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/*
 *  R : A Computer Language for Statistical Data Analysis
 *  Copyright (C) 1995, 1996  Robert Gentleman and Ross Ihaka
 *  Copyright (C) 1998-2006   The R Development Core Team.
 *  Copyright (C) 2004        The R Foundation
 *
 *  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.
   Does rely on strcoll being correct.
 */

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

#include <Defn.h> /* => Utils.h with the protos from here */
#include <Rmath.h>

            /*--- Part I: Comparison Utilities ---*/

static int icmp(int x, int y, Rboolean nalast)
{
    if (x == NA_INTEGER && y == NA_INTEGER) return 0;
    if (x == NA_INTEGER)return nalast?1:-1;
    if (y == NA_INTEGER)return nalast?-1:1;
    if (x < y)      return -1;
    if (x > y)      return 1;
    return 0;
}

static int rcmp(double x, double y, Rboolean nalast)
{
    int nax = ISNAN(x), nay = ISNAN(y);
    if (nax && nay) return 0;
    if (nax)        return nalast?1:-1;
    if (nay)        return nalast?-1:1;
    if (x < y)      return -1;
    if (x > y)      return 1;
    return 0;
}

static int ccmp(Rcomplex x, Rcomplex y, Rboolean nalast)
{
    int nax = ISNAN(x.r), nay = ISNAN(y.r);
                /* compare real parts */
    if (nax && nay) return 0;
    if (nax)        return nalast?1:-1;
    if (nay)        return nalast?-1:1;
    if (x.r < y.r)  return -1;
    if (x.r > y.r)  return 1;
                /* compare complex parts */
    nax = ISNAN(x.i); nay = ISNAN(y.i);
    if (nax && nay) return 0;
    if (nax)        return nalast?1:-1;
    if (nay)        return nalast?-1:1;
    if (x.i < y.i)  return -1;
    if (x.i > y.i)  return 1;

    return 0;       /* equal */
}

static int scmp(SEXP x, SEXP y, Rboolean nalast)
{
    if (x == NA_STRING && y == NA_STRING) return 0;
    if (x == NA_STRING) return nalast?1:-1;
    if (y == NA_STRING) return nalast?-1:1;
    return STRCOLL(translateChar(x), translateChar(y));
}

Rboolean isUnsorted(SEXP x)
{
    int n, i;

    if (!isVectorAtomic(x))
    error(_("only atomic vectors can be tested to be sorted"));
    n = LENGTH(x);
    if(n >= 2)
    switch (TYPEOF(x)) {

        /* NOTE: x must have no NAs {is.na(.) in R};
           hence be faster than `rcmp()', `icmp()' for these two cases */

    case LGLSXP:
    case INTSXP:
        for(i = 0; i+1 < n ; i++)
        if(INTEGER(x)[i] > INTEGER(x)[i+1])
            return TRUE;
        break;
    case REALSXP:
        for(i = 0; i+1 < n ; i++)
        if(REAL(x)[i] > REAL(x)[i+1])
            return TRUE;
        break;
    case CPLXSXP:
        for(i = 0; i+1 < n ; i++)
        if(ccmp(COMPLEX(x)[i], COMPLEX(x)[i+1], TRUE) > 0)
            return TRUE;
        break;
    case STRSXP:
        for(i = 0; i+1 < n ; i++)
        if(scmp(STRING_ELT(x, i ),
            STRING_ELT(x,i+1), TRUE) > 0)
            return TRUE;
        break;
    default:
        UNIMPLEMENTED_TYPE("isUnsorted", x);
    }
    return FALSE;/* sorted */
}

SEXP attribute_hidden do_isunsorted(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    checkArity(op, args);
    return ScalarLogical(isUnsorted(CAR(args)));
}


