/*
 *  R : A Computer Language for Statistical Data Analysis
 *  Copyright (C) 1995-1998  Robert Gentleman and Ross Ihaka
 *  Copyright (C) 1999-2006  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, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street Fifth Floor, Boston, MA 02110-1301  USA
 */

/* <UTF8> char here is handled as a whole string, 
   except that there is an assumption that filesep is one byte.
*/

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

#include <Defn.h>
#include <Print.h>
#include <Fileio.h>
#include <Rconnections.h>

static R_len_t asVecSize(SEXP x)
{
    int warn = 0, res;
    double d;

    if (isVectorAtomic(x) && LENGTH(x) >= 1) {
	switch (TYPEOF(x)) {
	case LGLSXP:
	    res = IntegerFromLogical(LOGICAL(x)[0], &warn);
	    if(res == NA_INTEGER) error(_("vector size cannot be NA"));
	    return res;
	case INTSXP:
	    res = INTEGER(x)[0];
	    if(res == NA_INTEGER) error(_("vector size cannot be NA"));
	    return res;
	case REALSXP:
	    d = REAL(x)[0];
	    if(d < 0) error(_("vector size cannot be negative"));
	    if(d > R_LEN_T_MAX) error(_("vector size specified is too large"));
	    return (R_size_t) d;
	default:
	    UNIMPLEMENTED_TYPE("asVecSize", x);
	}
    }
    return -1;
}

SEXP attribute_hidden do_delay(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP expr, env;
    checkArity(op, args);
    expr = CAR(args);
    env = eval(CADR(args), rho);
    if (isNull(env)) {
	error(_("use of NULL environment is defunct"));
	env = R_BaseEnv;
    } else    
    if (!isEnvironment(env))
	errorcall(call, R_MSG_IA);
    return mkPROMISE(expr, env);
}

SEXP attribute_hidden do_delayed(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP name = R_NilValue /* -Wall */, expr, eenv, aenv;
    checkArity(op, args);
    
    if (!isString(CAR(args)) || length(CAR(args)) == 0)
    	errorcall(call, _("invalid first argument"));
    else
	name = install(CHAR(STRING_ELT(CAR(args), 0)));
    args = CDR(args);
    expr = CAR(args);
    
    args = CDR(args);
    eenv = CAR(args);
    if (isNull(eenv)) {
	error(_("use of NULL environment is defunct"));
	eenv = R_BaseEnv;
    } else
    if (!isEnvironment(eenv))
	errorcall(call, R_MSG_IA);
	
    args = CDR(args);
    aenv = CAR(args);
    if (isNull(aenv)) {
	error(_("use of NULL environment is defunct"));
	aenv = R_BaseEnv;
    } else
    if (!isEnvironment(aenv))
    	errorcall(call, R_MSG_IA);
    	
    defineVar(name, mkPROMISE(expr, eenv), aenv);
    return R_NilValue;
}

SEXP attribute_hidden do_onexit(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    RCNTXT *ctxt;
    SEXP code, add, oldcode, tmp;
    int addit = 0;

    switch (length(args)) {
    case 0:
	code = R_NilValue;
	break;
    case 1:
	code = CAR(args);
	break;
    case 2:
	code = CAR(args);
	add = eval(CADR(args), rho);
	if ( TYPEOF(add) != LGLSXP || length(add) != 1 )
	    errorcall(call, _("invalid '%s' argument"), "add");
	addit = (LOGICAL(add)[0] == 1);
	break;
    default:
	errorcall_return(call, _("invalid number of arguments"));
    }
    ctxt = R_GlobalContext;
    while (ctxt != R_ToplevelContext && !(ctxt->callflag & CTXT_FUNCTION) )
	ctxt = ctxt->nextcontext;
    if (ctxt->callflag & CTXT_FUNCTION)
    {
	if (addit && (oldcode = ctxt->conexit) != R_NilValue ) {
	    if ( CAR(oldcode) != R_BraceSymbol )
	    {
		PROTECT(tmp = allocList(3));
		SETCAR(tmp, R_BraceSymbol);
		SETCADR(tmp, oldcode);
		SETCADDR(tmp, code);
		SET_TYPEOF(tmp, LANGSXP);
		ctxt->conexit = tmp;
		UNPROTECT(1);
	    }
	    else
	    {
		PROTECT(tmp=allocList(1));
		SETCAR(tmp, code);
		ctxt->conexit = listAppend(duplicate(oldcode),tmp);
		UNPROTECT(1);
	    }
	}
	else
	    ctxt->conexit = code;
    }
    return R_NilValue;
}

