The R Project SVN R

/*
 *  R : A Computer Language for Statistical Data Analysis
 *  Copyright (C) 1995, 1996  Robert Gentleman and Ross Ihaka
 *  Copyright (C) 1997--2008  Robert Gentleman, Ross Ihaka and the
 *                            R Development Core Team
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, a copy is available at
 *  http://www.r-project.org/Licenses/
 */

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

#include <Defn.h>
#include <Rmath.h>

static SEXP installAttrib(SEXP, SEXP, SEXP);
static SEXP removeAttrib(SEXP, SEXP);

SEXP comment(SEXP);
static SEXP commentgets(SEXP, SEXP);

static SEXP row_names_gets(SEXP vec , SEXP val)
{
    SEXP ans;

    if (vec == R_NilValue)
    error(_("attempt to set an attribute on NULL"));

    if(isReal(val) && length(val) == 2 && ISNAN(REAL(val)[0]) ) {
    /* This should not happen, but if a careless user dput()s a
       data frame and sources the result, it will */
    PROTECT(val = coerceVector(val, INTSXP));
    ans =  installAttrib(vec, R_RowNamesSymbol, val);
    UNPROTECT(1);
    return ans;
    }
    if(isInteger(val)) {
    Rboolean OK_compact = TRUE;
    int i, n = LENGTH(val);
    if(n == 2 && INTEGER(val)[0] == NA_INTEGER) {
        n = INTEGER(val)[1];
    } else if (n > 2) {
        for(i = 0; i < n; i++)
        if(INTEGER(val)[i] != i+1) {
            OK_compact = FALSE;
            break;
        }
    } else OK_compact = FALSE;
    if(OK_compact) {
        /* we hide the length in an impossible integer vector */
        PROTECT(val = allocVector(INTSXP, 2));
        INTEGER(val)[0] = NA_INTEGER;
        INTEGER(val)[1] = n;
        ans =  installAttrib(vec, R_RowNamesSymbol, val);
        UNPROTECT(1);
        return ans;
    }
    } else if(!isString(val))
    error(_("row names must be 'character' or 'integer', not '%s'"),
          type2char(TYPEOF(val)));
    PROTECT(val);
    ans =  installAttrib(vec, R_RowNamesSymbol, val);
    UNPROTECT(1);
    return ans;
}

/* used in removeAttrib, commentgets and classgets */
static SEXP stripAttrib(SEXP tag, SEXP lst)
{
    if(lst == R_NilValue) return lst;
    if(tag == TAG(lst)) return stripAttrib(tag, CDR(lst));
    SETCDR(lst, stripAttrib(tag, CDR(lst)));
    return lst;
}

/* NOTE: For environments serialize.c calls this function to find if
   there is a class attribute in order to reconstruct the object bit
   if needed.  This means the function cannot use OBJECT(vec) == 0 to
   conclude that the class attribute is R_NilValue.  If you want to
   rewrite this function to use such a pre-test, be sure to adjust
   serialize.c accordingly.  LT */
SEXP attribute_hidden getAttrib0(SEXP vec, SEXP name)
{
    SEXP s;
    int len, i, any;

    if (name == R_NamesSymbol) {
    if(isVector(vec) || isList(vec) || isLanguage(vec)) {
        s = getAttrib(vec, R_DimSymbol);
        if(TYPEOF(s) == INTSXP && length(s) == 1) {
        s = getAttrib(vec, R_DimNamesSymbol);
        if(!isNull(s)) {
            SET_NAMED(VECTOR_ELT(s, 0), 2);
            return VECTOR_ELT(s, 0);
        }
        }
    }
    if (isList(vec) || isLanguage(vec)) {
        len = length(vec);
        PROTECT(s = allocVector(STRSXP, len));
        i = 0;
        any = 0;
        for ( ; vec != R_NilValue; vec = CDR(vec), i++) {
        if (TAG(vec) == R_NilValue)
            SET_STRING_ELT(s, i, R_BlankString);
        else if (isSymbol(TAG(vec))) {
            any = 1;
            SET_STRING_ELT(s, i, PRINTNAME(TAG(vec)));
        }
        else
            error(_("getAttrib: invalid type (%s) for TAG"),
              type2char(TYPEOF(TAG(vec))));
        }
        UNPROTECT(1);
        if (any) {
        if (!isNull(s)) SET_NAMED(s, 2);
        return (s);
        }
        return R_NilValue;
    }
    }
    /* This is where the old/new list adjustment happens. */
    for (s = ATTRIB(vec); s != R_NilValue; s = CDR(s))
    if (TAG(s) == name) {
        if (name == R_DimNamesSymbol && TYPEOF(CAR(s)) == LISTSXP) {
        SEXP _new, old;
        int i;
        _new = allocVector(VECSXP, length(CAR(s)));
        old = CAR(s);
        i = 0;
        while (old != R_NilValue) {
            SET_VECTOR_ELT(_new, i++, CAR(old));
            old = CDR(old);
        }
        SET_NAMED(_new, 2);
        return _new;
        }
        SET_NAMED(CAR(s), 2);
        return CAR(s);
    }
    return R_NilValue;
}

SEXP getAttrib(SEXP vec, SEXP name)
{
    /* pre-test to avoid expensive operations if clearly not needed -- LT */
    if (ATTRIB(vec) == R_NilValue &&
    ! (TYPEOF(vec) == LISTSXP || TYPEOF(vec) == LANGSXP))
    return R_NilValue;

    if (isString(name)) name = install(translateChar(STRING_ELT(name, 0)));

    /* special test for c(NA, n) rownames of data frames: */
    if (name == R_RowNamesSymbol) {
    SEXP s = getAttrib0(vec, R_RowNamesSymbol);
    if(isInteger(s) && LENGTH(s) == 2 && INTEGER(s)[0] == NA_INTEGER) {
        int i, n = abs(INTEGER(s)[1]);
        PROTECT(s = allocVector(INTSXP, n));
        for(i = 0; i < n; i++)
        INTEGER(s)[i] = i+1;
        UNPROTECT(1);
    }
    return s;
    } else
    return getAttrib0(vec, name);
}

