAM *s)
{ if ( needSpace(c, s) )
  { TRY(Putc(' ', s));
    return TRUE_WITH_SPACE;
  }

  return TRUE;
}


static int
PutToken(const char *s, IOSTREAM *stream)
{ if ( s[0] )
  { int rc;

    TRY(rc=PutOpenToken(s[0]&0xff, stream));
    TRY(PutString(s, stream));

    return rc;
  }

  return TRUE;
}


static int
PutTokenN(const char *s, size_t len, IOSTREAM *stream)
{ if ( len > 0 )
  { int rc;

    TRY(rc=PutOpenToken(s[0]&0xff, stream));
    TRY(PutStringN(s, len, stream));

    return rc;
  }

  return TRUE;
}


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
PutOpenBrace()/PutCloseBrace() are used to put  additional braces around
a term to avoid an operator  precedence   problem.  If  the last emitted
character  is  alphanumerical,  there  should  be  a  space  before  the
openbrace to avoid interpretation as a term.   E.g. not (a,b) instead of
not(a,b).  Reported by Stefan.Mueller@dfki.de.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

static int
PutOpenBrace(IOSTREAM *s)
{ int rc;

  TRY(rc=PutOpenToken('(', s));
  TRY(Putc('(', s));

  return rc;
}


static bool
PutCloseBrace(IOSTREAM *s)
{ return Putc(')', s);
}


static bool
putQuoted(int c, int quote, int flags, IOSTREAM *stream)
{ if ( (flags & PL_WRT_CHARESCAPES) )
  { if ( !(c < 0xff && isControl(c)) && c != quote && c != '\\' )
    { TRY(Putc(c, stream));
    } else
    { char esc[8];

      esc[1] = EOS;

      if ( c == quote )
      { esc[0] = c;
      } else
      { switch(c)
	{ case 7:
	    esc[0] = 'a';
	    break;
	  case '\b':
	    esc[0] = 'b';
	    break;
	  case '\t':
	    esc[0] = 't';
	    break;
	  case '\n':
	    esc[0] = 'n';
	    break;
	  case 11:
	    esc[0] = 'v';
	    break;
	  case '\r':
	    esc[0] = 'r';
	    break;
	  case '\f':
	    esc[0] = 'f';
	    break;
	  case '\\':
	    esc[0] = '\\';
	    break;
	  default:
	    if ( c <= 0xff )
	      Ssprintf(esc, "%03o\\", c);
	    else
	      assert(0);			/* to be done */
	}
      }
      if ( !Putc('\\', stream) ||
	   !PutString(esc, stream) )
	fail;
    }
  } else
  { if ( !Putc(c, stream) )
      fail;
    if ( c == quote || c == '\\' )	/* write '' or \\ */
    { if ( !Putc(c, stream) )
	fail;
    }
  }

  return TRUE;
}



static bool
writeQuoted(IOSTREAM *stream, const char *text, size_t len, int quote,
	    write_options *options)
{ const unsigned char *s = (const unsigned char *)text;

  TRY(Putc(quote, stream));

  while(len-- > 0)
  { TRY(putQuoted(*s++, quote, options->flags, stream));
  }

  return Putc(quote, stream);
}


#if O_ATTVAR
static bool
writeAttVar(term_t av, write_options *options)
{ GET_LD
  char buf[32];

  TRY(PutToken(varName(av, buf), options->out));

  if ( (options->flags & PL_WRT_ATTVAR_DOTS) )
  { return PutString("{...}", options->out);
  } else if ( (options->flags & PL_WRT_ATTVAR_WRITE) )
  { fid_t fid;
    term_t a;
    visited v;

    if ( !(fid = PL_open_foreign_frame()) )
      return FALSE;

    v.address = address_of(av);
    if ( has_visited(options->visited, v.address) )
      succeed;
    v.next = options->visited;
    options->visited = &v;
    Sputcode('{', options->out);
    a = PL_new_term_ref();
    PL_get_attr__LD(av, a PASS_LD);
    if ( !writeTerm(a, 1200, options) )
      goto error;
    Sputcode('}', options->out);
    PL_discard_foreign_frame(fid);

    options->visited = v.next;
    succeed;

  error:
    options->visited = v.next;
    fail;
  } else if ( (options->flags & PL_WRT_ATTVAR_PORTRAY) &&
	      GD->cleaning <= CLN_PROLOG )
  { fid_t fid;
    predicate_t pred;
    IOSTREAM *old;

    if ( !(fid = PL_open_foreign_frame()) )
      return FALSE;

    pred = _PL_predicate("portray_attvar", 1, "$attvar",
			 &GD->procedures.portray_attvar1);

    old = Scurout;
    Scurout = options->out;
    PL_call_predicate(NULL, PL_Q_NODEBUG, pred, av);
    Scurout = old;

