Module: Flt::DecNum::Trigonometry

Includes:
Trigonometry::Support
Defined in:
lib/flt/trigonometry.rb

Constant Summary collapse

PI_MARGIN = 
10

Class Attribute Summary collapse

Instance Method Summary collapse

Methods included from Trigonometry::Support

iarccot

Class Attribute Details

.pi_cache ⇒ Object

Returns the value of attribute pi_cache.



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# File 'lib/flt/trigonometry.rb', line 616

def pi_cache
  @pi_cache
end

.pi_cache_digits ⇒ Object

Returns the value of attribute pi_cache_digits.



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# File 'lib/flt/trigonometry.rb', line 616

def pi_cache_digits
  @pi_cache_digits
end

Instance Method Details

#pi(round_digits = nil) ⇒ Object 



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# File 'lib/flt/trigonometry.rb', line 619

def pi(round_digits=nil)
  round_digits ||= self.precision
  digits = round_digits
    if Trigonometry.pi_cache_digits <= digits # we need at least one more truncated digit
       continue = true
       while continue
         margin = PI_MARGIN # margin to reduce recomputing with more digits to avoid ending in 0 or 5
         digits += margin + 1
         fudge = 10
         unity = 10**(digits+fudge)
         v = 4*(4*iarccot(5, unity) - iarccot(239, unity))
         v = v.to_s[0,digits]
         # if the last digit is 0 or 5 the truncated value may not be good for rounding
         loop do
           #last_digit = v%10
           last_digit = v[-1,1].to_i
           continue = (last_digit==5 || last_digit==0)
           if continue && margin>0
             # if we have margin we back-up one digit
             margin -= 1
             v = v[0...-1]
           else
             break
           end
         end
       end
       Trigonometry.pi_cache_digits = digits + margin - PI_MARGIN # @pi_cache.size
       Trigonometry.pi_cache = v # DecNum(+1, v, 1-digits) # cache truncated value
    end
    # Now we avoid rounding too much because it is slow
    l = round_digits + 1
    while (l<Num[16]::Trigonometry.pi_cache_digits) && [0,5].include?(Trigonometry.pi_cache[l-1,1].to_i)
      l += 1
    end
    v = Trigonometry.pi_cache[0,l]
    num_class.context(self, :precision=>round_digits){+num_class.Num(+1,v.to_i,1-l)}
end