(setq least-positive-double-float  1.0e-30)
;Reading at top level.
;Reading in base 10 in package USER with standard Zetalisp readtable.

(describe foo)
0.0 is a flonum.
  Excess-2000 exponent #o3777, 31-bit mantissa #o0 (including sign bit)

0.0
(- foo 3.3)
0.0

; foo is created inside the ALLROOTS command in macsyma.
; only vanilla user level floating point arithmetic is done.