xadd.f
SUBROUTINE XADD (X, IX, Y, IY, Z, IZ, IERROR)
C***BEGIN PROLOGUE XADD
C***PURPOSE To provide single-precision floating-point arithmetic
C with an extended exponent range.
C***LIBRARY SLATEC
C***CATEGORY A3D
C***TYPE SINGLE PRECISION (XADD-S, DXADD-D)
C***KEYWORDS EXTENDED-RANGE SINGLE-PRECISION ARITHMETIC
C***AUTHOR Lozier, Daniel W., (National Bureau of Standards)
C Smith, John M., (NBS and George Mason University)
C***DESCRIPTION
C REAL X, Y, Z
C INTEGER IX, IY, IZ
C
C FORMS THE EXTENDED-RANGE SUM (Z,IZ) =
C (X,IX) + (Y,IY). (Z,IZ) IS ADJUSTED
C BEFORE RETURNING. THE INPUT OPERANDS
C NEED NOT BE IN ADJUSTED FORM, BUT THEIR
C PRINCIPAL PARTS MUST SATISFY
C RADIX**(-2L).LE.ABS(X).LE.RADIX**(2L),
C RADIX**(-2L).LE.ABS(Y).LE.RADIX**(2L).
C
C***SEE ALSO XSET
C***REFERENCES (NONE)
C***ROUTINES CALLED XADJ
C***COMMON BLOCKS XBLK2
C***REVISION HISTORY (YYMMDD)
C 820712 DATE WRITTEN
C 881020 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 920127 Revised PURPOSE section of prologue. (DWL)
C***END PROLOGUE XADD