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SUBROUTINE MC01SY( M, E, B, A, OVFLOW )
C
C SLICOT RELEASE 5.0.
C
C Copyright (c) 2002-2009 NICONET e.V.
C
C This program is free software: you can redistribute it and/or
C modify it under the terms of the GNU General Public License as
C published by the Free Software Foundation, either version 2 of
C the License, or (at your option) any later version.
C
C This program is distributed in the hope that it will be useful,
C but WITHOUT ANY WARRANTY; without even the implied warranty of
C MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
C GNU General Public License for more details.
C
C You should have received a copy of the GNU General Public License
C along with this program. If not, see
C <http://www.gnu.org/licenses/>.
C
C PURPOSE
C
C To find a real number A from its mantissa M and its exponent E,
C i.e.,
C A = M * B**E.
C M and E need not be the standard floating-point values.
C If ABS(A) < B**(EMIN-1), i.e. the smallest positive model number,
C then the routine returns A = 0.
C If M = 0, then the routine returns A = 0 regardless of the value
C of E.
C
C ARGUMENTS
C
C Input/Output Parameters
C
C M (input) DOUBLE PRECISION
C The mantissa of the floating-point representation of A.
C
C E (input) INTEGER
C The exponent of the floating-point representation of A.
C
C B (input) INTEGER
C The base of the floating-point arithmetic.
C
C A (output) DOUBLE PRECISION
C The value of M * B**E.
C
C OVFLOW (output) LOGICAL
C The value .TRUE., if ABS(M) * B**E >= B**EMAX (where EMAX
C is the largest possible exponent) and .FALSE. otherwise.
C A is not defined if OVFLOW = .TRUE..
C
C NUMERICAL ASPECTS
C
C None.
C
C CONTRIBUTOR
C
C Release 3.0: V. Sima, Katholieke Univ. Leuven, Belgium, Mar. 1997.
C Supersedes Release 2.0 routine MC01GY by A.J. Geurts.
C
C REVISIONS
C
C -
C
C ******************************************************************
C
C .. Parameters ..
DOUBLE PRECISION ZERO, ONE
PARAMETER ( ZERO = 0.0D0, ONE = 1.0D0 )
C .. Scalar Arguments ..
LOGICAL OVFLOW
INTEGER B, E
DOUBLE PRECISION A, M
C .. Local Scalars ..
INTEGER EMAX, EMIN, ET, EXPON
DOUBLE PRECISION BASE, MT
C .. External Functions ..
DOUBLE PRECISION DLAMCH
EXTERNAL DLAMCH
C .. Intrinsic Functions ..
INTRINSIC ABS, MOD
C .. Executable Statements ..
C
OVFLOW = .FALSE.
C
IF ( ( M.EQ.ZERO ) .OR. ( E.EQ.0 ) ) THEN
A = M
RETURN
END IF
C
C Determination of the mantissa MT and the exponent ET of the
C standard floating-point representation.
C
EMIN = DLAMCH( 'Minimum exponent' )
EMAX = DLAMCH( 'Largest exponent' )
MT = M
ET = E
C WHILE ( ABS( MT ) >= B ) DO
20 IF ( ABS( MT ).GE.B ) THEN
MT = MT/B
ET = ET + 1
GO TO 20
END IF
C END WHILE 20
C WHILE ( ABS( MT ) < 1 ) DO
40 IF ( ABS( MT ).LT.ONE ) THEN
MT = MT*B
ET = ET - 1
GO TO 40
END IF
C END WHILE 40
C
IF ( ET.LT.EMIN ) THEN
A = ZERO
RETURN
END IF
C
IF ( ET.GE.EMAX ) THEN
OVFLOW = .TRUE.
RETURN
END IF
C
C Computation of the value of A by the relation
C M * B**E = A * (BASE)**EXPON
C
EXPON = ABS( ET )
A = MT
BASE = B
IF ( ET.LT.0 ) BASE = ONE/BASE
C WHILE ( not EXPON = 0 ) DO
60 IF ( EXPON.NE.0 ) THEN
IF ( MOD( EXPON, 2 ).EQ.0 ) THEN
BASE = BASE*BASE
EXPON = EXPON/2
ELSE
A = A*BASE
EXPON = EXPON - 1
END IF
GO TO 60
END IF
C END WHILE 60
C
RETURN
C *** Last line of MC01SY ***
END
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