    PL_discard_foreign_frame(fid);
  }

  succeed;
}
#endif


static bool
writeBlob(atom_t a, write_options *options)
{ Atom atom = atomValue(a);
  unsigned char const *s, *e;

  TRY(PutString("<#", options->out));
  s = (unsigned char const *)atomName(atom);
  for (e = s + atomLength(atom); s != e; s++)
  { static char *digits = "0123456789abcdef";

    TRY(Putc(digits[(*s >> 4) & 0xf], options->out));
    TRY(Putc(digits[(*s     ) & 0xf], options->out));
  }

  return PutString(">", options->out);
}


static int				/* FALSE, TRUE or TRUE_WITH_SPACE */
writeAtom(atom_t a, write_options *options)
{ Atom atom = atomValue(a);

  if ( (options->flags & PL_WRT_BLOB_PORTRAY) &&
       false(atomBlobType(atom), PL_BLOB_TEXT) &&
       GD->cleaning <= CLN_PROLOG )
  { GET_LD
    int rc;
    fid_t fid;
    predicate_t pred;
    IOSTREAM *old;
    term_t av;

    if ( !(fid = PL_open_foreign_frame()) )
      return FALSE;
    av = PL_new_term_ref();
    PL_put_atom(av, a);

    pred = _PL_predicate("portray", 1, "user",
			 &GD->procedures.portray);

    old = Scurout;
    Scurout = options->out;
    rc = PL_call_predicate(NULL, PL_Q_NODEBUG, pred, av);
    Scurout = old;

    PL_discard_foreign_frame(fid);
    if ( rc == TRUE )
      return TRUE;
  }

  if ( atomBlobType(atom)->write )
    return (*atomBlobType(atom)->write)(options->out, a, options->flags);
  if ( false(atomBlobType(atom), PL_BLOB_TEXT) )
    return writeBlob(a, options);

  if ( true(options, PL_WRT_QUOTED) )
  { switch( atomType(a, options->out) )
    { case AT_LOWER:
      case AT_SYMBOL:
      case AT_SOLO:
      case AT_SPECIAL:
	return PutToken(nameOfAtom(atom), options->out);
      case AT_QUOTE:
      case AT_FULLSTOP:
      default:
      { int rc;

	TRY(rc=PutOpenToken('\'', options->out));
	TRY(writeQuoted(options->out,
			nameOfAtom(atom),
			atomLength(atom),
			'\'', options));
	return rc;
      }
    }
  } else
    return PutTokenN(nameOfAtom(atom), atomLength(atom), options->out);
}


int
writeAtomToStream(IOSTREAM *s, atom_t atom)
{ write_options options;

  memset(&options, 0, sizeof(options));
  options.out = s;
  options.module = MODULE_user;

  return writeAtom(atom, &options);
}


int
writeUCSAtom(IOSTREAM *fd, atom_t atom, int flags)
{ Atom a = atomValue(atom);
  pl_wchar_t *s = (pl_wchar_t*)atomName(a);
  size_t len = atomLength(a)/sizeof(pl_wchar_t);
  pl_wchar_t *e = &s[len];

  if ( flags & PL_WRT_QUOTED )
  { pl_wchar_t quote = L'\'';
    int rc;

    if ( isLowerW(*s) )
    { pl_wchar_t *q;

      for(q=s; q<e; q++)
      { if ( !isAlphaW(*q) || Scanrepresent(*q, fd) < 0 )
	  break;
      }
      if ( q == e )
        goto unquoted;
    }

