eqv? not a generic, equal? dispatches to generic only for objects

[bpt/guile.git] / libguile / eq.c

/* Copyright (C) 1995,1996,1997,1998,2000,2001,2003, 2004, 2006, 2009 Free Software Foundation, Inc.
 * 
 * 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 3 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., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */

\f
#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#include "libguile/_scm.h"
#include "libguile/array-map.h"
#include "libguile/stackchk.h"
#include "libguile/strorder.h"
#include "libguile/async.h"
#include "libguile/root.h"
#include "libguile/smob.h"
#include "libguile/arrays.h"
#include "libguile/vectors.h"
#include "libguile/bytevectors.h"

#include "libguile/struct.h"
#include "libguile/goops.h"

#include "libguile/validate.h"
#include "libguile/eq.h"

#include "libguile/private-options.h"

\f

#ifdef HAVE_STRING_H
#include <string.h>
#endif
\f

SCM_DEFINE1 (scm_eq_p, "eq?", scm_tc7_rpsubr,
             (SCM x, SCM y),
	    "Return @code{#t} if @var{x} and @var{y} are the same object,\n"
	    "except for numbers and characters.  For example,\n"
	    "\n"
	    "@example\n"
	    "(define x (vector 1 2 3))\n"
	    "(define y (vector 1 2 3))\n"
	    "\n"
	    "(eq? x x)  @result{} #t\n"
	    "(eq? x y)  @result{} #f\n"
	    "@end example\n"
	    "\n"
	    "Numbers and characters are not equal to any other object, but\n"
	    "the problem is they're not necessarily @code{eq?} to themselves\n"
	    "either.  This is even so when the number comes directly from a\n"
	    "variable,\n"
	    "\n"
	    "@example\n"
	    "(let ((n (+ 2 3)))\n"
	    "  (eq? n n))       @result{} *unspecified*\n"
	    "@end example\n"
	    "\n"
	    "Generally @code{eqv?} should be used when comparing numbers or\n"
	    "characters.  @code{=} or @code{char=?} can be used too.\n"
	    "\n"
	    "It's worth noting that end-of-list @code{()}, @code{#t},\n"
	    "@code{#f}, a symbol of a given name, and a keyword of a given\n"
	    "name, are unique objects.  There's just one of each, so for\n"
	    "instance no matter how @code{()} arises in a program, it's the\n"
	    "same object and can be compared with @code{eq?},\n"
	    "\n"
	    "@example\n"
	    "(define x (cdr '(123)))\n"
	    "(define y (cdr '(456)))\n"
	    "(eq? x y) @result{} #t\n"
	    "\n"
	    "(define x (string->symbol \"foo\"))\n"
	    "(eq? x 'foo) @result{} #t\n"
	    "@end example")
#define FUNC_NAME s_scm_eq_p
{
  return scm_from_bool (scm_is_eq (x, y));
}
#undef FUNC_NAME

/* We compare doubles in a special way for 'eqv?' to be able to
   distinguish plus and minus zero and to identify NaNs.
*/

static int
real_eqv (double x, double y)
{
  return !memcmp (&x, &y, sizeof(double)) || (x != x && y != y);
}

#include <stdio.h>
SCM_DEFINE1 (scm_eqv_p, "eqv?", scm_tc7_rpsubr,
             (SCM x, SCM y),
	    "Return @code{#t} if @var{x} and @var{y} are the same object, or\n"
	    "for characters and numbers the same value.\n"
	    "\n"
	    "On objects except characters and numbers, @code{eqv?} is the\n"
	    "same as @code{eq?}, it's true if @var{x} and @var{y} are the\n"
	    "same object.\n"
	    "\n"
	    "If @var{x} and @var{y} are numbers or characters, @code{eqv?}\n"
	    "compares their type and value.  An exact number is not\n"
	    "@code{eqv?} to an inexact number (even if their value is the\n"
	    "same).\n"
	    "\n"
	    "@example\n"
	    "(eqv? 3 (+ 1 2)) @result{} #t\n"
	    "(eqv? 1 1.0)     @result{} #f\n"
	    "@end example")
#define FUNC_NAME s_scm_eqv_p
{
  if (scm_is_eq (x, y))
    return SCM_BOOL_T;
  if (SCM_IMP (x))
    return SCM_BOOL_F;
  if (SCM_IMP (y))
    return SCM_BOOL_F;
  /* this ensures that types and scm_length are the same. */

