Method: BigMathR::Const::PI.euler

Defined in:
lib/bigdecimal/math_r/const/PI_euler.rb

.euler(prec) ⇒ BigDecimal

Implement by Euler’s formula.

Examples:

BigMathR::Const::PI.euler(20)
#=> 0.31415926535897932385e1

Parameters:

  • prec (Integer) —

    Arbitrary precision

Returns:

  • (BigDecimal) —

    Constant PI

Raises:

  • (TypeError) —

    not an Integer

  • (RangeError) —

    Zero or negative precision



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# File 'lib/bigdecimal/math_r/const/PI_euler.rb', line 18

def euler(prec)
  raise TypeError, "precision must be an Integer" unless prec.class == Integer
  raise RangeError, "Zero or negative precision" if prec <= 0
  n = BigDecimal.double_fig + prec
  one = BigDecimal(1)
  two = BigDecimal(2)
  s = BigDecimal(0)
  t = one
  t1 = BigDecimal(0)
  t2 = one
  n = prec + BigDecimal.double_fig
  while t.nonzero? && ((m = n - (s.exponent - t.exponent).abs) > 0)
    m = BigDecimal.double_fig if m < BigDecimal.double_fig
    s = s + t
    t1 = t1 + one;  t = t.mult(t1, m)
    t2 = t2 + two;  t = t.div(t2, m)
  end
  two.mult(s, prec)
end