SEXP attribute_hidden do_args(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP s;
    checkArity(op,args);
    if (TYPEOF(CAR(args)) == STRSXP && length(CAR(args))==1) {
	PROTECT(s = install(CHAR(STRING_ELT(CAR(args), 0))));
	SETCAR(args, findFun(s, rho));
	UNPROTECT(1);
    }
    if (TYPEOF(CAR(args)) == CLOSXP) {
	s = allocSExp(CLOSXP);
	SET_FORMALS(s, FORMALS(CAR(args)));
	SET_BODY(s, R_NilValue);
	SET_CLOENV(s, R_GlobalEnv);
	return(s);
    }
    return R_NilValue;
}

SEXP attribute_hidden do_formals(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    checkArity(op, args);
    if (TYPEOF(CAR(args)) == CLOSXP)
	return duplicate(FORMALS(CAR(args)));
    else
	return R_NilValue;
}

SEXP attribute_hidden do_body(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    checkArity(op, args);
    if (TYPEOF(CAR(args)) == CLOSXP)
	return duplicate(BODY_EXPR(CAR(args)));
    else return R_NilValue;
}

SEXP attribute_hidden do_bodyCode(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    checkArity(op, args);
    if (TYPEOF(CAR(args)) == CLOSXP)
	return duplicate(BODY(CAR(args)));
    else return R_NilValue;
}

SEXP attribute_hidden do_envir(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    checkArity(op, args);
    if (TYPEOF(CAR(args)) == CLOSXP)
	return CLOENV(CAR(args));
    else if (CAR(args) == R_NilValue)
	return R_GlobalContext->sysparent;
    else return getAttrib(CAR(args), R_DotEnvSymbol);
}

SEXP attribute_hidden do_envirgets(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP env, s = CAR(args);
    checkArity(op, args);
    env = CADR(args);

    if (TYPEOF(CAR(args)) == CLOSXP 
        && (isEnvironment(env) || isNull(env))) {
	if (isNull(env))
	    error(_("use of NULL environment is defunct"));
	if(NAMED(s) > 1) {
	    /* partial duplicate */
	    s = allocSExp(CLOSXP);
	    SET_FORMALS(s, FORMALS(CAR(args)));
	    SET_BODY(s, BODY(CAR(args)));
	}
	SET_CLOENV(s, env);
    }
    else if (isNull(env) || isEnvironment(env))
	setAttrib(s, R_DotEnvSymbol, env);
    else
	errorcall(call, _("replacement object is not an environment"));
    return s;
}


SEXP attribute_hidden do_newenv(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP enclos;
    int hash;

    checkArity(op, args);

    hash = asInteger(CAR(args));
    enclos = CADR(args);
    if (isNull(enclos)) {
	error(_("use of NULL environment is defunct"));
	enclos = R_BaseEnv;
    } else    
    if( !isEnvironment(enclos) )
	errorcall(call, _("'enclos' must be an environment"));

    if( hash )
	return R_NewHashedEnv(enclos);
    else
	return NewEnvironment(R_NilValue, R_NilValue, enclos);
}

SEXP attribute_hidden do_parentenv(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    checkArity(op, args);

    if( !isEnvironment(CAR(args)) )
	errorcall(call, _("argument is not an environment"));
    if( CAR(args) == R_EmptyEnv )
    	errorcall(call, _("the empty environment has no parent"));
    return( ENCLOS(CAR(args)) );
}

SEXP attribute_hidden do_parentenvgets(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP env, parent;
    checkArity(op, args);

    env = CAR(args);
    if (isNull(env)) {
	error(_("use of NULL environment is defunct"));
	env = R_BaseEnv;
    } else
    if( !isEnvironment(env) )
	errorcall(call, _("argument is not an environment"));
    if( env == R_EmptyEnv )
    	errorcall(call, _("can not set parent of the empty environment"));
    parent = CADR(args);
    if (isNull(parent)) {
	error(_("use of NULL environment is defunct"));
	parent = R_BaseEnv;
    } else    
    if( !isEnvironment(parent) )
	errorcall(call, _("'parent' is not an environment"));