            /*--- Part II: Complete (non-partial) Sorting ---*/


/* SHELLsort -- corrected from R. Sedgewick `Algorithms in C'
 *      (version of BDR's lqs():*/
#define sort_body                   \
    Rboolean nalast=TRUE;               \
    int i, j, h;                    \
                            \
    for (h = 1; h <= n / 9; h = 3 * h + 1);     \
    for (; h > 0; h /= 3)               \
    for (i = h; i < n; i++) {           \
        v = x[i];                   \
        j = i;                  \
        while (j >= h && TYPE_CMP(x[j - h], v, nalast) > 0) \
         { x[j] = x[j - h]; j -= h; }       \
        x[j] = v;                   \
    }

void R_isort(int *x, int n)
{
    int v;
#define TYPE_CMP icmp
    sort_body
#undef TYPE_CMP
}

void R_rsort(double *x, int n)
{
    double v;
#define TYPE_CMP rcmp
    sort_body
#undef TYPE_CMP
}

void R_csort(Rcomplex *x, int n)
{
    Rcomplex v;
#define TYPE_CMP ccmp
    sort_body
#undef TYPE_CMP
}


/* used in platform.c */
void attribute_hidden ssort(SEXP *x, int n)
{
    SEXP v;
#define TYPE_CMP scmp
    sort_body
#undef TYPE_CMP
}

void rsort_with_index(double *x, int *indx, int n)
{
    double v;
    int i, j, h, iv;

    for (h = 1; h <= n / 9; h = 3 * h + 1);
    for (; h > 0; h /= 3)
    for (i = h; i < n; i++) {
        v = x[i]; iv = indx[i];
        j = i;
        while (j >= h && rcmp(x[j - h], v, TRUE) > 0)
         { x[j] = x[j - h]; indx[j] = indx[j-h]; j -= h; }
        x[j] = v; indx[j] = iv;
    }
}

void revsort(double *a, int *ib, int n)
{
/* Sort a[] into descending order by "heapsort";
 * sort ib[] alongside;
 * if initially, ib[] = 1...n, it will contain the permutation finally
 */

    int l, j, ir, i;
    double ra;
    int ii;

    if (n <= 1) return;

    a--; ib--;

    l = (n >> 1) + 1;
    ir = n;

    for (;;) {
    if (l > 1) {
        l = l - 1;
        ra = a[l];
        ii = ib[l];
    }
    else {
        ra = a[ir];
        ii = ib[ir];
        a[ir] = a[1];
        ib[ir] = ib[1];
        if (--ir == 1) {
        a[1] = ra;
        ib[1] = ii;
        return;
        }
    }
    i = l;
    j = l << 1;
    while (j <= ir) {
        if (j < ir && a[j] > a[j + 1]) ++j;
        if (ra > a[j]) {
        a[i] = a[j];
        ib[i] = ib[j];
        j += (i = j);
        }
        else
        j = ir + 1;
    }
    a[i] = ra;
    ib[i] = ii;
    }
}


SEXP attribute_hidden do_sort(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP ans;
    Rboolean decreasing;

    checkArity(op, args);

    decreasing = asLogical(CADR(args));
    if(decreasing == NA_LOGICAL)
    error(_("'decreasing' must be TRUE or FALSE"));
    if(CAR(args) == R_NilValue) return R_NilValue;
    if(!isVectorAtomic(CAR(args)))
    error(_("only atomic vectors can be sorted"));
    if(TYPEOF(CAR(args)) == RAWSXP)
    error(_("raw vectors cannot be sorted"));
    /* we need consistent behaviour here, including dropping attibutes,
       so as from 2.3.0 we always duplicate. */
    ans = duplicate(CAR(args));
    SET_ATTRIB(ans, R_NilValue);  /* this is never called with names */
    sortVector(ans, decreasing);
    return(ans);
}

/* faster versions of shellsort, following Sedgewick (1986) */

static const int incs[16] = {1073790977, 268460033, 67121153, 16783361, 4197377,
               1050113, 262913, 65921, 16577, 4193, 1073, 281, 77,
               23, 8, 1};