SEXP R_shortRowNames(SEXP vec, SEXP stype)
{
    /* return  n if the data frame 'vec' has c(NA, n) rownames;
     *         nrow(.) otherwise;  note that data frames with nrow(.) == 0
     *      have no row.names.
     ==> is also used in dim.data.frame() */
    SEXP s = getAttrib0(vec, R_RowNamesSymbol), ans = s;
    int type = asInteger(stype);

    if( type < 0 || type > 2)
    error(_("invalid '%s' argument"), "type");

    if(type >= 1) {
    int n = (isInteger(s) && LENGTH(s) == 2 && INTEGER(s)[0] == NA_INTEGER)
        ? INTEGER(s)[1] : (isNull(s) ? 0 : LENGTH(s));
    ans = ScalarInteger((type == 1) ? n : abs(n));
    }
    return ans;
}

/* This is allowed to change 'out' */
SEXP R_copyDFattr(SEXP in, SEXP out)
{
    SET_ATTRIB(out, ATTRIB(in));
    IS_S4_OBJECT(in) ?  SET_S4_OBJECT(out) : UNSET_S4_OBJECT(out);
    SET_OBJECT(out, OBJECT(in));
    return out;
}

/* 'name' should be 1-element STRSXP or SYMSXP */
SEXP setAttrib(SEXP vec, SEXP name, SEXP val)
{
    if (isString(name))
    name = install(translateChar(STRING_ELT(name, 0)));
    if (val == R_NilValue)
    return removeAttrib(vec, name);

    /* We allow attempting to remove names from NULL */
    if (vec == R_NilValue)
    error(_("attempt to set an attribute on NULL"));

    PROTECT(vec);
    PROTECT(name);
    if (NAMED(val)) val = duplicate(val);
    SET_NAMED(val, NAMED(val) | NAMED(vec));
    UNPROTECT(2);

    if (name == R_NamesSymbol)
    return namesgets(vec, val);
    else if (name == R_DimSymbol)
    return dimgets(vec, val);
    else if (name == R_DimNamesSymbol)
    return dimnamesgets(vec, val);
    else if (name == R_ClassSymbol)
    return classgets(vec, val);
    else if (name == R_TspSymbol)
    return tspgets(vec, val);
    else if (name == R_CommentSymbol)
    return commentgets(vec, val);
    else if (name == R_RowNamesSymbol)
    return row_names_gets(vec, val);
    else
    return installAttrib(vec, name, val);
}

/* This is called in the case of binary operations to copy */
/* most attributes from (one of) the input arguments to */
/* the output.  Note that the Dim and Names attributes */
/* should have been assigned elsewhere. */

void copyMostAttrib(SEXP inp, SEXP ans)
{
    SEXP s;

    if (ans == R_NilValue)
    error(_("attempt to set an attribute on NULL"));

    PROTECT(ans);
    PROTECT(inp);
    for (s = ATTRIB(inp); s != R_NilValue; s = CDR(s)) {
    if ((TAG(s) != R_NamesSymbol) &&
        (TAG(s) != R_DimSymbol) &&
        (TAG(s) != R_DimNamesSymbol)) {
        installAttrib(ans, TAG(s), CAR(s));
    }
    }
    SET_OBJECT(ans, OBJECT(inp));
    IS_S4_OBJECT(inp) ?  SET_S4_OBJECT(ans) : UNSET_S4_OBJECT(ans);
    UNPROTECT(2);
}

/* version that does not preserve ts information, for subsetting */
void attribute_hidden copyMostAttribNoTs(SEXP inp, SEXP ans)
{
    SEXP s;

    if (ans == R_NilValue)
    error(_("attempt to set an attribute on NULL"));

    PROTECT(ans);
    PROTECT(inp);
    for (s = ATTRIB(inp); s != R_NilValue; s = CDR(s)) {
    if ((TAG(s) != R_NamesSymbol) &&
        (TAG(s) != R_ClassSymbol) &&
        (TAG(s) != R_TspSymbol) &&
        (TAG(s) != R_DimSymbol) &&
        (TAG(s) != R_DimNamesSymbol)) {
        installAttrib(ans, TAG(s), CAR(s));
    } else if (TAG(s) == R_ClassSymbol) {
        SEXP cl = CAR(s);
        int i;
        Rboolean ists = FALSE;
        for (i = 0; i < LENGTH(cl); i++)
        if (strcmp(CHAR(STRING_ELT(cl, i)), "ts") == 0) { /* ASCII */
            ists = TRUE;
            break;
        }
        if (!ists) installAttrib(ans, TAG(s), cl);
        else if(LENGTH(cl) <= 1) {
        } else {
        SEXP new_cl;
        int i, j, l = LENGTH(cl);
        PROTECT(new_cl = allocVector(STRSXP, l - 1));
        for (i = 0, j = 0; i < l; i++)
            if (strcmp(CHAR(STRING_ELT(cl, i)), "ts")) /* ASCII */
            SET_STRING_ELT(new_cl, j++, STRING_ELT(cl, i));
        installAttrib(ans, TAG(s), new_cl);
        UNPROTECT(1);
        }
    }
    }
    SET_OBJECT(ans, OBJECT(inp));
    IS_S4_OBJECT(inp) ?  SET_S4_OBJECT(ans) : UNSET_S4_OBJECT(ans);
    UNPROTECT(2);
}

static SEXP installAttrib(SEXP vec, SEXP name, SEXP val)
{
    SEXP s, t;

    PROTECT(vec);
    PROTECT(name);
    PROTECT(val);
    for (s = ATTRIB(vec); s != R_NilValue; s = CDR(s)) {
    if (TAG(s) == name) {
        SETCAR(s, val);
        UNPROTECT(3);
        return val;
    }
    }
    s = allocList(1);
    SETCAR(s, val);
    SET_TAG(s, name);
    if (ATTRIB(vec) == R_NilValue)
    SET_ATTRIB(vec, s);
    else {
    t = nthcdr(ATTRIB(vec), length(ATTRIB(vec)) - 1);
    SETCDR(t, s);
    }
    UNPROTECT(3);
    return val;
}