    SET_ENCLOS(env, parent);

    return( env );
}

static void cat_newline(SEXP labels, int *width, int lablen, int ntot)
{
    Rprintf("\n");
    *width = 0;
    if (labels != R_NilValue) {
	Rprintf("%s ", EncodeString(STRING_ELT(labels, ntot % lablen),
	  	                    1, 0, Rprt_adj_left));
	*width += Rstrlen(STRING_ELT(labels, ntot % lablen), 0) + 1;
    }
}

static void cat_sepwidth(SEXP sep, int *width, int ntot)
{
    if (sep == R_NilValue || LENGTH(sep) == 0)
	*width = 0;
    else
	*width = Rstrlen(STRING_ELT(sep, ntot % LENGTH(sep)), 0);
}

static void cat_printsep(SEXP sep, int ntot)
{
    char *sepchar;
    if (sep == R_NilValue || LENGTH(sep) == 0)
	return;

    sepchar = CHAR(STRING_ELT(sep, ntot % LENGTH(sep)));
    Rprintf("%s",sepchar);
    return;
}

typedef struct cat_info {
    Rboolean wasopen;
    int changedcon;
    Rconnection con;
} cat_info;

static void cat_cleanup(void *data)
{
    cat_info *pci = data;
    Rconnection con = pci->con;
    Rboolean wasopen = pci->wasopen;
    int changedcon = pci->changedcon;

    con->fflush(con);
    if(!wasopen) con->close(con);  /**** do this second? */
    if(changedcon) switch_stdout(-1, 0);
}

SEXP attribute_hidden do_cat(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    cat_info ci;
    RCNTXT cntxt;
    SEXP objs, file, fill, sepr, labs, s;
    int ifile;
    Rconnection con;
    int append;
    int w, i, iobj, n, nobjs, pwidth, width, sepw, lablen, ntot, nlsep, nlines;
    char *p = "", buf[512];

    checkArity(op, args);

    /* Use standard printing defaults */
    PrintDefaults(rho);

    objs = CAR(args);
    args = CDR(args);

    file = CAR(args);
    ifile = asInteger(file);
    con = getConnection(ifile);
    args = CDR(args);

    sepr = CAR(args);
    if (!isString(sepr))
	errorcall(call, _("invalid '%s' specification"), "sep");
    nlsep = 0;
    for (i = 0; i < LENGTH(sepr); i++)
	if (strstr(CHAR(STRING_ELT(sepr, i)), "\n")) nlsep = 1;
    args = CDR(args);

    fill = CAR(args);
    if ((!isNumeric(fill) && !isLogical(fill)) || (length(fill) != 1))
	errorcall(call, _("invalid '%s' argument"), "fill");
    if (isLogical(fill)) {
	if (asLogical(fill) == 1)
	    pwidth = R_print.width;
	else
	    pwidth = INT_MAX;
    }
    else pwidth = asInteger(fill);
    if(pwidth <= 0) {
	warningcall(call, _("non-positive 'fill' argument will be ignored"));
	pwidth = INT_MAX;
    }
    args = CDR(args);

    labs = CAR(args);
    if (!isString(labs) && labs != R_NilValue)
	errorcall(call, _("invalid '%s' argument"), "label");
    lablen = length(labs);
    args = CDR(args);

    append = asLogical(CAR(args));
    if (append == NA_LOGICAL)
	errorcall(call, _("invalid '%s' specification"), "append");

    ci.wasopen = con->isopen;

    ci.changedcon = switch_stdout(ifile, 0);
    /* will open new connection if required */

    ci.con = con;