    TRY(Putc(quote, fd));

    while(s < e)
    { TRY(putQuoted(*s++, quote, flags, fd));
    }

    rc = Putc(quote, fd);

    return rc;
  }

unquoted:
  if ( s < e && !PutOpenToken(s[0], fd) )
    return FALSE;
  for( ; s<e; s++)
  { if ( !Putc(*s, fd) )
      return FALSE;
  }

  return TRUE;
}


#if O_STRING

static inline int
get_chr_from_text(const PL_chars_t *t, int index)
{ switch(t->encoding)
  { case ENC_ISO_LATIN_1:
      return t->text.t[index]&0xff;
    case ENC_WCHAR:
      return t->text.w[index];
    default:
      assert(0);
    return 0;
  }
}


static int
writeString(term_t t, write_options *options)
{ GET_LD
  PL_chars_t txt;

  PL_get_text(t, &txt, CVT_STRING);

  if ( true(options, PL_WRT_QUOTED) )
  { int quote;
    unsigned int i;

    if ( true(options, PL_WRT_BACKQUOTED_STRING) )
      quote = '`';
    else
      quote = '"';

    TRY(Putc(quote, options->out));

    for(i=0; i<txt.length; i++)
    { int chr = get_chr_from_text(&txt, i);

      TRY(putQuoted(chr, quote, options->flags, options->out));
    }

    return Putc(quote, options->out);
  } else
  { unsigned int i;

    for(i=0; i<txt.length; i++)
    { int chr = get_chr_from_text(&txt, i);

      TRY(Putc(chr, options->out));
    }
  }

  succeed;
}

#endif /*O_STRING*/


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Formatting a float. This used  to  use   sprintf(),  but  there  are two
problems with this. First of all, this uses the current locale, which is
complicated to avoid. Second, it does not provide a mode that guarantees
reliable read-back. Using %g gets closest,   but %.15g doesn't guarantee
read-back and %.17g does, but prints 0.1 as 0.100..001, etc.

This uses dtoa.c. See pl-dtoa.c for how this is packed into SWI-Prolog.

TBD: The number of cases are large. We should see whether it is possible
to clean this up a bit. The 5 cases   as  such are real: there is no way
around these.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

char *
format_float(double f, char *buf)
{ char *end, *o=buf;
  int decpt, sign;
  char *s = dtoa(f, 0, 30, &decpt, &sign, &end);

  DEBUG(2, Sdprintf("decpt=%d, sign=%d, len = %d, '%s'\n",
		    decpt, sign, end-s, s));

  if ( sign )
    *o++ = '-';

  if ( decpt <= 0 )			/* decimal dot before */
  { if ( decpt <= -4 )
    { *o++ = s[0];
      *o++ = '.';
      if ( end-s > 1 )
      { memcpy(o, s+1, end-s-1);
	o += end-s-1;
      } else
	*o++ = '0';
      sprintf(o, "e%d", decpt-1);
    } else
    { int i;

      *o++ = '0';
      *o++ = '.';
      for(i=0; i < -decpt; i++)
	*o++ = '0';
      memcpy(o, s, end-s);
      o[end-s] = 0;
    }
  } else if ( end-s > decpt )		/* decimal dot inside */
  { memcpy(o, s, decpt);
    o += decpt;
    *o++ = '.';
    memcpy(o, s+decpt, end-s-decpt);
    o[end-s-decpt] = 0;
  } else				/* decimal dot after */
  { int i;
    int trailing = decpt-(int)(end-s);

    if ( decpt > 15 )			/* over precision: use eE */
    { *o++ = s[0];
      *o++ = '.';
      if ( end-s > 1 )
      { trailing += (int)(end-s)-1;
	memcpy(o, s+1, end-s-1);
	o += end-s-1;
      } else
	*o++ = '0';
      sprintf(o, "e+%d", trailing);
    } else				/* within precision trail with .0 */
    { memcpy(o, s, end-s);
      o += end-s;

      for(i=(int)(end-s); i<decpt; i++)
	*o++ = '0';
      *o++ = '.';
      *o++ = '0';
      *o = 0;
    }
  }

  freedtoa(s);

  return buf;
}


static bool
WriteNumber(Number n, write_options *options)
{ GET_LD

  switch(n->type)
  { case V_INTEGER:
    { char buf[32];

      sprintf(buf, INT64_FORMAT, n->value.i);
      return PutToken(buf, options->out);
    }
#ifdef O_GMP
    case V_MPZ:
    { char tmp[1024];
      char *buf;
      size_t sz = mpz_sizeinbase(n->value.mpz, 10) + 2;
      bool rc;

      if ( sz <= sizeof(tmp) )
	buf = tmp;
      else
	buf = PL_malloc(sz);

