anchor.diff:  
   C----------MATRIX COEFFICIENTS FOR LINEAR EQUATION.
         DOUBLE PRECISION a(nnuc,nnuc)!Coefficient array.
  -      REAL    b(nnuc)              !Right-hand vector w/o manipulation.
  +      REAL    b_(nnuc)              !Right-hand vector w/o manipulation.
         REAL    y(nnuc)              !Solution vector.
   
   C----------COUNTERS AND FLAGS.
  
positive.code:       mbad = 0                     !No errors yet.
  C..........SET RIGHT-HAND AND SOLUTION VECTORS TO INITIAL VALUES.
        DO i = 1,isize
          x(i) = b(i)                !Right-hand vector.
          y(i) = 0.                  !Solution vector.
        END DO
  C..........SAVE MATRIX.
  
negative.code: 
  C----------COMPONENTS OF MATRIX EQUATION.
        DOUBLE PRECISION a(nnuc,nnuc)!Relates y(t-dt) to y(t).
        REAL    b_(nnuc)              !Contains y0 in inverse order.
        REAL    yx(nnuc)             !yy in reverse order.
  
  C----------COUNTERS AND FLAGS.
  