    /* set up a context which will close the connection if there is an error */
    begincontext(&cntxt, CTXT_CCODE, R_NilValue, R_BaseEnv, R_BaseEnv,
		 R_NilValue, R_NilValue);
    cntxt.cend = &cat_cleanup;
    cntxt.cenddata = &ci;

    nobjs = length(objs);
    width = 0;
    ntot = 0;
    nlines = 0;
    for (iobj = 0; iobj < nobjs; iobj++) {
	s = VECTOR_ELT(objs, iobj);
	if (iobj != 0 && !isNull(s))
	    cat_printsep(sepr, 0);
	n = length(s);
	if (n > 0) {
	    if (labs != R_NilValue && (iobj == 0)
		&& (asInteger(fill) > 0)) {
		Rprintf("%s ", CHAR(STRING_ELT(labs, nlines)));
		width += strlen(CHAR(STRING_ELT(labs, nlines % lablen))) + 1;
		nlines++;
	    }
	    if (isString(s))
		p = CHAR(STRING_ELT(s, 0));
            else if (isSymbol(s))
                p = CHAR(PRINTNAME(s));
	    else if (isVectorAtomic(s)) {
		p = EncodeElement(s, 0, 0, OutDec);
		strcpy(buf,p);
		p=buf;
	    }
#ifdef fixed_cat
	    else if (isVectorList(s)) {
	      /* FIXME:	 call EncodeElement() for every element of  s.

		 Real Problem: `s' can be large;
		 should do line breaking etc.. (buf is of limited size)
	      */
	    }
#endif
	    else
		errorcall(call, 
			  _("argument %d (type '%s') cannot be handled by 'cat'"),
			  1+iobj, type2char(TYPEOF(s)));
	    /* FIXME : cat(...) should handle ANYTHING */
	    w = strlen(p);
	    cat_sepwidth(sepr, &sepw, ntot);
	    if ((iobj > 0) && (width + w + sepw > pwidth)) {
		cat_newline(labs, &width, lablen, nlines);
		nlines++;
	    }
	    for (i = 0; i < n; i++, ntot++) {
		Rprintf("%s", p);
		width += w + sepw;
		if (i < (n - 1)) {
		    cat_printsep(sepr, ntot);
		    if (isString(s))
			p = CHAR(STRING_ELT(s, i+1));
		    else {
			p = EncodeElement(s, i+1, 0, OutDec);
			strcpy(buf,p);
			p = buf;
		    }
		    w = strlen(p);
		    cat_sepwidth(sepr, &sepw, ntot);
		    /* This is inconsistent with the version above.
		       As from R 2.3.0, fill <= 0 is ignored. */
		    if ((width + w + sepw > pwidth) && pwidth) {
			cat_newline(labs, &width, lablen, nlines);
			nlines++;
		    }
		}
	    }
	}
    }
    if ((pwidth != INT_MAX) || nlsep)
	Rprintf("\n");

    /* end the context after anything that could raise an error but before
       doing the cleanup so the cleanup doesn't get done twice */
    endcontext(&cntxt);

    cat_cleanup(&ci);

    return R_NilValue;
}

SEXP attribute_hidden do_makelist(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP list, names;
    int i, n, havenames;
    havenames = 0;
    n = length(args);
    PROTECT(list = allocVector(VECSXP, n));
    PROTECT(names = allocVector(STRSXP, n));
    for (i = 0; i < n; i++) {
	if (TAG(args) != R_NilValue) {
	    SET_STRING_ELT(names, i, PRINTNAME(TAG(args)));
	    havenames = 1;
	}
	else {
	    SET_STRING_ELT(names, i, R_BlankString);
	}
	if (NAMED(CAR(args)))
	    SET_VECTOR_ELT(list, i, duplicate(CAR(args)));
	else
	    SET_VECTOR_ELT(list, i, CAR(args));
	args = CDR(args);
    }
    if (havenames) {
	setAttrib(list, R_NamesSymbol, names);
    }
    UNPROTECT(2);
    return list;
}

SEXP attribute_hidden do_expression(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP a, ans, nms;
    int i, n, named;
    named = 0;
    n = length(args);
    PROTECT(ans = allocVector(EXPRSXP, n));
    a = args;
    for (i = 0; i < n; i++) {
	SET_VECTOR_ELT(ans, i, duplicate(CAR(a)));
	if (TAG(a) != R_NilValue) named = 1;
	a = CDR(a);
    }
    if (named) {
	PROTECT(nms = allocVector(STRSXP, n));
	a = args;
	for (i = 0; i < n; i++) {
	    if (TAG(a) != R_NilValue)
		SET_STRING_ELT(nms, i, PRINTNAME(TAG(a)));
	    else
		SET_STRING_ELT(nms, i, R_BlankString);
	    a = CDR(a);
	}
	setAttrib(ans, R_NamesSymbol, nms);
	UNPROTECT(1);
    }
    UNPROTECT(1);
    return ans;
}