      /* mpz_get_str() can perform large intermediate allocations :-( */
      EXCEPTION_GUARDED({ LD->gmp.persistent++;
			  mpz_get_str(buf, 10, n->value.mpz);
			  LD->gmp.persistent--;
			},
			{ LD->gmp.persistent--;
			  rc = PL_rethrow();
			})
      rc = PutToken(buf, options->out);
      if ( buf != tmp )
	PL_free(buf);

      return rc;
    }
    case V_MPQ:				/* should not get here */
#endif
    case V_FLOAT:
      assert(0);
  }

  fail;
}



static bool
writePrimitive(term_t t, write_options *options)
{ GET_LD
  double f;
  atom_t a;
  char buf[32];
  IOSTREAM *out = options->out;

#if O_ATTVAR
  if ( PL_is_attvar(t) )
    return writeAttVar(t, options);
#endif

  if ( PL_is_variable(t) )
    return PutToken(varName(t, buf), out);

  if ( PL_get_atom(t, &a) )
    return writeAtom(a, options);

  if ( PL_is_integer(t) )		/* beware of automatic conversion */
  { number n;

    PL_get_number(t, &n);

    return WriteNumber(&n, options);
  }

  if ( PL_get_float(t, &f) )
  { char *s = NULL;

#ifdef HAVE_FPCLASSIFY
    switch(fpclassify(f))
    { case FP_NAN:
	s = (true(options, PL_WRT_QUOTED) ? "'$NaN'" : "NaN");
        break;
      case FP_INFINITE:
	s = (true(options, PL_WRT_QUOTED) ? "'$Infinity'" : "Infinity");
        break;
    }
#else
#ifdef HAVE_FPCLASS
    switch(fpclass(f))
    { case FP_SNAN:
      case FP_QNAN:
	s = (true(options, PL_WRT_QUOTED) ? "'$NaN'" : "NaN");
        break;
      case FP_NINF:
      case FP_PINF:
	s = (true(options, PL_WRT_QUOTED) ? "'$Infinity'" : "Infinity");
        break;
      case FP_NDENORM:			/* pos/neg denormalized non-zero */
      case FP_PDENORM:
      case FP_NNORM:			/* pos/neg normalized non-zero */
      case FP_PNORM:
      case FP_NZERO:			/* pos/neg zero */
      case FP_PZERO:
	break;
    }
#else
#ifdef HAVE__FPCLASS
    switch(_fpclass(f))
    { case _FPCLASS_SNAN:
      case _FPCLASS_QNAN:
	s = (true(options, PL_WRT_QUOTED) ? "'$NaN'" : "NaN");
        break;
      case _FPCLASS_NINF:
      case _FPCLASS_PINF:
	s = (true(options, PL_WRT_QUOTED) ? "'$Infinity'" : "Infinity");
        break;
    }
#else
#ifdef HAVE_ISINF
    if ( isinf(f) )
    { s = (true(options, PL_WRT_QUOTED) ? "'$Infinity'" : "Infinity");
    } else
#endif
#ifdef HAVE_ISNAN
    if ( isnan(f) )
    { s = (true(options, PL_WRT_QUOTED) ? "'$NaN'" : "NaN");
    }
#endif
#endif /*HAVE__FPCLASS*/
#endif /*HAVE_FPCLASS*/
#endif /*HAVE_FPCLASSIFY*/

    if ( s )
    { return PutToken(s, out);
    } else
    { char buf[100];

      format_float(f, buf);

      return PutToken(buf, out);
    }
  }

#if O_STRING
  if ( PL_is_string(t) )
    return writeString(t, options);
#endif /* O_STRING */

  assert(0);
  fail;
}


word
pl_nl1(term_t stream)
{ IOSTREAM *s;

  if ( getOutputStream(stream, &s) )
  { Sputcode('\n', s);
    return streamStatus(s);
  }

  fail;
}

word
pl_nl(void)
{ return pl_nl1(0);
}

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Call user:portray/1 if defined.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

static int
callPortray(term_t arg, write_options *options)
{ predicate_t portray;

  if ( GD->cleaning > CLN_PROLOG )
    fail;				/* avoid dangerous callbacks */

  portray = _PL_predicate("portray", 1, "user", &GD->procedures.portray);

  if ( predicateHasClauses(portray) )
  { GET_LD
    wakeup_state wstate;
    IOSTREAM *old = Scurout;
    int rval;