#define sort2_body \
    for (h = incs[t]; t < 16; h = incs[++t]) \
    for (i = h; i < n; i++) { \
        v = x[i]; \
        j = i; \
        while (j >= h && x[j - h] less v) { x[j] = x[j - h]; j -= h; } \
        x[j] = v; \
    }


static void R_isort2(int *x, int n, Rboolean decreasing)
{
    int v;
    int i, j, h, t;

    for (t = 0; incs[t] > n; t++);
    if(decreasing)
#define less <
    sort2_body
#undef less
    else
#define less >
    sort2_body
#undef less
}

static void R_rsort2(double *x, int n, Rboolean decreasing)
{
    double v;
    int i, j, h, t;

    for (t = 0; incs[t] > n; t++);
    if(decreasing)
#define less <
    sort2_body
#undef less
    else
#define less >
    sort2_body
#undef less
}

static void R_csort2(Rcomplex *x, int n, Rboolean decreasing)
{
    Rcomplex v;
    int i, j, h, t;

    for (t = 0; incs[t] > n; t++);
    for (h = incs[t]; t < 16; h = incs[++t])
    for (i = h; i < n; i++) {
        v = x[i];
        j = i;
        if(decreasing)
        while (j >= h && (x[j - h].r < v.r ||
                  (x[j - h].r == v.r && x[j - h].i < v.i)))
        { x[j] = x[j - h]; j -= h; }
        else
        while (j >= h && (x[j - h].r > v.r ||
                  (x[j - h].r == v.r && x[j - h].i > v.i)))
        { x[j] = x[j - h]; j -= h; }
        x[j] = v;
    }
}

static void ssort2(SEXP *x, int n, Rboolean decreasing)
{
    SEXP v;
    int i, j, h, t;

    for (t = 0; incs[t] > n; t++);
    for (h = incs[t]; t < 16; h = incs[++t])
    for (i = h; i < n; i++) {
        v = x[i];
        j = i;
        if(decreasing)
        while (j >= h && scmp(x[j - h], v, TRUE) < 0)
        { x[j] = x[j - h]; j -= h; }
        else
        while (j >= h && scmp(x[j - h], v, TRUE) > 0)
        { x[j] = x[j - h]; j -= h; }
        x[j] = v;
    }
}

void sortVector(SEXP s, Rboolean decreasing)
{
    int n = LENGTH(s);
    if (n >= 2 && (decreasing || isUnsorted(s)))
    switch (TYPEOF(s)) {
    case LGLSXP:
    case INTSXP:
        R_isort2(INTEGER(s), n, decreasing);
        break;
    case REALSXP:
        R_rsort2(REAL(s), n, decreasing);
        break;
    case CPLXSXP:
        R_csort2(COMPLEX(s), n, decreasing);
        break;
    case STRSXP:
        ssort2(STRING_PTR(s), n, decreasing);
        break;
    default:
        UNIMPLEMENTED_TYPE("sortVector", s);
    }
}


            /*--- Part III: Partial Sorting ---*/

/*
   Partial sort so that x[k] is in the correct place, smaller to left,
   larger to right

   NOTA BENE:  k < n  required, and *not* checked here but in do_psort();
           -----  infinite loop possible otherwise!
 */
#define psort_body                      \
    Rboolean nalast=TRUE;                   \
    int L, R, i, j;                     \
                                \
    for (L = lo, R = hi; L < R; ) {             \
    v = x[k];                       \
    for(i = L, j = R; i <= j;) {                \
        while (TYPE_CMP(x[i], v, nalast) < 0) i++;          \
        while (TYPE_CMP(v, x[j], nalast) < 0) j--;          \
        if (i <= j) { w = x[i]; x[i++] = x[j]; x[j--] = w; }\
    }                           \
    if (j < k) L = i;                   \
    if (k < i) R = j;                   \
    }


static void iPsort2(int *x, int lo, int hi, int k)
{
    int v, w;
#define TYPE_CMP icmp
    psort_body
#undef TYPE_CMP
}

static void rPsort2(double *x, int lo, int hi, int k)
{
    double v, w;
#define TYPE_CMP rcmp
    psort_body
#undef TYPE_CMP
}

static void cPsort2(Rcomplex *x, int lo, int hi, int k)
{
    Rcomplex v, w;
#define TYPE_CMP ccmp
    psort_body
#undef TYPE_CMP
}


static void sPsort2(SEXP *x, int lo, int hi, int k)
{
    SEXP v, w;
#define TYPE_CMP scmp
    psort_body
#undef TYPE_CMP
}

