ADAS Subroutine xxbasa

      subroutine xxbasa(a , ia , b , ib , base , c  , ic)
c-----------------------------------------------------------------------
c
c  ****************** fortran77 subroutine: xxbasa *********************
c
c  purpose : to add two numbers, given in the form a*base^ia and
c            b*base^ib, where the base must be the same.
c
c  calling program: general use
c
c  subroutine:
c
c  input : (r*8)   a        = mantissa of number
c  input : (i*4)   ia       = characteristic of number
c  input : (r*8)   b        = mantissa of number
c  input : (i*4)   ib       = characteristic of number
c  input : (r*8)   base     = base of number system
c
c  output: (r*8)   c        = mantissa of answer
c  output: (i*4)   ic       = characteristic of answer
c
c routines:
c          routine    source    brief description
c          ------------------------------------------------------------
c          xxbass     adas      to scale a number to a base
c          i4unit     adas      fetch unit number for output of messages
c
c author:  Hugh Summers
c          JET K1/1/61
c          Tel. 01235-46-4459
c date:    14-05-2008
c
c
c version  : 1.1
c date     : 14-05-2008
c modified : Hugh Summers
c              - first version.
c-----------------------------------------------------------------------
      INTEGER             IA,          IB,          IC
      REAL*8              A,           B,           BASE,        C