static SEXP removeAttrib(SEXP vec, SEXP name)
{
    SEXP t;
    if (name == R_NamesSymbol && isList(vec)) {
    for (t = vec; t != R_NilValue; t = CDR(t))
        SET_TAG(t, R_NilValue);
    return R_NilValue;
    }
    else {
    if (name == R_DimSymbol)
        SET_ATTRIB(vec, stripAttrib(R_DimNamesSymbol, ATTRIB(vec)));
    SET_ATTRIB(vec, stripAttrib(name, ATTRIB(vec)));
    if (name == R_ClassSymbol)
        SET_OBJECT(vec, 0);
    }
    return R_NilValue;
}

static void checkNames(SEXP x, SEXP s)
{
    if (isVector(x) || isList(x) || isLanguage(x)) {
    if (!isVector(s) && !isList(s))
        error(_("invalid type (%s) for 'names': must be vector"),
          type2char(TYPEOF(s)));
    if (length(x) != length(s))
        error(_("'names' attribute [%d] must be the same length as the vector [%d]"), length(s), length(x));
    }
    else if(IS_S4_OBJECT(x)) {
      /* leave validity checks to S4 code */
    }
    else error(_("names() applied to a non-vector"));
}


/* Time Series Parameters */

static void badtsp(void)
{
    error(_("invalid time series parameters specified"));
}

SEXP tspgets(SEXP vec, SEXP val)
{
    double start, end, frequency;
    int n;

    if (vec == R_NilValue)
    error(_("attempt to set an attribute on NULL"));

    if(IS_S4_OBJECT(vec)) { /* leave validity checking to validObject */
        if (!isNumeric(val)) /* but should have been checked */
        error(_("'tsp' attribute must be numeric")); 
    installAttrib(vec, R_TspSymbol, val);
    return vec;
    }

    if (!isNumeric(val) || length(val) != 3)
    error(_("'tsp' attribute must be numeric of length three"));

    if (isReal(val)) {
    start = REAL(val)[0];
    end = REAL(val)[1];
    frequency = REAL(val)[2];
    }
    else {
    start = (INTEGER(val)[0] == NA_INTEGER) ?
        NA_REAL : INTEGER(val)[0];
    end = (INTEGER(val)[1] == NA_INTEGER) ?
        NA_REAL : INTEGER(val)[1];
    frequency = (INTEGER(val)[2] == NA_INTEGER) ?
        NA_REAL : INTEGER(val)[2];
    }
    if (frequency <= 0) badtsp();
    n = nrows(vec);
    if (n == 0) error(_("cannot assign 'tsp' to zero-length vector"));

    /* FIXME:  1.e-5 should rather be == option('ts.eps') !! */
    if (fabs(end - start - (n - 1)/frequency) > 1.e-5)
    badtsp();

    PROTECT(vec);
    val = allocVector(REALSXP, 3);
    PROTECT(val);
    REAL(val)[0] = start;
    REAL(val)[1] = end;
    REAL(val)[2] = frequency;
    installAttrib(vec, R_TspSymbol, val);
    UNPROTECT(2);
    return vec;
}

static SEXP commentgets(SEXP vec, SEXP comment)
{
    if (vec == R_NilValue)
    error(_("attempt to set an attribute on NULL"));

    if (isNull(comment) || isString(comment)) {
    if (length(comment) <= 0) {
        SET_ATTRIB(vec, stripAttrib(R_CommentSymbol, ATTRIB(vec)));
    }
    else {
        installAttrib(vec, R_CommentSymbol, comment);
    }
    return R_NilValue;
    }
    error(_("attempt to set invalid 'comment' attribute"));
    return R_NilValue;/*- just for -Wall */
}

SEXP attribute_hidden do_commentgets(SEXP call, SEXP op, SEXP args, SEXP env)
{
    checkArity(op, args);
    if (NAMED(CAR(args)) == 2) SETCAR(args, duplicate(CAR(args)));
    if (length(CADR(args)) == 0) SETCADR(args, R_NilValue);
    setAttrib(CAR(args), R_CommentSymbol, CADR(args));
    return CAR(args);
}

SEXP attribute_hidden do_comment(SEXP call, SEXP op, SEXP args, SEXP env)
{
    checkArity(op, args);
    return getAttrib(CAR(args), R_CommentSymbol);
}

SEXP classgets(SEXP vec, SEXP klass)
{
    if (isNull(klass) || isString(klass)) {
    if (length(klass) <= 0) {
        SET_ATTRIB(vec, stripAttrib(R_ClassSymbol, ATTRIB(vec)));
        SET_OBJECT(vec, 0);
    }
    else {
        /* When data frames were a special data type */
        /* we had more exhaustive checks here.  Now that */
        /* use JMCs interpreted code, we don't need this */
        /* FIXME : The whole "classgets" may as well die. */

        /* HOWEVER, it is the way that the object bit gets set/unset */

        int i;
        Rboolean isfactor = FALSE;

        if (vec == R_NilValue)
        error(_("attempt to set an attribute on NULL"));

        for(i = 0; i < length(klass); i++)
        if(streql(CHAR(STRING_ELT(klass, i)), "factor")) { /* ASCII */
            isfactor = TRUE;
            break;
        }
        if(isfactor && TYPEOF(vec) != INTSXP) {
        /* we cannot coerce vec here, so just fail */
        error(_("adding class \"factor\" to an invalid object"));
        }

        installAttrib(vec, R_ClassSymbol, klass);
        SET_OBJECT(vec, 1);
    }
    return R_NilValue;
    }
    error(_("attempt to set invalid 'class' attribute"));
    return R_NilValue;/*- just for -Wall */
}

/* oldClass() : */
SEXP attribute_hidden do_classgets(SEXP call, SEXP op, SEXP args, SEXP env)
{
    checkArity(op, args);
    if (NAMED(CAR(args)) == 2) SETCAR(args, duplicate(CAR(args)));
    if (length(CADR(args)) == 0) SETCADR(args, R_NilValue);
    setAttrib(CAR(args), R_ClassSymbol, CADR(args));
    return CAR(args);
}

SEXP attribute_hidden do_class(SEXP call, SEXP op, SEXP args, SEXP env)
{
    checkArity(op, args);
    return getAttrib(CAR(args), R_ClassSymbol);
}