/* elements of ind are 1-based, lo and hi are 0-based */

static void Psort(SEXP x, int lo, int hi, int k)
{
    /* Rprintf("looking for index %d in (%d, %d)\n", k, lo, hi);*/
    switch (TYPEOF(x)) {
    case LGLSXP:
    case INTSXP:
    iPsort2(INTEGER(x), lo, hi, k);
    break;
    case REALSXP:
    rPsort2(REAL(x), lo, hi, k);
    break;
    case CPLXSXP:
    cPsort2(COMPLEX(x), lo, hi, k);
    break;
    case STRSXP:
    sPsort2(STRING_PTR(x), lo, hi, k);
    break;
    default:
    UNIMPLEMENTED_TYPE("Psort", x);
    }
}

static void Psort0(SEXP x, int lo, int hi, int *ind, int k)
{
    if(k < 1 || hi-lo < 1) return;
    if(k <= 1) 
    Psort(x, lo, hi, ind[0]-1);
    else {
    /* Look for index nearest the centre of the range */
    int i, This = 0, mid = (lo+hi)/2, z;
    for(i = 0; i < k; i++)
        if(ind[i]-1 <= mid) This = i;
    z = ind[This]-1;
    Psort(x, lo, hi, z);
    Psort0(x, lo, z-1, ind, This);
    Psort0(x, z+1, hi, ind + This + 1, k - This -1);
    }
}

/* Needed for mistaken decision to put these in the API */
void iPsort(int *x, int n, int k)
{
    iPsort2(x, 0, n-1, k);
}

void rPsort(double *x, int n, int k)
{
    rPsort2(x, 0, n-1, k);
}

void cPsort(Rcomplex *x, int n, int k)
{
    cPsort2(x, 0, n-1, k);
}



/* FUNCTION psort(x, indices) */
SEXP attribute_hidden do_psort(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    int i, k, n;
    int *l;
    checkArity(op, args);

    if (!isVectorAtomic(CAR(args)))
    error(_("only atomic vectors can be sorted"));
    if(TYPEOF(CAR(args)) == RAWSXP)
    error(_("raw vectors cannot be sorted"));
    n = LENGTH(CAR(args));
    SETCADR(args, coerceVector(CADR(args), INTSXP));
    l = INTEGER(CADR(args));
    k = LENGTH(CADR(args));
    for (i = 0; i < k; i++) {
    if (l[i] == NA_INTEGER)
        error(_("NA index"));
    if (l[i] < 1 || l[i] > n)
        error(_("index %d outside bounds"), l[i]);
    }
    SETCAR(args, duplicate(CAR(args)));
    SET_ATTRIB(CAR(args), R_NilValue);  /* remove all attributes */
    Psort0(CAR(args), 0, n - 1, l, k);
    return CAR(args);
}


            /*--- Part IV : Rank & Order ---*/

static int equal(int i, int j, SEXP x, Rboolean nalast)
{
    int c=-1;

    switch (TYPEOF(x)) {
    case LGLSXP:
    case INTSXP:
    c = icmp(INTEGER(x)[i], INTEGER(x)[j], nalast);
    break;
    case REALSXP:
    c = rcmp(REAL(x)[i], REAL(x)[j], nalast);
    break;
    case CPLXSXP:
    c = ccmp(COMPLEX(x)[i], COMPLEX(x)[j], nalast);
    break;
    case STRSXP:
    c = scmp(STRING_ELT(x, i), STRING_ELT(x, j), nalast);
    break;
    default:
    UNIMPLEMENTED_TYPE("equal", x);
    break;
    }
    if (c == 0)
    return 1;
    return 0;
}

static int greater(int i, int j, SEXP x, Rboolean nalast, Rboolean decreasing)
{
    int c = -1;

    switch (TYPEOF(x)) {
    case LGLSXP:
    case INTSXP:
    c = icmp(INTEGER(x)[i], INTEGER(x)[j], nalast);
    break;
    case REALSXP:
    c = rcmp(REAL(x)[i], REAL(x)[j], nalast);
    break;
    case CPLXSXP:
    c = ccmp(COMPLEX(x)[i], COMPLEX(x)[j], nalast);
    break;
    case STRSXP:
    c = scmp(STRING_ELT(x, i), STRING_ELT(x, j), nalast);
    break;
    default:
    UNIMPLEMENTED_TYPE("greater", x);
    break;
    }
    if (decreasing) c = -c;
    if (c > 0 || (c == 0 && j < i)) return 1; else return 0;
}

