slatec-bessel-cpp/f2c/zuchk.cpp

/* zuchk.f -- translated by f2c (version 20100827).
   This file no longer depends on f2c.
*/

#include "slatec-internal.hpp"

int zuchk_(double *yr, double *yi, integer *nz,
	double *ascle, double *tol)
{
    double wi, ss, st, wr;

/* ***BEGIN PROLOGUE  ZUCHK */
/* ***SUBSIDIARY */
/* ***PURPOSE  Subsidiary to SERI, ZUOIK, ZUNK1, ZUNK2, ZUNI1, ZUNI2 and */
/*            ZKSCL */
/* ***LIBRARY   SLATEC */
/* ***TYPE      ALL (CUCHK-A, ZUCHK-A) */
/* ***AUTHOR  Amos, D. E., (SNL) */
/* ***DESCRIPTION */

/*      Y ENTERS AS A SCALED QUANTITY WHOSE MAGNITUDE IS GREATER THAN */
/*      EXP(-ALIM)=ASCLE=1.0E+3*D1MACH(1)/TOL. THE TEST IS MADE TO SEE */
/*      IF THE MAGNITUDE OF THE REAL OR IMAGINARY PART WOULD UNDERFLOW */
/*      WHEN Y IS SCALED (BY TOL) TO ITS PROPER VALUE. Y IS ACCEPTED */
/*      IF THE UNDERFLOW IS AT LEAST ONE PRECISION BELOW THE MAGNITUDE */
/*      OF THE LARGEST COMPONENT; OTHERWISE THE PHASE ANGLE DOES NOT HAVE */
/*      ABSOLUTE ACCURACY AND AN UNDERFLOW IS ASSUMED. */

/* ***SEE ALSO  SERI, ZKSCL, ZUNI1, ZUNI2, ZUNK1, ZUNK2, ZUOIK */
/* ***ROUTINES CALLED  (NONE) */
/* ***REVISION HISTORY  (YYMMDD) */
/*   ??????  DATE WRITTEN */
/*   910415  Prologue converted to Version 4.0 format.  (BAB) */
/* ***END PROLOGUE  ZUCHK */

/*     COMPLEX Y */
/* ***FIRST EXECUTABLE STATEMENT  ZUCHK */
    *nz = 0;
    wr = abs(*yr);
    wi = abs(*yi);
    st = min(wr,wi);
    if (st > *ascle) {
	return 0;
    }
    ss = max(wr,wi);
    st /= *tol;
    if (ss < st) {
	*nz = 1;
    }
    return 0;
} /* zuchk_ */