/* character elements corresponding to the syntactic types in the
   grammar */
static SEXP lang2str(SEXP obj, SEXPTYPE t)
{
  SEXP symb = CAR(obj);
  static SEXP if_sym = 0, while_sym, for_sym, eq_sym, gets_sym,
    lpar_sym, lbrace_sym, call_sym;
  if(!if_sym) {
    /* initialize:  another place for a hash table */
    if_sym = install("if");
    while_sym = install("while");
    for_sym = install("for");
    eq_sym = install("=");
    gets_sym = install("<-");
    lpar_sym = install("(");
    lbrace_sym = install("{");
    call_sym = install("call");
  }
  if(isSymbol(symb)) {
    if(symb == if_sym || symb == for_sym || symb == while_sym ||
       symb == lpar_sym || symb == lbrace_sym ||
       symb == eq_sym || symb == gets_sym)
      return PRINTNAME(symb);
  }
  return PRINTNAME(call_sym);
}

/* the S4-style class: for dispatch required to be a single string;
   for the new class() function;
   if(!singleString) , keeps S3-style multiple classes.
   Called from the methods package, so exposed.
 */
SEXP R_data_class(SEXP obj, Rboolean singleString)
{
    SEXP value, klass = getAttrib(obj, R_ClassSymbol);
    int n = length(klass);
    if(n == 1 || (n > 0 && !singleString))
    return(klass);
    if(n == 0) {
    SEXP dim = getAttrib(obj, R_DimSymbol);
    int nd = length(dim);
    if(nd > 0) {
        if(nd == 2)
        klass = mkChar("matrix");
        else
        klass = mkChar("array");
    }
    else {
      SEXPTYPE t = TYPEOF(obj);
      switch(t) {
      case CLOSXP: case SPECIALSXP: case BUILTINSXP:
        klass = mkChar("function");
        break;
      case REALSXP:
        klass = mkChar("numeric");
        break;
      case SYMSXP:
        klass = mkChar("name");
        break;
      case LANGSXP:
        klass = lang2str(obj, t);
        break;
      default:
        klass = type2str(t);
      }
    }
    }
    else
    klass = asChar(klass);
    PROTECT(klass);
    value = ScalarString(klass);
    UNPROTECT(1);
    return value;
}

static SEXP s_dot_S3Class;
/* Version for S3-dispatch */
SEXP attribute_hidden R_data_class2 (SEXP obj)
{
    SEXP klass = getAttrib(obj, R_ClassSymbol);
      if(length(klass) > 0) {
    if(IS_S4_OBJECT(obj)) {  /* try for an S4 object with an S3Class slot */
        SEXP S3Class = getAttrib(obj, s_dot_S3Class);
        if(S3Class != R_NilValue)
                klass = S3Class;
    }
    return(klass);
    }
    else {
    SEXPTYPE t;
    SEXP value, class0 = R_NilValue, dim = getAttrib(obj, R_DimSymbol);
    int n = length(dim);
    if(n > 0) {
        if(n == 2)
        class0 = mkChar("matrix");
        else
        class0 = mkChar("array");
    }
    PROTECT(class0);
    switch(t = TYPEOF(obj)) {
    case CLOSXP: case SPECIALSXP: case BUILTINSXP:
        klass = mkChar("function");
        break;
    case INTSXP:
    case REALSXP:
        if(isNull(class0)) {
        PROTECT(value = allocVector(STRSXP, 2));
        SET_STRING_ELT(value, 0, type2str(t));
        SET_STRING_ELT(value, 1, mkChar("numeric"));
        UNPROTECT(2);
        }
        else {
        PROTECT(value = allocVector(STRSXP, 3));
        SET_STRING_ELT(value, 0, class0);
        SET_STRING_ELT(value, 1, type2str(t));
        SET_STRING_ELT(value, 2, mkChar("numeric"));
        UNPROTECT(2);
        }
        return value;
        break;
    case SYMSXP:
        klass = mkChar("name");
        break;
    case LANGSXP:
        klass = lang2str(obj, t);
        break;
    default:
        klass = type2str(t);
    }
    PROTECT(klass);
    if(isNull(class0)) {
        value = ScalarString(klass);
    } else {
        value = allocVector(STRSXP, 2);
        SET_STRING_ELT(value, 0, class0);
        SET_STRING_ELT(value, 1, klass);
    }
    UNPROTECT(2);
    return value;
    }
}

/* class() : */
SEXP attribute_hidden R_do_data_class(SEXP call, SEXP op, SEXP args, SEXP env)
{
  checkArity(op, args);
  return R_data_class(CAR(args), FALSE);
}

/* names(object) <- name */
SEXP attribute_hidden do_namesgets(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP ans;
    checkArity(op, args);
    if (DispatchOrEval(call, op, "names<-", args, env, &ans, 0, 1))
    return(ans);
    PROTECT(args = ans);
    if (NAMED(CAR(args)) == 2)
    SETCAR(args, duplicate(CAR(args)));
    if (CADR(args) != R_NilValue) {
    PROTECT(call = allocList(2));
    SET_TYPEOF(call, LANGSXP);
    SETCAR(call, install("as.character"));
    SETCADR(call, CADR(args));
    SETCADR(args, eval(call, env));
    UNPROTECT(1);
    }
    setAttrib(CAR(args), R_NamesSymbol, CADR(args));
    UNPROTECT(1);
    return CAR(args);
}

SEXP namesgets(SEXP vec, SEXP val)
{
    int i;
    SEXP s, rval, tval;

    PROTECT(vec);
    PROTECT(val);

    /* Ensure that the labels are indeed */
    /* a vector of character strings */

    if (isList(val)) {
    if (!isVectorizable(val))
        error(_("incompatible 'names' argument"));
    else {
        rval = allocVector(STRSXP, length(vec));
        PROTECT(rval);
        /* See PR#10807 */
        for (i = 0, tval = val;
         i < length(vec) && tval != R_NilValue;
         i++, tval = CDR(tval)) {
        s = coerceVector(CAR(tval), STRSXP);
        SET_STRING_ELT(rval, i, STRING_ELT(s, 0));
        }
        UNPROTECT(1);
        val = rval;
    }
    } else val = coerceVector(val, STRSXP);
    UNPROTECT(1);
    PROTECT(val);

    /* Check that the lengths and types are compatible */

    if (length(val) < length(vec)) {
    val = lengthgets(val, length(vec));
    UNPROTECT(1);
    PROTECT(val);
    }

    checkNames(vec, val);

