, ...)
or approximate representation, which means that the real
is represented by a rational (with a denominator that is a power
of the basis of the representation) close to the real.
Inside Xcas, the standard scientific notation is used
for approximate representation, that is a mantissa (with a point
as decimal separator) optionnally followed by the letter e
and an integer exponent.
Note that the real number 10-4 is an exact number but 1e - 4 is an approximate representation of this number.