    if ( !saveWakeup(&wstate, TRUE PASS_LD) )
      return FALSE;
    Scurout = options->out;
    rval = PL_call_predicate(NULL, PL_Q_NODEBUG|PL_Q_PASS_EXCEPTION,
			     portray, arg);
    if ( !rval && PL_exception(0) )
      rval = -1;
    Scurout = old;
    restoreWakeup(&wstate PASS_LD);

    return rval;
  }

  fail;
}


static bool
writeArgTerm(term_t t, int prec, write_options *options, bool arg)
{ int rval;
  int levelSave = options->depth;
  fid_t fid;

  if ( !(fid = PL_open_foreign_frame()) )
    return FALSE;

  if ( PL_handle_signals() < 0 )
  { rval = FALSE;
    goto out;
  }

  if ( ++options->depth > options->max_depth && options->max_depth )
    rval = PutString("...", options->out);
  else if ( PL_is_compound(t) )
  { visited v;

    v.address = address_of(t);
    if ( has_visited(options->visited, v.address) )
    { rval = PutString("**", options->out);
    } else
    { v.next = options->visited;
      options->visited = &v;
      rval = writeTerm2(t, prec, options, arg);
      options->visited = v.next;
    }
  } else
  { rval = writeTerm2(t, prec, options, arg);
  }

out:
  options->depth = levelSave;
  PL_close_foreign_frame(fid);

  return rval;
}

static bool
writeTerm(term_t t, int prec, write_options *options)
{
  return writeArgTerm(t, prec, options, FALSE);
}

static bool
writeList2(term_t list, write_options *options, int cyclic)
{ GET_LD
  term_t head = PL_new_term_ref();
  term_t l    = PL_copy_term_ref(list);

  TRY(Putc('[', options->out));
  for(;;)
  { PL_get_list(l, head, l);
    TRY(writeArgTerm(head, 999, options, TRUE));

    if ( PL_get_nil(l) )
      break;
    if ( ++options->depth >= options->max_depth && options->max_depth )
      return PutString("|...]", options->out);
    if ( !PL_is_functor(l, FUNCTOR_dot2) )
    { TRY(Putc('|', options->out));
      TRY(writeArgTerm(l, 999, options, TRUE));
      break;
    }

					/* cycle detection */
    { Word addr =  address_of(l);

      if ( has_visited(options->visited, addr) )
      { return PutString("|**]", options->out);
      } else if ( cyclic )
      { visited *v = alloca(sizeof(*v));
	v->address = addr;
	v->next = options->visited;
	options->visited = v;
      }
    }

    TRY(PutComma(options));
  }

  return Putc(']', options->out);
}


static bool
writeList(term_t list, write_options *options)
{ GET_LD
  visited *v = options->visited;
  Word tail;
  int rc;

  skip_list(valTermRef(list), &tail PASS_LD);
  rc = writeList2(list, options, isList(*tail));
  options->visited = v;

  return rc;
}



static bool
writeTerm2(term_t t, int prec, write_options *options, bool arg)
{ GET_LD
  atom_t functor;
  int arity, n;
  int op_type, op_pri;
  atom_t a;
  IOSTREAM *out = options->out;

  if ( !PL_is_variable(t) &&
       true(options, PL_WRT_PORTRAY) )
  { switch( callPortray(t, options) )
    { case TRUE:
	return TRUE;
      case FALSE:
	break;
      default:
	return FALSE;
    }
  }

  if ( PL_get_atom(t, &a) )
    { if ( !arg && prec < 1200 && priorityOperator((Module)NULL, a) > 0 )
    { if ( PutOpenBrace(out) &&
	   writeAtom(a, options) &&
	   PutCloseBrace(out) )
	succeed;
    } else
      return writeAtom(a, options);
  }

  if ( !PL_get_name_arity(t, &functor, &arity) )
  { return writePrimitive(t, options);
  } else
  { if ( arity == 1 &&
	 functor == ATOM_isovar &&			/* $VAR/1 */
	 true(options, PL_WRT_NUMBERVARS) )
    { int n;
      atom_t a;
      term_t arg = PL_new_term_ref();

      _PL_get_arg(1, t, arg);
#if __YAP_PROLOG__
      /* YAP supports $VAR(-1) as a quick hack to write singleton variables */
#define MIN_DOLLAR_VAR -1
#else
#define MIN_DOLLAR_VAR 0      
#endif
      if ( PL_get_integer(arg, &n) && n >= MIN_DOLLAR_VAR )
      { int i = n % 26;
	int j = n / 26;
	char buf[16];