/* listgreater(): used as greater_sub in orderVector() in do_order(...) */
static int listgreater(int i, int j, SEXP key, Rboolean nalast,
               Rboolean decreasing)
{
    SEXP x;
    int c = -1;

    while (key != R_NilValue) {
    x = CAR(key);
    switch (TYPEOF(x)) {
    case LGLSXP:
    case INTSXP:
        c = icmp(INTEGER(x)[i], INTEGER(x)[j], nalast);
        break;
    case REALSXP:
        c = rcmp(REAL(x)[i], REAL(x)[j], nalast);
        break;
    case CPLXSXP:
        c = ccmp(COMPLEX(x)[i], COMPLEX(x)[j], nalast);
        break;
    case STRSXP:
        c = scmp(STRING_ELT(x, i), STRING_ELT(x, j), nalast);
        break;
    default:
        UNIMPLEMENTED_TYPE("listgreater", x);
    }
    if (decreasing) c = -c;
    if (c > 0)
        return 1;
    if (c < 0)
        return 0;
    key = CDR(key);
    }
    if (c == 0 && i < j) return 0; else return 1;
}

/* Needs indx set to 1...n initially */
static void orderVector(int *indx, int n, SEXP key, Rboolean nalast,
            Rboolean decreasing, int greater_sub(int, int, SEXP, Rboolean, Rboolean))
{
    int i, j, h, t;
    int itmp;

    for (t = 0; incs[t] > n; t++);
    for (h = incs[t]; t < 16; h = incs[++t])
    for (i = h; i < n; i++) {
        itmp = indx[i];
        j = i;
        while (j >= h &&
           greater_sub(indx[j - h], itmp, key, nalast^decreasing,
                   decreasing)) {
        indx[j] = indx[j - h];
        j -= h;
        }
        indx[j] = itmp;
    }
}

#define sort2_with_index \
            for (h = incs[t]; t < 16; h = incs[++t]) \
        for (i = lo + h; i <= hi; i++) { \
            itmp = indx[i]; \
            j = i; \
            while (j >= lo + h && less(indx[j - h], itmp)) { \
            indx[j] = indx[j - h]; j -= h; } \
            indx[j] = itmp; \
        }


/* Needs indx set to 1...n initially.
   Also used by do_options.
 */
void attribute_hidden
orderVector1(int *indx, int n, SEXP key, Rboolean nalast, Rboolean decreasing)
{
    int c, i, j, h, t, lo = 0, hi = n-1;
    int itmp, *isna, numna = 0;
    int *ix = NULL /* -Wall */;
    double *x = NULL /* -Wall */;
    Rcomplex *cx = NULL /* -Wall */;
    SEXP *sx = NULL /* -Wall */;
    
    switch (TYPEOF(key)) {
    case LGLSXP:
    case INTSXP:
    ix = INTEGER(key);
    break;
    case REALSXP:
    x = REAL(key);
    break;
    case STRSXP:
    sx = STRING_PTR(key);
    break;
    case CPLXSXP:
    cx = COMPLEX(key);
    break;
    }

    /* First sort NAs to one end */
    isna = (int *) malloc(n * sizeof(int));
    switch (TYPEOF(key)) {
    case LGLSXP:
    case INTSXP:
    for (i = 0; i < n; i++) isna[i] = (ix[i] == NA_INTEGER);
    break;
    case REALSXP:
    for (i = 0; i < n; i++) isna[i] = ISNAN(x[i]);
    break;
    case STRSXP:
    for (i = 0; i < n; i++) isna[i] = (sx[i] == NA_STRING);
    break;
    case CPLXSXP:
    for (i = 0; i < n; i++) isna[i] = ISNAN(cx[i].r) || ISNAN(cx[i].i);
    break;
    default:
    UNIMPLEMENTED_TYPE("orderVector1", key);
    }
    for (i = 0; i < n; i++) numna += isna[i];

    if(numna)
    switch (TYPEOF(key)) {
    case LGLSXP:
    case INTSXP:
    case REALSXP:
    case STRSXP:
    case CPLXSXP:
        if (!nalast) for (i = 0; i < n; i++) isna[i] = !isna[i];
        for (t = 0; incs[t] > n; t++);
#define less(a, b) (isna[a] > isna[b] || (isna[a] == isna[b] && a > b))
        sort2_with_index
#undef less
        if(nalast) hi -= numna; else lo += numna;
    }

