module BigMath

def E(prec)


#=> "0.271828182845904523536028752390026306410273E1"
BigMath::E(10).to_s

digits of precision, +numeric+.
Computes e (the base of natural logarithms) to the specified number of

E(numeric) -> BigDecimal
call-seq: 
def E(prec)
  raise ArgumentError, "Zero or negative precision for E" if prec <= 0
  n    = prec + BigDecimal.double_fig
  one  = BigDecimal("1")
  y  = one
  d  = y
  z  = one
  i  = 0
  while d.nonzero? && ((m = n - (y.exponent - d.exponent).abs) > 0)
    m = BigDecimal.double_fig if m < BigDecimal.double_fig
    i += 1
    z *= i
    d  = one.div(z,m)
    y += d
  end
  y
end