/**************************************************************************/
/*                                                                        */
/*                                 Sources                                */
/*                                from  the                               */
/*                           XSC SOFTWARE PACKAGE                         */
/*                                                                        */
/*                Copyright (c) 1997 University of Karlsruhe              */
/*                     Institute for Appl. Mathematics                    */
/*                                                                        */
/* This program is free software for non-commercial use. For details, see */
/* the file LICENSE.XSC, distributed with this software package.          */
/*                                                                        */
/* This program is distributed WITHOUT ANY WARRANTY. For details, see the */
/* file LICENSE.XSC, distributed with this software package.              */
/*                                                                        */
/**************************************************************************/

/* RCS $Id: t_itan.c,v 1.2 1997/09/25 18:18:59 ae59 Exp $ */
/*
$Log: t_itan.c,v $
 * Revision 1.2  1997/09/25  18:18:59  ae59
 * Copyright-message
 *
 * Revision 1.1  1994/01/27  13:25:37  ae59
 * Put under RCS control
 *
 */
/****************************************************************/
/*      Date            : 1991-11-14                            */
/*      1991-11-14 : save and restore flags                     */
/*      1991-09-24 : macro call StdFctInterval replaced         */
/*      1991-09-17 : remove semicolon after makro               */
/*      1991-09-06 : reduce maximum line length                 */
/****************************************************************/

#ifdef AIX
#include "/u/p88c/runtime/tbyte/t_defs.h"
#else
#include "t_defs.h"
#endif

/* StdFctInterval(t_itan,itanee) */
#ifdef LINT_ARGS
a_intv t_itan(a_intv ai)
#else
a_intv t_itan(ai)

a_intv ai;
#endif
        {

        a_intv   res;
        int      rnd, rc;
        IExtReal  a, r;

        E_SPUSH("t_itan")

        rnd = getrndmode();
        longreal_to_extreal((LongReal *)&ai.INF, &a.l);
        longreal_to_extreal((LongReal *)&ai.SUP, &a.u);

        if ((rc = itanee(&a, &r))!=0)
            ieee_aborti1(rc, &ai);

        setrndmode(DOWN);
        if ((rc = extreal_to_longreal(&r.l, (LongReal *)&res.INF))!=0)
             ieee_aborti1(rc, &ai);
        setrndmode(UP);
        if ((rc = extreal_to_longreal(&r.u, (LongReal *)&res.SUP))!=0)
            ieee_aborti1(rc, &ai);
        setrndmode(rnd);

        E_SPOPP("t_itan")
        return res;
        }

/* ------------------------------------------------------------ */

/*--------------------------------------------------------------*
 | tanee                                                        |
 *--------------------------------------------------------------*/
#ifdef ANSI_C
#ifdef LINT_ARGS
int itanee (const IExtReal *arg, IExtReal *res)
#else
int itanee (arg, res)
const IExtReal   *arg;
      IExtReal   *res;
#endif /* LINT_ARGS */
#else  /* NOT ANSI_C */
#ifdef LINT_ARGS
int itanee (IExtReal *arg, IExtReal *res)
#else
int itanee (arg, res)
IExtReal   *arg;
IExtReal   *res;
#endif /* LINT_ARGS */
#endif /* ANSI_C */
{
   DReal       vu;    /* Produkt des Arguments mit 2/pi  upper Bound */
   DReal       vl;    /* Produkt des Arguments mit 2/pi  lower Bound */
   ExtReal     ju;    /* Ganzzahliger Anteil von v       upper Bound */
   ExtReal     jl;    /* Ganzzahliger Anteil von v       lower Bound */
   ExtReal     tu;    /* reduziertes Argument upper Bound            */
   ExtReal     tl;    /* reduziertes Argument lower Bound            */
   ExtReal     jd;    /* Differenz j.u - j.l, max(jdiff):=4          */
   int         jdiff; /* =jd                                         */
   int         jmod4u;/* j.u modulo 4                                */
   int         jmod4l;/* j.l modulo 4                                */
   int         retru; /* Rueckgabe Reduktion                         */
   int         retrl; /* Rueckgabe Reduktion                         */
   int         retu;  /* Rueckgabe tancot                            */
   int         retl;  /* Rueckgabe tancot                            */
   int         ret;   /* Rueckgabe                                   */
   int         check; /* Rueckgabe von Makro ArgCheck                */

   /* --- pruefe Argument, dann Pruefung aus --- */
   ArgCheckI1(ITan, arg, res);
   arg_check = Off;

   /* --- ganzzahliger Anteil von arg --- */
   gza_trg(&(arg->u), J_Init_Tan, Period_PiQuart, &vu, &ju, &jmod4u);
   gza_trg(&(arg->l), J_Init_Tan, Period_PiQuart, &vl, &jl, &jmod4l);

   /* --- jdiff --- */
   subee(&ju, &jl, &jd);
   if (1 == cmpee(&jd, &Four)) copyee(&Four, &jd);
   extreal_to_int(&jd, &jdiff);

   /* --- ArgumentPruefung auf Pol, Abbruch --- */
   if ((jdiff == 4) || (jmod4l <= 1 && jmod4u >= 2)) {
      ret = exc_handle_i1(ITan, ExcISing, arg, res);
      arg_check = On;
      return ret;
   }

   /* --- Reduktion  --- */
   retru = red_trg(&vu, &ju, jmod4u, &tu);
   retrl = red_trg(&vl, &jl, jmod4l, &tl);

   /* --- tan(t*pi/4) --- */
   retu = tancot(&tu, jmod4u, &(res->u));
   retl = tancot(&tl, jmod4l, &(res->l));

   /* --- Abbruch bei Fehler --- */
   if(NoErr!=retu||NoErr!=retl) {
      arg_check = On;
      return max(retu, retl);
   }

   /* --- Rundungs-Fehler --- */
   iround_rel(res, &EpsTan, res);

   /* Ergebnisverbesserung in Spezialfaellen */
#if INT_HPREC
   { int vz;
     vz = SGNE(&(arg->l));
     if (vz==POS&&1==cmpee(&(arg->l), &(res->l))
         &&-1==cmpee(&(arg->l), &IPiHalf.l))    /* tan x >= x */
        copyee(&(arg->l), &(res->l));
     vz = SGNE(&(arg->u));
     if (vz==NEG&&-1==cmpee(&(arg->u), &(res->u))
         &&-1==cmpabsee(&(arg->u), &IPiHalf.l))   /* tan x <= x */
        copyee(&(arg->u), &(res->u));
   }
#endif /* INT_HPREC */

   /* --- ArgPruefung wieder an --- */
   arg_check = On;

   /* --- kein Fehler mehr moeglich, nur PLOSS von red_trg --- */
   return max(retru, retrl);
} /* itanee() */