/* vector(mode="logical", length=0) */
SEXP attribute_hidden do_makevector(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    R_len_t len /*, i*/;
    SEXP s;
    SEXPTYPE mode;
    checkArity(op, args);
    len = asVecSize(CADR(args));
    s = coerceVector(CAR(args), STRSXP);
    if (length(s) == 0)
	error(_("vector: zero-length 'type' argument"));
    mode = str2type(CHAR(STRING_ELT(s, 0)));
    if (mode == -1 && streql(CHAR(STRING_ELT(s, 0)), "double"))
	mode = REALSXP;
    switch (mode) {
    case LGLSXP:
    case INTSXP:
    case REALSXP:
    case CPLXSXP:
    case STRSXP:
    case EXPRSXP:
    case VECSXP:
    case RAWSXP:
	s = allocVector(mode, len);
	break;
    case LISTSXP:
	s = allocList(len);
	break;
    default:
	error(_("vector: cannot make a vector of mode \"%s\"."),
	      CHAR(STRING_ELT(s, 0)));
    }
    if (mode == INTSXP || mode == LGLSXP)
	memset(INTEGER(s), 0, len*sizeof(int));
        /*for (i = 0; i < len; i++) INTEGER(s)[i] = 0; */
    else if (mode == REALSXP)
	memset(REAL(s), 0, len*sizeof(double));
	/*for (i = 0; i < len; i++) REAL(s)[i] = 0.;*/
    else if (mode == CPLXSXP)
	memset(COMPLEX(s), 0, len*sizeof(Rcomplex));
    /*
	for (i = 0; i < len; i++) {
	    COMPLEX(s)[i].r = 0.;
	    COMPLEX(s)[i].i = 0.;
	}
    */
    else if (mode == RAWSXP)
	memset(RAW(s), 0, len);
    /* other cases: list/expression have "NULL", ok */
    return s;
}


/* do_lengthgets: assign a length to a vector or a list */
/* (if it is vectorizable). We could probably be fairly */
/* clever with memory here if we wanted to. */

SEXP lengthgets(SEXP x, R_len_t len)
{
    R_len_t lenx, i;
    SEXP rval, names, xnames, t;
    if (!isVector(x) && !isVectorizable(x))
	error(_("cannot set length of non-vector"));
    lenx = length(x);
    if (lenx == len)
	return (x);
    rval = allocVector(TYPEOF(x), len);
    PROTECT(xnames = getAttrib(x, R_NamesSymbol));
    if (xnames != R_NilValue)
	names = allocVector(STRSXP, len);
    else names = R_NilValue;	/*- just for -Wall --- should we do this ? */
    switch (TYPEOF(x)) {
    case NILSXP:
	break;
    case LGLSXP:
    case INTSXP:
	for (i = 0; i < len; i++)
	    if (i < lenx) {
		INTEGER(rval)[i] = INTEGER(x)[i];
		if (xnames != R_NilValue)
		    SET_STRING_ELT(names, i, STRING_ELT(xnames, i));
	    }
	    else
		INTEGER(rval)[i] = NA_INTEGER;
	break;
    case REALSXP:
	for (i = 0; i < len; i++)
	    if (i < lenx) {
		REAL(rval)[i] = REAL(x)[i];
		if (xnames != R_NilValue)
		    SET_STRING_ELT(names, i, STRING_ELT(xnames, i));
	    }
	    else
		REAL(rval)[i] = NA_REAL;
	break;
    case CPLXSXP:
	for (i = 0; i < len; i++)
	    if (i < lenx) {
		COMPLEX(rval)[i] = COMPLEX(x)[i];
		if (xnames != R_NilValue)
		    SET_STRING_ELT(names, i, STRING_ELT(xnames, i));
	    }
	    else {
		COMPLEX(rval)[i].r = NA_REAL;
		COMPLEX(rval)[i].i = NA_REAL;
	    }
	break;
    case STRSXP:
	for (i = 0; i < len; i++)
	    if (i < lenx) {
		SET_STRING_ELT(rval, i, STRING_ELT(x, i));
		if (xnames != R_NilValue)
		    SET_STRING_ELT(names, i, STRING_ELT(xnames, i));
	    }
	    else
		SET_STRING_ELT(rval, i, NA_STRING);
	break;
    case LISTSXP:
	for (t = rval; t != R_NilValue; t = CDR(t), x = CDR(x)) {
	    SETCAR(t, CAR(x));
	    SET_TAG(t, TAG(x));
	}
    case VECSXP:
	for (i = 0; i < len; i++)
	    if (i < lenx) {
		SET_VECTOR_ELT(rval, i, VECTOR_ELT(x, i));
		if (xnames != R_NilValue)
		    SET_STRING_ELT(names, i, STRING_ELT(xnames, i));
	    }
	break;
    case RAWSXP:
	for (i = 0; i < len; i++)
	    if (i < lenx) {
		RAW(rval)[i] = RAW(x)[i];
		if (xnames != R_NilValue)
		    SET_STRING_ELT(names, i, STRING_ELT(xnames, i));
	    }
	    else
		RAW(rval)[i] = (Rbyte) 0;
	break;
    default:
	UNIMPLEMENTED_TYPE("length<-", x);
    }
    if (isVector(x) && xnames != R_NilValue)
	setAttrib(rval, R_NamesSymbol, names);
    UNPROTECT(1);
    return rval;
}