    /* Special treatment for one dimensional arrays */

    if (isVector(vec) || isList(vec) || isLanguage(vec)) {
    s = getAttrib(vec, R_DimSymbol);
    if (TYPEOF(s) == INTSXP && length(s) == 1) {
        PROTECT(val = CONS(val, R_NilValue));
        setAttrib(vec, R_DimNamesSymbol, val);
        UNPROTECT(3);
        return vec;
    }
    }

    if (isList(vec) || isLanguage(vec)) {
    /* Cons-cell based objects */
    i = 0;
    for (s = vec; s != R_NilValue; s = CDR(s), i++)
        if (STRING_ELT(val, i) != R_NilValue
        && STRING_ELT(val, i) != R_NaString
        && *CHAR(STRING_ELT(val, i)) != 0) /* test of length */
        SET_TAG(s, install(translateChar(STRING_ELT(val, i))));
        else
        SET_TAG(s, R_NilValue);
    }
    else if (isVector(vec) || IS_S4_OBJECT(vec))
    /* Normal case */
    installAttrib(vec, R_NamesSymbol, val);
    else
    error(_("invalid type (%s) to set 'names' attribute"),
          type2char(TYPEOF(vec)));
    UNPROTECT(2);
    return vec;
}

SEXP attribute_hidden do_names(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP ans;
    checkArity(op, args);
    if (DispatchOrEval(call, op, "names", args, env, &ans, 0, 1))
    return(ans);
    PROTECT(args = ans);
    ans = CAR(args);
    if (isVector(ans) || isList(ans) || isLanguage(ans))
    ans = getAttrib(ans, R_NamesSymbol);
    else ans =  R_NilValue;
    UNPROTECT(1);
    return ans;
}

SEXP attribute_hidden do_dimnamesgets(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP ans;
    checkArity(op, args);
    if (DispatchOrEval(call, op, "dimnames<-", args, env, &ans, 0, 1))
    return(ans);
    PROTECT(args = ans);
    if (NAMED(CAR(args)) > 1) SETCAR(args, duplicate(CAR(args)));
    setAttrib(CAR(args), R_DimNamesSymbol, CADR(args));
    UNPROTECT(1);
    return CAR(args);
}

static SEXP dimnamesgets1(SEXP val1)
{
    SEXP this2;

    if (LENGTH(val1) == 0) return R_NilValue;
    /* if (isObject(val1)) dispatch on as.character.foo, but we don't
       have the context at this point to do so */
    if (inherits(val1, "factor")) { /* mimic as.character.factor */
    int i, n = LENGTH(val1);
    SEXP labels = getAttrib(val1, install("levels"));
    PROTECT(this2 = allocVector(STRSXP, n));
    for(i = 0; i < n; i++) {
        int ii = INTEGER(val1)[i];
        SET_STRING_ELT(this2, i,
               (ii == NA_INTEGER) ? NA_STRING
               : STRING_ELT(labels, ii - 1));
    }
    UNPROTECT(1);
    return this2;
    }
    if (!isString(val1)) { /* mimic as.character.default */
    PROTECT(this2 = coerceVector(val1, STRSXP));
    SET_ATTRIB(this2, R_NilValue);
    SET_OBJECT(this2, 0);
    UNPROTECT(1);
    return this2;
    }
    return val1;
}


SEXP dimnamesgets(SEXP vec, SEXP val)
{
    SEXP dims, top, newval;
    int i, k;

    PROTECT(vec);
    PROTECT(val);

    if (!isArray(vec) && !isList(vec))
    error(_("'dimnames' applied to non-array"));
    /* This is probably overkill, but you never know; */
    /* there may be old pair-lists out there */
    /* There are, when this gets used as names<- for 1-d arrays */
    if (!isPairList(val) && !isNewList(val))
    error(_("'dimnames' must be a list"));
    dims = getAttrib(vec, R_DimSymbol);
    if ((k = LENGTH(dims)) < length(val))
    error(_("length of 'dimnames' [%d] must match that of 'dims' [%d]"),
          length(val), k);
    if (length(val) == 0) {
    removeAttrib(vec, R_DimNamesSymbol);
    UNPROTECT(2);
    return vec;
    }
    /* Old list to new list */
    if (isList(val)) {
    newval = allocVector(VECSXP, k);
    for (i = 0; i < k; i++) {
        SET_VECTOR_ELT(newval, i, CAR(val));
        val = CDR(val);
    }
    UNPROTECT(1);
    PROTECT(val = newval);
    }
    if (length(val) > 0 && length(val) < k) {
    newval = lengthgets(val, k);
    UNPROTECT(1);
    PROTECT(val = newval);
    }
    if (k != length(val))
    error(_("length of 'dimnames' [%d] must match that of 'dims' [%d]"),
          length(val), k);
    for (i = 0; i < k; i++) {
    SEXP _this = VECTOR_ELT(val, i);
    if (_this != R_NilValue) {
        if (!isVector(_this))
        error(_("invalid type (%s) for 'dimnames' (must be a vector)"),
              type2char(TYPEOF(_this)));
        if (INTEGER(dims)[i] != LENGTH(_this) && LENGTH(_this) != 0)
        error(_("length of 'dimnames' [%d] not equal to array extent"),
              i+1);
        SET_VECTOR_ELT(val, i, dimnamesgets1(_this));
    }
    }
    installAttrib(vec, R_DimNamesSymbol, val);
    if (isList(vec) && k == 1) {
    top = VECTOR_ELT(val, 0);
    i = 0;
    for (val = vec; !isNull(val); val = CDR(val))
        SET_TAG(val, install(translateChar(STRING_ELT(top, i++))));
    }
    UNPROTECT(2);
    return vec;
}

SEXP attribute_hidden do_dimnames(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP ans;
    checkArity(op, args);
    if (DispatchOrEval(call, op, "dimnames", args, env, &ans, 0, 1))
    return(ans);
    PROTECT(args = ans);
    ans = getAttrib(CAR(args), R_DimNamesSymbol);
    UNPROTECT(1);
    return ans;
}

SEXP attribute_hidden do_dim(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP ans;
    checkArity(op, args);
    if (DispatchOrEval(call, op, "dim", args, env, &ans, 0, 1))
    return(ans);
    PROTECT(args = ans);
    ans = getAttrib(CAR(args), R_DimSymbol);
    UNPROTECT(1);
    return ans;
}