    /* Shell sort isn't stable, so add test on index */
    for (t = 0; incs[t] > hi-lo+1; t++);
    switch (TYPEOF(key)) {
    case LGLSXP:
    case INTSXP:
    if (decreasing) {
#define less(a, b) (ix[a] < ix[b] || (ix[a] == ix[b] && a > b))
        sort2_with_index
#undef less
        } else {
#define less(a, b) (ix[a] > ix[b] || (ix[a] == ix[b] && a > b))
        sort2_with_index
#undef less
        }
    break;
    case REALSXP:
    if (decreasing) {
#define less(a, b) (x[a] < x[b] || (x[a] == x[b] && a > b))
        sort2_with_index
#undef less
        } else {
#define less(a, b) (x[a] > x[b] || (x[a] == x[b] && a > b))
        sort2_with_index
#undef less
        }
    break;
    case CPLXSXP:
    if (decreasing) {
#define less(a, b) (ccmp(cx[a], cx[b], 0) < 0 || (cx[a].r == cx[b].r && cx[a].i == cx[b].i && a > b))
        sort2_with_index
#undef less
        } else {
#define less(a, b) (ccmp(cx[a], cx[b], 0) > 0 || (cx[a].r == cx[b].r && cx[a].i == cx[b].i && a > b))
        sort2_with_index
#undef less
        }
    break;
    case STRSXP:
    if (decreasing)
#define less(a, b) (c=STRCOLL(translateChar(sx[a]),translateChar(sx[b])), c < 0 || (c == 0 && a > b))
        sort2_with_index
#undef less
        else
#define less(a, b) (c=STRCOLL(translateChar(sx[a]),translateChar(sx[b])), c > 0 || (c == 0 && a > b))
        sort2_with_index
#undef less
    break;
    default:
#define less(a, b) greater(a, b, key, nalast^decreasing, decreasing)
    sort2_with_index
#undef less
    }
    free(isna);
}

/* FUNCTION order(...) */
SEXP attribute_hidden do_order(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP ap, ans;
    int i, n = -1, narg = 0;
    Rboolean nalast, decreasing;

    nalast = asLogical(CAR(args));
    if(nalast == NA_LOGICAL)
    error(_("invalid '%s' value"), "na.last");
    args = CDR(args);
    decreasing = asLogical(CAR(args));
    if(decreasing == NA_LOGICAL)
    error(_("'decreasing' must be TRUE or FALSE"));
    args = CDR(args);
    if (args == R_NilValue)
    return R_NilValue;

    if (isVector(CAR(args)))
    n = LENGTH(CAR(args));
    for (ap = args; ap != R_NilValue; ap = CDR(ap), narg++) {
    if (!isVector(CAR(ap)))
        error(_("argument %d is not a vector"), narg + 1);
    if (LENGTH(CAR(ap)) != n)
        error(_("argument lengths differ"));
    }
    ans = allocVector(INTSXP, n);
    if (n != 0) {
    for (i = 0; i < n; i++) INTEGER(ans)[i] = i;
    if(narg == 1)
        orderVector1(INTEGER(ans), n, CAR(args), nalast, decreasing);
    else
        orderVector(INTEGER(ans), n, args, nalast, decreasing, listgreater);
    for (i = 0; i < n; i++) INTEGER(ans)[i]++;
    }
    return ans;
}