  if (SCM_CELL_TYPE (x) != SCM_CELL_TYPE (y))
    {
      /* fractions use 0x10000 as a flag (at the suggestion of Marius Vollmer),
	 but this checks the entire type word, so fractions may be accidentally
	 flagged here as unequal.  Perhaps I should use the 4th double_cell word?
      */

      /* treat mixes of real and complex types specially */
      if (SCM_INEXACTP (x))
	{
	  if (SCM_REALP (x))
	    return scm_from_bool (SCM_COMPLEXP (y)
			     && real_eqv (SCM_REAL_VALUE (x),
					  SCM_COMPLEX_REAL (y))
			     && SCM_COMPLEX_IMAG (y) == 0.0);
	  else
	    return scm_from_bool (SCM_REALP (y)
			     && real_eqv (SCM_COMPLEX_REAL (x),
					  SCM_REAL_VALUE (y))
			     && SCM_COMPLEX_IMAG (x) == 0.0);
	}

      if (SCM_FRACTIONP (x) && SCM_FRACTIONP (y))
	return scm_i_fraction_equalp (x, y);
      return SCM_BOOL_F;
    }
  if (SCM_NUMP (x))
    {
      if (SCM_BIGP (x)) {
	return scm_from_bool (scm_i_bigcmp (x, y) == 0);
      } else if (SCM_REALP (x)) {
	return scm_from_bool (real_eqv (SCM_REAL_VALUE (x), SCM_REAL_VALUE (y)));
      } else if (SCM_FRACTIONP (x)) {
	return scm_i_fraction_equalp (x, y);
      } else { /* complex */
	return scm_from_bool (real_eqv (SCM_COMPLEX_REAL (x),
				   SCM_COMPLEX_REAL (y)) 
			 && real_eqv (SCM_COMPLEX_IMAG (x),
				      SCM_COMPLEX_IMAG (y)));
      }
    }
  return SCM_BOOL_F;
}
#undef FUNC_NAME