SEXP attribute_hidden do_dimgets(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP ans;
    checkArity(op, args);
    if (DispatchOrEval(call, op, "dim<-", args, env, &ans, 0, 1))
    return(ans);
    PROTECT(args = ans);
    if (NAMED(CAR(args)) > 1) SETCAR(args, duplicate(CAR(args)));
    setAttrib(CAR(args), R_DimSymbol, CADR(args));
    setAttrib(CAR(args), R_NamesSymbol, R_NilValue);
    UNPROTECT(1);
    return CAR(args);
}

SEXP dimgets(SEXP vec, SEXP val)
{
    int len, ndim, i, total;
    PROTECT(vec);
    PROTECT(val);
    if ((!isVector(vec) && !isList(vec)))
    error(_("invalid first argument"));

    if (!isVector(val) && !isList(val))
    error(_("invalid second argument"));
    val = coerceVector(val, INTSXP);
    UNPROTECT(1);
    PROTECT(val);

    len = length(vec);
    ndim = length(val);
    if (ndim == 0)
    error(_("length-0 dimension vector is invalid"));
    total = 1;
    for (i = 0; i < ndim; i++)
    total *= INTEGER(val)[i];
    if (total != len)
    error(_("dims [product %d] do not match the length of object [%d]"), total, len);
    removeAttrib(vec, R_DimNamesSymbol);
    installAttrib(vec, R_DimSymbol, val);
    UNPROTECT(2);
    return vec;
}

SEXP attribute_hidden do_attributes(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP attrs, names, namesattr, value;
    int nvalues;
    namesattr = R_NilValue;
    attrs = ATTRIB(CAR(args));
    nvalues = length(attrs);
    if (isList(CAR(args))) {
    namesattr = getAttrib(CAR(args), R_NamesSymbol);
    if (namesattr != R_NilValue)
        nvalues++;
    }
    /* FIXME */
    if (nvalues <= 0)
    return R_NilValue;
    /* FIXME */
    PROTECT(namesattr);
    PROTECT(value = allocVector(VECSXP, nvalues));
    PROTECT(names = allocVector(STRSXP, nvalues));
    nvalues = 0;
    if (namesattr != R_NilValue) {
    SET_VECTOR_ELT(value, nvalues, namesattr);
    SET_STRING_ELT(names, nvalues, PRINTNAME(R_NamesSymbol));
    nvalues++;
    }
    while (attrs != R_NilValue) {
    /* treat R_RowNamesSymbol specially */
    if (TAG(attrs) == R_RowNamesSymbol)
        SET_VECTOR_ELT(value, nvalues,
               getAttrib(CAR(args), R_RowNamesSymbol));
    else
        SET_VECTOR_ELT(value, nvalues, CAR(attrs));
    if (TAG(attrs) == R_NilValue)
        SET_STRING_ELT(names, nvalues, R_BlankString);
    else
        SET_STRING_ELT(names, nvalues, PRINTNAME(TAG(attrs)));
    attrs = CDR(attrs);
    nvalues++;
    }
    setAttrib(value, R_NamesSymbol, names);
    SET_NAMED(value, NAMED(CAR(args)));
    UNPROTECT(3);
    return value;
}

SEXP attribute_hidden do_levelsgets(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP ans;
    checkArity(op, args);
    if (DispatchOrEval(call, op, "levels<-", args, env, &ans, 0, 1))
    return(ans);
    PROTECT(args = ans);
    if (NAMED(CAR(args)) > 1) SETCAR(args, duplicate(CAR(args)));
    setAttrib(CAR(args), R_LevelsSymbol, CADR(args));
    UNPROTECT(1);
    return CAR(args);
}

/* attributes(object) <- attrs */
SEXP attribute_hidden do_attributesgets(SEXP call, SEXP op, SEXP args, SEXP env)
{
/* NOTE: The following code ensures that when an attribute list */
/* is attached to an object, that the "dim" attibute is always */
/* brought to the front of the list.  This ensures that when both */
/* "dim" and "dimnames" are set that the "dim" is attached first. */

    SEXP object, attrs, names = R_NilValue /* -Wall */;
    int i, i0 = -1, nattrs;

    /* Extract the arguments from the argument list */

    object = CAR(args);
    attrs = CADR(args);

    /* Do checks before duplication */
    if (!isNewList(attrs))
    error(_("attributes must be a list or NULL"));
    nattrs = length(attrs);
    if (nattrs > 0) {
    names = getAttrib(attrs, R_NamesSymbol);
    if (names == R_NilValue)
        error(_("attributes must be named"));
    for (i = 1; i < nattrs; i++) {
        if (STRING_ELT(names, i) == R_NilValue ||
        CHAR(STRING_ELT(names, i))[0] == '\0') { /* all ASCII tests */
        error(_("all attributes must have names [%d does not]"), i+1);
        }
    }
    }

    if (object == R_NilValue) {
    if (attrs == R_NilValue)
        return R_NilValue;
    else
        PROTECT(object = allocVector(VECSXP, 0));
    } else {
    /* Unlikely to have NAMED == 0 here.
       As from R 2.7.0 we don't optimize NAMED == 1 _if_ we are
       setting any attributes as an error later on would leave
       'obj' changed */
    if (NAMED(object) > 1 || (NAMED(object) == 1 && nattrs))
        object = duplicate(object);
    PROTECT(object);
    }


    /* Empty the existing attribute list */

    /* FIXME: the code below treats pair-based structures */
    /* in a special way.  This can probably be dropped down */
    /* the road (users should never encounter pair-based lists). */
    /* Of course, if we want backward compatibility we can't */
    /* make the change. :-( */

    if (isList(object))
    setAttrib(object, R_NamesSymbol, R_NilValue);
    SET_ATTRIB(object, R_NilValue);
    /* We have just removed the class, but might reset it later */
    SET_OBJECT(object, 0);
    /* Probably need to fix up S4 bit in other cases, but
       definitely in this one */
    if(nattrs == 0) UNSET_S4_OBJECT(object);