/* FUNCTION: rank(x) */
SEXP attribute_hidden do_rank(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP rank, indx, x;
    int *in;
    double *rk;
    int i, j, k, n;
    const char *ties_str;
    enum {AVERAGE, MAX, MIN} ties_kind = AVERAGE;

    checkArity(op, args);
    if (args == R_NilValue)
    return R_NilValue;
    x = CAR(args);
    if (!isVectorAtomic(x))
    error(_("argument is not an atomic vector"));
    if(TYPEOF(x) == RAWSXP)
    error(_("raw vectors cannot be sorted"));
    n = LENGTH(x);
    PROTECT(indx = allocVector(INTSXP, n));
    PROTECT(rank = allocVector(REALSXP, n));
    UNPROTECT(2);
    ties_str = CHAR(asChar(CADR(args)));
    if(!strcmp(ties_str, "average"))    ties_kind = AVERAGE;
    else if(!strcmp(ties_str, "max"))   ties_kind = MAX;
    else if(!strcmp(ties_str, "min"))   ties_kind = MIN;
    else error(_("invalid ties.method for rank() [should never happen]"));
    if (n > 0) {
    in = INTEGER(indx);
    rk = REAL(rank);
    for (i = 0; i < n; i++)
        in[i] = i;
    orderVector1(in, n, x, TRUE, FALSE);
    i = 0;
    while (i < n) {
        j = i;
        while ((j < n - 1) && equal(in[j], in[j + 1], x, TRUE))
        j++;
        if (i != j) { /* ties */
        switch(ties_kind) {
            case AVERAGE:
            for (k = i; k <= j; k++)
                rk[in[k]] = (i + j + 2) / 2.; break;
            case MAX:
            for (k = i; k <= j; k++) rk[in[k]] = j+1; break;
            case MIN:
            for (k = i; k <= j; k++) rk[in[k]] = i+1; break;
        }
        }
        else
        rk[in[i]] = i + 1;
        i = j + 1;
    }
    }
    return rank;
}

#include <R_ext/RS.h>

SEXP attribute_hidden do_radixsort(SEXP call, SEXP op, SEXP args, SEXP rho)
{
    SEXP x, ans;
    Rboolean nalast, decreasing;
    unsigned int *cnts;
    int i, n, tmp, xmax = NA_INTEGER, xmin = NA_INTEGER, off, napos;

    checkArity(op, args);

    x = CAR(args);
    nalast = asLogical(CADR(args));
    if(nalast == NA_LOGICAL)
    error(_("invalid '%s' value"), "na.last");
    decreasing = asLogical(CADDR(args));
    if(decreasing == NA_LOGICAL)
    error(_("'decreasing' must be TRUE or FALSE"));
    off = nalast^decreasing ? 0 : 1;
    n = LENGTH(x);
    PROTECT(ans = allocVector(INTSXP, n));
    for(i = 0; i < n; i++) {
    tmp = INTEGER(x)[i];
    if(tmp == NA_INTEGER) continue;
    if(tmp < 0) error(_("negative value in 'x'"));
    if(xmax == NA_INTEGER || tmp > xmax) xmax = tmp;
    if(xmin == NA_INTEGER || tmp < xmin) xmin = tmp;
    }
    if(xmin == NA_INTEGER) {  /* all NAs, so nothing to do */
    for(i = 0; i < n; i++) INTEGER(ans)[i] = i+1;
    UNPROTECT(1);
    return ans;
    }

    xmax -= xmin;
    if(xmax > 100000) error(_("too large a range of values in 'x'"));
    napos = off ? 0 : xmax + 1;
    off -= xmin;
    /* alloca is fine here: we know this is small */
    cnts = (unsigned int *) alloca((xmax+1)*sizeof(unsigned int));
    R_CheckStack();

    for(i = 0; i <= xmax+1; i++) cnts[i] = 0;
    for(i = 0; i < n; i++) {
    if(INTEGER(x)[i] == NA_INTEGER) cnts[napos]++;
    else cnts[off+INTEGER(x)[i]]++;
    }

    for(i = 1; i <= xmax+1; i++) cnts[i] += cnts[i-1];
    if(decreasing)
    for(i = 0; i < n; i++){
        tmp = INTEGER(x)[i];
        INTEGER(ans)[n-(cnts[(tmp==NA_INTEGER) ? napos : off+tmp]--)] = i+1;
    }
    else
    for(i = n-1; i >= 0; i--) {
        tmp = INTEGER(x)[i];
        INTEGER(ans)[--cnts[(tmp==NA_INTEGER) ? napos : off+tmp]] = i+1;
    }

    UNPROTECT(1);
    return ans;
}