#if __YAP_PROLOG__
	if ( n == -1 ) {
	  buf[0] = '_';
	  buf[1] = EOS;
	} else
#endif
	if ( j == 0 )
	{ buf[0] = i+'A';
	  buf[1] = EOS;
	} else
	{ sprintf(buf, "%c%d", i+'A', j);
	}

	return PutToken(buf, out);
      }
      if ( PL_get_atom(arg, &a) )
      { write_options o2 = *options;
	clear(&o2, PL_WRT_QUOTED);

	return writeAtom(a, &o2);
      }
    }


    if ( false(options, PL_WRT_IGNOREOPS) )
    { term_t arg = PL_new_term_ref();

      if ( arity == 1 )
      { if ( functor == ATOM_curl )	/* {a,b,c} */
	{ _PL_get_arg(1, t, arg);
	  TRY(Putc('{', out));
	  TRY(writeTerm(arg, 1200, options) &&
	      Putc('}', out));

	  succeed;
	}

					  /* op <term> */
	if ( currentOperator(options->module, functor, OP_PREFIX,
			     &op_type, &op_pri) )
	{ term_t arg = PL_new_term_ref();
	  int embrace;

	  embrace = ( op_pri > prec );

	  _PL_get_arg(1, t, arg);
	  if ( embrace )
	  { TRY(PutOpenBrace(out));
	  }
	  TRY(writeAtom(functor, options));

				/* +/-(Number) : avoid parsing as number */
	  if ( (functor == ATOM_minus || functor == ATOM_plus) &&
	       PL_is_number(arg) )
	  { TRY(Putc('(', out));
	    TRY(writeTerm(arg, 999, options));
	    TRY(Putc(')', out));
	  } else
	  { TRY(writeTerm(arg,
			  op_type == OP_FX ? op_pri-1 : op_pri,
			  options));
	  }
	  if ( embrace )
	  { TRY(PutCloseBrace(out));
	  }

	  succeed;
	}

					  /* <term> op */
	if ( currentOperator(options->module, functor, OP_POSTFIX,
			     &op_type, &op_pri) )
	{ term_t arg = PL_new_term_ref();

	  _PL_get_arg(1, t, arg);
	  if ( op_pri > prec )
	    TRY(PutOpenBrace(out));
	  TRY(writeTerm(arg,
			op_type == OP_XF ? op_pri-1 : op_pri,
			options));
	  TRY(writeAtom(functor, options));
	  if (op_pri > prec)
	    TRY(PutCloseBrace(out));

	  succeed;
	}
      } else if ( arity == 2 )
      { if ( functor == ATOM_dot )	/* [...] */
	  return writeList(t, options);

					  /* <term> op <term> */
	if ( currentOperator(options->module, functor, OP_INFIX,
			     &op_type, &op_pri) )
	{ term_t l = PL_new_term_ref();
	  term_t r = PL_new_term_ref();

	  _PL_get_arg(1, t, l);
	  _PL_get_arg(2, t, r);

	  if ( op_pri > prec )
	    TRY(PutOpenBrace(out));
	  TRY(writeTerm(l,
			op_type == OP_XFX || op_type == OP_XFY
				? op_pri-1 : op_pri,
			options));
	  if ( functor == ATOM_comma )
	  { TRY(PutComma(options));
	  } else
	  { switch(writeAtom(functor, options))
	    { case FALSE:
		fail;
	      case TRUE_WITH_SPACE:
		TRY(Putc(' ', out));
	    }
	  }
	  TRY(writeTerm(r,
			op_type == OP_XFX || op_type == OP_YFX
				? op_pri-1 : op_pri,
			options));
	  if ( op_pri > prec )
	    TRY(PutCloseBrace(out));
	  succeed;
	}
      }
    }
					/* functor(<args> ...) */
    { term_t a = PL_new_term_ref();