    /* We do two passes through the attributes; the first */
    /* finding and transferring "dim" and the second */
    /* transferring the rest.  This is to ensure that */
    /* "dim" occurs in the attribute list before "dimnames". */

    if (nattrs > 0) {
    for (i = 0; i < nattrs; i++) {
        if (!strcmp(CHAR(STRING_ELT(names, i)), "dim")) {
        i0 = i;
        setAttrib(object, R_DimSymbol, VECTOR_ELT(attrs, i));
        break;
        }
    }
    for (i = 0; i < nattrs; i++) {
        if (i == i0) continue;
        setAttrib(object, install(translateChar(STRING_ELT(names, i))),
              VECTOR_ELT(attrs, i));
    }
    }
    UNPROTECT(1);
    return object;
}

/*  This code replaces an R function defined as

    attr <- function (x, which)
    {
    if (!is.character(which))
        stop("attribute name must be of mode character")
    if (length(which) != 1)
        stop("exactly one attribute name must be given")
    attributes(x)[[which]]
   }

The R functions was being called very often and replacing it by
something more efficient made a noticeable difference on several
benchmarks.  There is still some inefficiency since using getAttrib
means the attributes list will be searched twice, but this seems
fairly minor.  LT */

SEXP attribute_hidden do_attr(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP s, t, tag = R_NilValue, alist;
    const char *str;
    int n, nargs = length(args), exact = 0;
    enum { NONE, PARTIAL, PARTIAL2, FULL } match = NONE;

    if (nargs < 2 || nargs > 3)
    errorcall(call, "either 2 or 3 arguments are required");

    s = CAR(args);
    t = CADR(args);
    if(nargs == 3) {
    exact = asLogical(CADDR(args));
    if(exact == NA_LOGICAL) exact = 0;
    }

    if (!isString(t))
    errorcall(call, _("'which' must be of mode character"));
    if (length(t) != 1)
    errorcall(call, _("exactly one attribute 'which' must be given"));

    if(STRING_ELT(t, 0) == NA_STRING) return R_NilValue;
    str = translateChar(STRING_ELT(t, 0));
    n = strlen(str);

    /* try to find a match among the attributes list */
    for (alist = ATTRIB(s); alist != R_NilValue; alist = CDR(alist)) {
    SEXP tmp = TAG(alist);
    const char *s = CHAR(PRINTNAME(tmp));
    if (! strncmp(s, str, n)) {
        if (strlen(s) == n) {
        tag = tmp;
        match = FULL;
        break;
        }
        else if (match == PARTIAL || match == PARTIAL2) {
        /* this match is partial and we already have a partial match,
           so the query is ambiguous and we will return R_NilValue
           unless a full match comes up.
        */
        match = PARTIAL2;
        } else {
        tag = tmp;
        match = PARTIAL;
        }
    }
    }
    if (match == PARTIAL2) return R_NilValue;

    /* Unless a full match has been found, check for a "names" attribute.
       This is stored via TAGs on pairlists, and via rownames on 1D arrays.
    */
    if (match != FULL && strncmp("names", str, n) == 0) {
    if (strlen("names") == n) {
        /* we have a full match on "names", if there is such an
           attribute */
        tag = R_NamesSymbol;
        match = FULL;
    }
    else if (match == NONE && !exact) {
        /* no match on other attributes and a possible
           partial match on "names" */
        tag = R_NamesSymbol;
        t = getAttrib(s, tag);
        if(t != R_NilValue && R_warn_partial_match_attr)
        warningcall(call, _("partial match of '%s' to '%s'"), str,
                CHAR(PRINTNAME(tag)));
        return t;
    }
    else if (match == PARTIAL && strcmp(CHAR(PRINTNAME(tag)), "names")) {
        /* There is a possible partial match on "names" and on another
           attribute. If there really is a "names" attribute, then the
           query is ambiguous and we return R_NilValue.  If there is no
           "names" attribute, then the partially matched one, which is
           the current value of tag, can be used. */
        if (getAttrib(s, R_NamesSymbol) != R_NilValue)
        return R_NilValue;
    }
    }

    if (match == NONE  || (exact && match != FULL))
    return R_NilValue;
    if (match == PARTIAL && R_warn_partial_match_attr)
    warningcall(call, _("partial match of '%s' to '%s'"), str,
            CHAR(PRINTNAME(tag)));

    return getAttrib(s, tag);
}

SEXP attribute_hidden do_attrgets(SEXP call, SEXP op, SEXP args, SEXP env)
{
    /*  attr(obj, "<name>")  <-  value  */
    SEXP obj, name;

    obj = CAR(args);
    if (NAMED(obj) == 2)
    PROTECT(obj = duplicate(obj));
    else
    PROTECT(obj);

    name = CADR(args);
    if (!isValidString(name) || STRING_ELT(name, 0) == NA_STRING)
    error(_("'name' must be non-null character string"));
    setAttrib(obj, name, CADDR(args));
    UNPROTECT(1);
    return obj;
}


/* These provide useful shortcuts which give access to */
/* the dimnames for matrices and arrays in a standard form. */

void GetMatrixDimnames(SEXP x, SEXP *rl, SEXP *cl,
               const char **rn, const char **cn)
{
    SEXP dimnames = getAttrib(x, R_DimNamesSymbol);
    SEXP nn;

    if (isNull(dimnames)) {
    *rl = R_NilValue;
    *cl = R_NilValue;
    *rn = NULL;
    *cn = NULL;
    }
    else {
    *rl = VECTOR_ELT(dimnames, 0);
    *cl = VECTOR_ELT(dimnames, 1);
    nn = getAttrib(dimnames, R_NamesSymbol);
    if (isNull(nn)) {
        *rn = NULL;
        *cn = NULL;
    }
    else {
        *rn = translateChar(STRING_ELT(nn, 0));
        *cn = translateChar(STRING_ELT(nn, 1));
    }
    }
}


SEXP GetArrayDimnames(SEXP x)
{
    return getAttrib(x, R_DimNamesSymbol);
}


/* the code to manage slots in formal classes. These are attributes,
   but without partial matching and enforcing legal slot names (it's
   an error to get a slot that doesn't exist. */


static SEXP pseudo_NULL = 0;

static SEXP s_dot_Data;
static SEXP s_getDataPart;
static SEXP s_setDataPart;

static void init_slot_handling(void) {
    s_dot_Data = install(".Data");
    s_dot_S3Class = install(".S3Class");
    s_getDataPart = install("getDataPart");
    s_setDataPart = install("setDataPart");
    /* create and preserve an object that is NOT R_NilValue, and is used
       to represent slots that are NULL (which an attribute can not
       be).  The point is not just to store NULL as a slot, but also to
       provide a check on invalid slot names (see get_slot below).