SEXP attribute_hidden do_lengthgets(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    R_len_t len;
    SEXP x, ans;

    checkArity(op, args);
    x = CAR(args);
    if( isObject(x) && DispatchOrEval(call, op, "length<-", args,
				      rho, &ans, 0, 1))
	return(ans);
    if (!isVector(x) && !isVectorizable(x))
       error(_("length<- invalid first argument"));
    if (length(CADR(args)) != 1)
       error(_("length<- invalid second argument"));
    len = asVecSize(CADR(args));
    if (len == NA_INTEGER)
       error(_("length<- missing value for 'length'"));
    return lengthgets(x, len);
}



/* For switch, evaluate the first arg, if it is a character then try */
/* to match the name with the remaining args, and evaluate the match, */
/* if there is no match then evaluate the first unnamed arg.  If the */
/* value of the first arg is not a character string then coerce it to */
/* an integer k and choose the kth argument from those that remain */
/* provided 0 < k < (nargs-1). For character matching, if the value */
/* is missing then take the next non-missing arg as the value. Then */
/* things like switch(as.character(answer), yes=, YES=1, no=, NO=2, 3) */
/* will work. */

static SEXP switchList(SEXP el, SEXP rho)
{
    SEXP h;
    if (CAR(el) == R_DotsSymbol) {
	h = findVar(CAR(el), rho);
	if (h == R_NilValue)
	    return R_NilValue;
	if (TYPEOF(h) != DOTSXP) {
	    if (h == R_MissingArg)
		return R_MissingArg;
	    error(_("... used in an incorrect context"));
	}
	return h;
    }
    else {
	error(_("invalid parameter in 'switch()'"));
	return R_NilValue;/* for -Wall */
    }
}

SEXP attribute_hidden do_switch(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    int argval;
    SEXP x, y, w;
    x = eval(CAR(args), rho);
    if (!isVector(x) || length(x) != 1)
	error(_("switch: EXPR must return a length 1 vector"));
    PROTECT(w = switchList(CDR(args), rho));
    if (isString(x)) {
	for (y = w; y != R_NilValue; y = CDR(y))
	    if (TAG(y) != R_NilValue && pmatch(STRING_ELT(x, 0), TAG(y), 1)) {
		while (CAR(y) == R_MissingArg && y != R_NilValue)
		    y = CDR(y);
		UNPROTECT(1);
		return (eval(CAR(y), rho));
	    }
	for (y = w; y != R_NilValue; y = CDR(y))
	    if (TAG(y) == R_NilValue) {
		UNPROTECT(1);
		return (eval(CAR(y), rho));
	    }
	UNPROTECT(1);
	return R_NilValue;
    }
    argval = asInteger(x);
    if (argval <= 0 || argval > (length(w))) {
	UNPROTECT(1);
	return R_NilValue;
    }
    x = eval(CAR(nthcdr(w, argval - 1)), rho);
    UNPROTECT(1);
    return x;
}