      TRY(writeAtom(functor, options) &&
	  Putc('(', out));
      for(n=0; n<arity; n++)
      { if (n > 0)
	  TRY(PutComma(options));
	_PL_get_arg(n+1, t, a);
	TRY(writeArgTerm(a, 999, options, TRUE));
      }
      return Putc(')', out);
    }
  }
}


int
writeAttributeMask(atom_t a)
{ if ( a == ATOM_ignore )
  { return PL_WRT_ATTVAR_IGNORE;
  } else if ( a == ATOM_dots )
  { return PL_WRT_ATTVAR_DOTS;
  } else if ( a == ATOM_write )
  { return PL_WRT_ATTVAR_WRITE;
  } else if ( a == ATOM_portray )
  { return PL_WRT_ATTVAR_PORTRAY;
  } else
    return 0;
}


static int
writeBlobMask(atom_t a)
{ if ( a == ATOM_default )
  { return 0;
  } else if ( a == ATOM_portray )
  { return PL_WRT_BLOB_PORTRAY;
  } else
    return -1;
}


static const opt_spec write_term_options[] =
{ { ATOM_quoted,	    OPT_BOOL },
  { ATOM_ignore_ops,	    OPT_BOOL },
  { ATOM_numbervars,        OPT_BOOL },
  { ATOM_portray,           OPT_BOOL },
  { ATOM_character_escapes, OPT_BOOL },
  { ATOM_max_depth,	    OPT_INT  },
  { ATOM_module,	    OPT_ATOM },
  { ATOM_backquoted_string, OPT_BOOL },
  { ATOM_attributes,	    OPT_ATOM },
  { ATOM_priority,	    OPT_INT },
  { ATOM_partial,	    OPT_BOOL },
  { ATOM_spacing,	    OPT_ATOM },
  { ATOM_blobs,		    OPT_ATOM },
  { NULL_ATOM,	     	    0 }
};

word
pl_write_term3(term_t stream, term_t term, term_t opts)
{ GET_LD
  bool quoted     = FALSE;
  bool ignore_ops = FALSE;
  bool numbervars = -1;			/* not set */
  bool portray    = FALSE;
  bool bqstring   = truePrologFlag(PLFLAG_BACKQUOTED_STRING);
  bool charescape = -1;			/* not set */
  atom_t mname    = ATOM_user;
  atom_t attr     = ATOM_nil;
  atom_t blobs    = ATOM_nil;
  int  priority   = 1200;
  bool partial    = FALSE;
  IOSTREAM *s;
  write_options options;
  int rc;

  memset(&options, 0, sizeof(options));
  options.spacing = ATOM_standard;

  if ( !scan_options(opts, 0, ATOM_write_option, write_term_options,
		     &quoted, &ignore_ops, &numbervars, &portray,
		     &charescape, &options.max_depth, &mname,
		     &bqstring, &attr, &priority, &partial, &options.spacing,
		     &blobs) )
    fail;

  if ( attr == ATOM_nil )
  { options.flags |= LD->prolog_flag.write_attributes;
  } else
  { int mask = writeAttributeMask(attr);

    if ( !mask )
      return PL_error(NULL, 0, NULL, ERR_DOMAIN, ATOM_write_option, opts);

    options.flags |= mask;
  }
  if ( blobs != ATOM_nil )
  { int mask = writeBlobMask(blobs);

    if ( mask < 0 )
      return PL_error(NULL, 0, NULL, ERR_DOMAIN, ATOM_write_option, opts);

    options.flags |= mask;
  }
  if ( priority < 0 || priority > OP_MAXPRIORITY )
  { term_t t = PL_new_term_ref();
    PL_put_integer(t, priority);

    return PL_error(NULL, 0, NULL, ERR_DOMAIN, ATOM_operator_priority, t);
  }
  switch( options.spacing )
  { case ATOM_standard:
    case ATOM_next_argument:
      break;
    default:
    { term_t t = PL_new_term_ref();
      PL_put_atom(t, options.spacing);

      return PL_error(NULL, 0, NULL, ERR_DOMAIN, ATOM_spacing, t);
    }
  }

  if ( !getOutputStream(stream, &s) )
    fail;

  options.module = lookupModule(mname);
  if ( charescape == TRUE ||
       //       (charescape == -1 && true(options.module, CHARESCAPE)) )
       charEscapeWriteOption(options))
    options.flags |= PL_WRT_CHARESCAPES;
  if ( numbervars == -1 )
    numbervars = (portray ? TRUE : FALSE);

