mirror of
https://git.planet-casio.com/Lephenixnoir/OpenLibm.git
synced 2025-01-01 06:23:39 +01:00
113 lines
3.3 KiB
Fortran
113 lines
3.3 KiB
Fortran
*DECK DXC210
|
|
SUBROUTINE DXC210 (K, Z, J, IERROR)
|
|
C***BEGIN PROLOGUE DXC210
|
|
C***PURPOSE To provide double-precision floating-point arithmetic
|
|
C with an extended exponent range.
|
|
C***LIBRARY SLATEC
|
|
C***CATEGORY A3D
|
|
C***TYPE DOUBLE PRECISION (XC210-S, DXC210-D)
|
|
C***KEYWORDS EXTENDED-RANGE DOUBLE-PRECISION ARITHMETIC
|
|
C***AUTHOR Lozier, Daniel W., (National Bureau of Standards)
|
|
C Smith, John M., (NBS and George Mason University)
|
|
C***DESCRIPTION
|
|
C INTEGER K, J
|
|
C DOUBLE PRECISION Z
|
|
C
|
|
C GIVEN K THIS SUBROUTINE COMPUTES J AND Z
|
|
C SUCH THAT RADIX**K = Z*10**J, WHERE Z IS IN
|
|
C THE RANGE 1/10 .LE. Z .LT. 1.
|
|
C THE VALUE OF Z WILL BE ACCURATE TO FULL
|
|
C DOUBLE-PRECISION PROVIDED THE NUMBER
|
|
C OF DECIMAL PLACES IN THE LARGEST
|
|
C INTEGER PLUS THE NUMBER OF DECIMAL
|
|
C PLACES CARRIED IN DOUBLE-PRECISION DOES NOT
|
|
C EXCEED 60. DXC210 IS CALLED BY SUBROUTINE
|
|
C DXCON WHEN NECESSARY. THE USER SHOULD
|
|
C NEVER NEED TO CALL DXC210 DIRECTLY.
|
|
C
|
|
C***SEE ALSO DXSET
|
|
C***REFERENCES (NONE)
|
|
C***ROUTINES CALLED XERMSG
|
|
C***COMMON BLOCKS DXBLK3
|
|
C***REVISION HISTORY (YYMMDD)
|
|
C 820712 DATE WRITTEN
|
|
C 890126 Revised to meet SLATEC CML recommendations. (DWL and JMS)
|
|
C 901019 Revisions to prologue. (DWL and WRB)
|
|
C 901106 Changed all specific intrinsics to generic. (WRB)
|
|
C Corrected order of sections in prologue and added TYPE
|
|
C section. (WRB)
|
|
C CALLs to XERROR changed to CALLs to XERMSG. (WRB)
|
|
C 920127 Revised PURPOSE section of prologue. (DWL)
|
|
C***END PROLOGUE DXC210
|
|
DOUBLE PRECISION Z
|
|
INTEGER K, J
|
|
INTEGER NLG102, MLG102, LG102
|
|
COMMON /DXBLK3/ NLG102, MLG102, LG102(21)
|
|
SAVE /DXBLK3/
|
|
C
|
|
C THE CONDITIONS IMPOSED ON NLG102, MLG102, AND LG102 BY
|
|
C THIS SUBROUTINE ARE
|
|
C
|
|
C (1) NLG102 .GE. 2
|
|
C
|
|
C (2) MLG102 .GE. 1
|
|
C
|
|
C (3) 2*MLG102*(MLG102 - 1) .LE. 2**NBITS - 1
|
|
C
|
|
C THESE CONDITIONS MUST BE MET BY APPROPRIATE CODING
|
|
C IN SUBROUTINE DXSET.
|
|
C
|
|
C***FIRST EXECUTABLE STATEMENT DXC210
|
|
IERROR=0
|
|
IF (K.EQ.0) GO TO 70
|
|
M = MLG102
|
|
KA = ABS(K)
|
|
KA1 = KA/M
|
|
KA2 = MOD(KA,M)
|
|
IF (KA1.GE.M) GO TO 60
|
|
NM1 = NLG102 - 1
|
|
NP1 = NLG102 + 1
|
|
IT = KA2*LG102(NP1)
|
|
IC = IT/M
|
|
ID = MOD(IT,M)
|
|
Z = ID
|
|
IF (KA1.GT.0) GO TO 20
|
|
DO 10 II=1,NM1
|
|
I = NP1 - II
|
|
IT = KA2*LG102(I) + IC
|
|
IC = IT/M
|
|
ID = MOD(IT,M)
|
|
Z = Z/M + ID
|
|
10 CONTINUE
|
|
JA = KA*LG102(1) + IC
|
|
GO TO 40
|
|
20 CONTINUE
|
|
DO 30 II=1,NM1
|
|
I = NP1 - II
|
|
IT = KA2*LG102(I) + KA1*LG102(I+1) + IC
|
|
IC = IT/M
|
|
ID = MOD(IT,M)
|
|
Z = Z/M + ID
|
|
30 CONTINUE
|
|
JA = KA*LG102(1) + KA1*LG102(2) + IC
|
|
40 CONTINUE
|
|
Z = Z/M
|
|
IF (K.GT.0) GO TO 50
|
|
J = -JA
|
|
Z = 10.0D0**(-Z)
|
|
GO TO 80
|
|
50 CONTINUE
|
|
J = JA + 1
|
|
Z = 10.0D0**(Z-1.0D0)
|
|
GO TO 80
|
|
60 CONTINUE
|
|
C THIS ERROR OCCURS IF K EXCEEDS MLG102**2 - 1 IN MAGNITUDE.
|
|
C
|
|
CALL XERMSG ('SLATEC', 'DXC210', 'K too large', 208, 1)
|
|
IERROR=208
|
|
RETURN
|
|
70 CONTINUE
|
|
J = 0
|
|
Z = 1.0D0
|
|
80 RETURN
|
|
END
|