       The object has to be a symbol if we're going to check identity by
       just looking at referential equality. */
    pseudo_NULL = install("\001NULL\001");
}

static SEXP data_part(SEXP obj) {
    SEXP e, val;
    if(!s_getDataPart)
    init_slot_handling();
    PROTECT(e = allocVector(LANGSXP, 2));
    SETCAR(e, s_getDataPart);
    val = CDR(e);
    SETCAR(val, obj);
    val = eval(e, R_MethodsNamespace);
    UNSET_S4_OBJECT(val); /* data part must be base vector */
    UNPROTECT(1);
    return(val);
}

static SEXP set_data_part(SEXP obj,  SEXP rhs) {
    SEXP e, val;
    if(!s_setDataPart)
    init_slot_handling();
    PROTECT(e = allocVector(LANGSXP, 3));
    SETCAR(e, s_setDataPart);
    val = CDR(e);
    SETCAR(val, obj);
    val = CDR(val);
    SETCAR(val, rhs);
    val = eval(e, R_MethodsNamespace);
    SET_S4_OBJECT(val);
    UNPROTECT(1);
    return(val);
}

/* Slots are stored as attributes to
   provide some back-compatibility
*/

/**
 * R_has_slot() : a C-level test if a obj@<name> is available;
 *                as R_do_slot() gives an error when there's no such slot.
 */
int R_has_slot(SEXP obj, SEXP name) {

#define R_SLOT_INIT                         \
    if(!(isSymbol(name) || (isString(name) && LENGTH(name) == 1)))  \
    error(_("invalid type or length for slot name"));       \
    if(!s_dot_Data)                         \
    init_slot_handling();                       \
    if(isString(name)) name = install(CHAR(STRING_ELT(name, 0)))

    R_SLOT_INIT;
    if(name == s_dot_Data)
    return(1);
    /* else */
    return(getAttrib(obj, name) != R_NilValue);
}

SEXP R_do_slot(SEXP obj, SEXP name) {
    R_SLOT_INIT;
    if(name == s_dot_Data)
    return data_part(obj);
    else {
    SEXP value = getAttrib(obj, name);
    if(value == R_NilValue) {
        SEXP input = name, classString;
        if(name == s_dot_S3Class) /* defaults to class(obj) */
            return R_data_class(obj, FALSE);
        if(isSymbol(name) ) {
        input = PROTECT(ScalarString(PRINTNAME(name)));
        classString = getAttrib(obj, R_ClassSymbol);
        if(isNull(classString)) {
            UNPROTECT(1);
            error(_("cannot get a slot (\"%s\") from an object of type \"%s\""),
              translateChar(asChar(input)),
              CHAR(type2str(TYPEOF(obj))));
        }
        }
        else classString = R_NilValue; /* make sure it is initialized */
        /* not there.  But since even NULL really does get stored, this
           implies that there is no slot of this name.  Or somebody
           screwed up by using attr(..) <- NULL */

        UNPROTECT(1);
        error(_("no slot of name \"%s\" for this object of class \"%s\""),
          translateChar(asChar(input)),
          translateChar(asChar(classString)));
    }
    else if(value == pseudo_NULL)
        value = R_NilValue;
    return value;
    }
}
#undef R_SLOT_INIT

SEXP R_do_slot_assign(SEXP obj, SEXP name, SEXP value) {
    PROTECT(obj); PROTECT(value);
                /* Ensure that name is a symbol */
    if(isString(name) && LENGTH(name) == 1)
    name = install(translateChar(STRING_ELT(name, 0)));
    if(TYPEOF(name) == CHARSXP)
    name = install(translateChar(name));
    if(!isSymbol(name) )
    error(_("invalid type or length for slot name"));

    if(!s_dot_Data)     /* initialize */
    init_slot_handling();

    if(name == s_dot_Data) {    /* special handling */
    obj = set_data_part(obj, value);
    UNPROTECT(2);
    return obj;
    }
    if(isNull(value))       /* Slots, but not attributes, can be NULL.*/
    value = pseudo_NULL;    /* Store a special symbol instead. */

    setAttrib(obj, name, value);
    UNPROTECT(2);
    return obj;
}

#ifdef UNUSED
SEXP R_pseudo_null() {
    if(pseudo_NULL == 0)
    init_slot_handling();
    return pseudo_NULL;
}
#endif


/* the @ operator, and its assignment form.  Processed much like $
   (see do_subset3) but without S3-style methods.
*/
SEXP attribute_hidden do_AT(SEXP call, SEXP op, SEXP args, SEXP env)
{
    SEXP  nlist, object, ans, klass;

    if(!isMethodsDispatchOn())
    error(_("formal classes cannot be used without the methods package"));
    nlist = CADR(args);
    /* Do some checks here -- repeated in R_do_slot, but on repeat the
     * test expression should kick out on the first element. */
    if(!(isSymbol(nlist) || (isString(nlist) && LENGTH(nlist) == 1)))
    error(_("invalid type or length for slot name"));
    if(isString(nlist)) nlist = install(translateChar(STRING_ELT(nlist, 0)));
    PROTECT(object = eval(CAR(args), env));
    if(!s_dot_Data) init_slot_handling();
    if(nlist != s_dot_Data && !IS_S4_OBJECT(object)) {
    klass = getAttrib(object, R_ClassSymbol);
    if(length(klass) == 0)
        error(_("trying to get slot \"%s\" from an object of a basic class (\"%s\") with no slots"),
          CHAR(PRINTNAME(nlist)),
          CHAR(STRING_ELT(R_data_class(object, FALSE), 0)));
    else
        error(_("trying to get slot \"%s\" from an object (class \"%s\") that is not an S4 object "),
          CHAR(PRINTNAME(nlist)),
          translateChar(STRING_ELT(klass, 0)));
    }

    ans = R_do_slot(object, nlist);
    UNPROTECT(1);
    return ans;
}