  if ( quoted )     options.flags |= PL_WRT_QUOTED;
  if ( ignore_ops ) options.flags |= PL_WRT_IGNOREOPS;
  if ( numbervars ) options.flags |= PL_WRT_NUMBERVARS;
  if ( portray )    options.flags |= PL_WRT_PORTRAY;
  if ( bqstring )   options.flags |= PL_WRT_BACKQUOTED_STRING;

  options.out = s;
  if ( !partial )
    PutOpenToken(EOF, s);		/* reset this */
  if ( (options.flags & PL_WRT_QUOTED) && !(s->flags&SIO_REPPL) )
  { s->flags |= SIO_REPPL;
    rc = writeTerm(term, priority, &options);
    s->flags &= ~SIO_REPPL;
  } else
  { rc = writeTerm(term, priority, &options);
  }

  return streamStatus(s) && rc;
}


word
pl_write_term(term_t term, term_t options)
{ return pl_write_term3(0, term, options);
}


int
PL_write_term(IOSTREAM *s, term_t term, int precedence, int flags)
{ write_options options;

  memset(&options, 0, sizeof(options));
  options.flags	    = flags;
  options.out	    = s;
  options.module    = MODULE_user;

  PutOpenToken(EOF, s);			/* reset this */
  return writeTerm(term, precedence, &options);
}


static word
do_write2(term_t stream, term_t term, int flags)
{ GET_LD
  IOSTREAM *s;

  if ( getOutputStream(stream, &s) )
  { write_options options;
    int rc;

    memset(&options, 0, sizeof(options));
    options.flags     = flags;
    options.out	      = s;
    options.module    = MODULE_user;
    //    if ( options.module && true(options.module, CHARESCAPE) )
    if (charEscapeWriteOption(options))
      options.flags |= PL_WRT_CHARESCAPES;
    if ( truePrologFlag(PLFLAG_BACKQUOTED_STRING) )
      options.flags |= PL_WRT_BACKQUOTED_STRING;

    PutOpenToken(EOF, s);		/* reset this */
    rc = writeTerm(term, 1200, &options);

    return streamStatus(s) && rc;
  }

  return FALSE;
}


word
pl_write2(term_t stream, term_t term)
{ return do_write2(stream, term, PL_WRT_NUMBERVARS);
}

word
pl_writeq2(term_t stream, term_t term)
{ return do_write2(stream, term, PL_WRT_QUOTED|PL_WRT_NUMBERVARS);
}

word
pl_print2(term_t stream, term_t term)
{ return do_write2(stream, term,
		   PL_WRT_PORTRAY|PL_WRT_NUMBERVARS);
}

word
pl_write_canonical2(term_t stream, term_t term)
{ GET_LD
  fid_t fid;
  nv_options options;
  word rc;

  if ( !(fid = PL_open_foreign_frame()) )
    return FALSE;
  options.functor = FUNCTOR_isovar1;
  options.on_attvar = AV_SKIP;
  options.singletons = TRUE;
  numberVars(term, &options, 0 PASS_LD);
  rc = do_write2(stream, term,
		 PL_WRT_QUOTED|PL_WRT_IGNOREOPS|PL_WRT_NUMBERVARS);
  PL_discard_foreign_frame(fid);

  return rc;
}

word
pl_write(term_t term)
{ return pl_write2(0, term);
}

word
pl_writeq(term_t term)
{ return pl_writeq2(0, term);
}

word
pl_print(term_t term)
{ return pl_print2(0, term);
}

word
pl_write_canonical(term_t term)
{ return pl_write_canonical2(0, term);
}

word					/* for debugging purposes! */
pl_writeln(term_t term)
{ if ( PL_write_term(Serror, term, 1200,
		     PL_WRT_QUOTED|PL_WRT_NUMBERVARS) &&
       Sdprintf("\n") >= 0 )
    succeed;

  fail;
}


static
PRED_IMPL("$put_token", 2, put_token, 0)
{ char *s;
  size_t len;
  IOSTREAM *out;

  if ( !PL_get_stream_handle(A1, &out) )
    fail;
  if ( !PL_get_nchars(A2, &len, &s, CVT_ATOM|CVT_STRING|CVT_EXCEPTION) )
    fail;

  if ( PutTokenN(s, len, out) )
    return PL_release_stream(out);

  PL_release_stream(out);
  fail;
}


		 /*******************************
		 *      PUBLISH PREDICATES	*
		 *******************************/

BeginPredDefs(write)
  PRED_DEF("$put_token", 2, put_token, 0)
EndPredDefs