SCM_PRIMITIVE_GENERIC_1 (scm_equal_p, "equal?", scm_tc7_rpsubr,
			 (SCM x, SCM y),
	    "Return @code{#t} if @var{x} and @var{y} are the same type, and\n"
	    "their contents or value are equal.\n"
	    "\n"
	    "For a pair, string, vector or array, @code{equal?} compares the\n"
	    "contents, and does so using using the same @code{equal?}\n"
	    "recursively, so a deep structure can be traversed.\n"
	    "\n"
	    "@example\n"
	    "(equal? (list 1 2 3) (list 1 2 3))   @result{} #t\n"
	    "(equal? (list 1 2 3) (vector 1 2 3)) @result{} #f\n"
	    "@end example\n"
	    "\n"
	    "For other objects, @code{equal?} compares as per @code{eqv?},\n"
	    "which means characters and numbers are compared by type and\n"
	    "value (and like @code{eqv?}, exact and inexact numbers are not\n"
	    "@code{equal?}, even if their value is the same).\n"
	    "\n"
	    "@example\n"
	    "(equal? 3 (+ 1 2)) @result{} #t\n"
	    "(equal? 1 1.0)     @result{} #f\n"
	    "@end example\n"
	    "\n"
	    "Hash tables are currently only compared as per @code{eq?}, so\n"
	    "two different tables are not @code{equal?}, even if their\n"
	    "contents are the same.\n"
	    "\n"
	    "@code{equal?} does not support circular data structures, it may\n"
	    "go into an infinite loop if asked to compare two circular lists\n"
	    "or similar.\n"
	    "\n"
	    "New application-defined object types (Smobs) have an\n"
	    "@code{equalp} handler which is called by @code{equal?}.  This\n"
	    "lets an application traverse the contents or control what is\n"
	    "considered @code{equal?} for two such objects.  If there's no\n"
	    "handler, the default is to just compare as per @code{eq?}.")
#define FUNC_NAME s_scm_equal_p
{
  SCM_CHECK_STACK;
 tailrecurse:
  SCM_TICK;
  if (scm_is_eq (x, y))
    return SCM_BOOL_T;
  if (SCM_IMP (x))
    return SCM_BOOL_F;
  if (SCM_IMP (y))
    return SCM_BOOL_F;
  if (scm_is_pair (x) && scm_is_pair (y))
    {
      if (scm_is_false (scm_equal_p (SCM_CAR (x), SCM_CAR (y))))
	return SCM_BOOL_F;
      x = SCM_CDR(x);
      y = SCM_CDR(y);
      goto tailrecurse;
    }
  if (SCM_TYP7 (x) == scm_tc7_string && SCM_TYP7 (y) == scm_tc7_string)
    return scm_string_equal_p (x, y);
  if (SCM_TYP7 (x) == scm_tc7_bytevector && SCM_TYP7 (y) == scm_tc7_bytevector)
    return scm_bytevector_eq_p (x, y);
  if (SCM_TYP7 (x) == scm_tc7_smob && SCM_TYP16 (x) == SCM_TYP16 (y))
    {
      int i = SCM_SMOBNUM (x);
      if (!(i < scm_numsmob))
	return SCM_BOOL_F;
      if (scm_smobs[i].equalp)
	return (scm_smobs[i].equalp) (x, y);
      else
	goto generic_equal;
    }
  /* This ensures that types and scm_length are the same.  */
  if (SCM_CELL_TYPE (x) != SCM_CELL_TYPE (y))
    {
      /* treat mixes of real and complex types specially */
      if (SCM_INEXACTP (x) && SCM_INEXACTP (y))
	{
	  if (SCM_REALP (x))
	    return scm_from_bool (SCM_COMPLEXP (y)
			     && SCM_REAL_VALUE (x) == SCM_COMPLEX_REAL (y)
			     && SCM_COMPLEX_IMAG (y) == 0.0);
	  else
	    return scm_from_bool (SCM_REALP (y)
			     && SCM_COMPLEX_REAL (x) == SCM_REAL_VALUE (y)
			     && SCM_COMPLEX_IMAG (x) == 0.0);
	}

      /* Vectors can be equal to one-dimensional arrays.
       */
      if (SCM_I_ARRAYP (x) || SCM_I_ARRAYP (y))
	return scm_array_equal_p (x, y);

      return SCM_BOOL_F;
    }
  switch (SCM_TYP7 (x))
    {
    default:
      break;
    case scm_tc7_number:
      switch SCM_TYP16 (x)
        {
        case scm_tc16_big:
          return scm_bigequal (x, y);
        case scm_tc16_real:
          return scm_real_equalp (x, y);
        case scm_tc16_complex:
          return scm_complex_equalp (x, y);
	case scm_tc16_fraction:
          return scm_i_fraction_equalp (x, y);
        }
    case scm_tc7_vector:
    case scm_tc7_wvect:
      return scm_i_vector_equal_p (x, y);
    }
  /* Check equality between structs of equal type (see cell-type test above). */
  if (SCM_STRUCTP (x))
    {
      if (SCM_INSTANCEP (x))
        goto generic_equal;
      else
        return scm_i_struct_equalp (x, y);
    }

  /* Otherwise just return false. Dispatching to the generic is the wrong thing
     here, as we can hit this case for any two objects of the same type that we
     think are distinct, like different symbols. */
  return SCM_BOOL_F;
  
 generic_equal:
  if (SCM_UNPACK (g_scm_equal_p))
    return scm_call_generic_2 (g_scm_equal_p, x, y);
  else
    return SCM_BOOL_F;
}
#undef FUNC_NAME


\f



void
scm_init_eq ()
{
#include "libguile/eq.x"
}


/*
  Local Variables:
  c-file-style: "gnu"
  End:
*/