continued fraction
Mathworld





a

0


+









b

1












a

1


+









b

2












a

2


+









b

3












a

3


+
⋱

















{\displaystyle a_{0}+{\cfrac {b_{1}}{a_{1}+{\cfrac {b_{2}}{a_{2}+{\cfrac {b_{3}}{a_{3}+\ddots }}}}}}}


The task is to write a program which generates such a number and prints a real representation of it. The code should be tested by calculating and printing the square root of 2, Napier's Constant, and Pi, using the following coefficients:

For the square root of 2, use 




a

0


=
1


{\displaystyle a_{0}=1}

 then 




a

N


=
2


{\displaystyle a_{N}=2}

. 




b

N




{\displaystyle b_{N}}

 is always 



1


{\displaystyle 1}

.







2


=
1
+








1









2
+








1









2
+








1









2
+
⋱

















{\displaystyle {\sqrt {2}}=1+{\cfrac {1}{2+{\cfrac {1}{2+{\cfrac {1}{2+\ddots }}}}}}}


For Napier's Constant, use 




a

0


=
2


{\displaystyle a_{0}=2}

, then 




a

N


=
N


{\displaystyle a_{N}=N}

. 




b

1


=
1


{\displaystyle b_{1}=1}

 then 




b

N


=
N
−
1


{\displaystyle b_{N}=N-1}

.





e
=
2
+








1









1
+








1









2
+








2









3
+








3









4
+
⋱






















{\displaystyle e=2+{\cfrac {1}{1+{\cfrac {1}{2+{\cfrac {2}{3+{\cfrac {3}{4+\ddots }}}}}}}}}


For Pi, use 




a

0


=
3


{\displaystyle a_{0}=3}

 then 




a

N


=
6


{\displaystyle a_{N}=6}

. 




b

N


=
(
2
N
−
1

)

2




{\displaystyle b_{N}=(2N-1)^{2}}

.





π
=
3
+








1









6
+








9









6
+








25









6
+
⋱

















{\displaystyle \pi =3+{\cfrac {1}{6+{\cfrac {9}{6+{\cfrac {25}{6+\ddots }}}}}}}




See also

   Continued fraction/Arithmetic for tasks that do arithmetic over continued fractions.


Public Const precision = 10000
Private Function continued_fraction(steps As Integer, rid_a As String, rid_b As String) As Double
    Dim res As Double
    res = 0
    For n = steps To 1 Step -1
       res = Application.Run(rid_b, n) / (Application.Run(rid_a, n) + res)
    Next n
    continued_fraction = Application.Run(rid_a, 0) + res
End Function
 
Function sqr2_a(n As Integer) As Integer
    sqr2_a = IIf(n = 0, 1, 2)
End Function
 
Function sqr2_b(n As Integer) As Integer
    sqr2_b = 1
End Function
 
Function nap_a(n As Integer) As Integer
    nap_a = IIf(n = 0, 2, n)
End Function
 
Function nap_b(n As Integer) As Integer
    nap_b = IIf(n = 1, 1, n - 1)
End Function
 
Function pi_a(n As Integer) As Integer
    pi_a = IIf(n = 0, 3, 6)
End Function
 
Function pi_b(n As Integer) As Long
    pi_b = IIf(n = 1, 1, (2 * n - 1) ^ 2)
End Function
 
Public Sub main()
    Debug.Print "Precision:", precision
    Debug.Print "Sqr(2):", continued_fraction(precision, "sqr2_a", "sqr2_b")
    Debug.Print "Napier:", continued_fraction(precision, "nap_a", "nap_b")
    Debug.Print "Pi:", continued_fraction(precision, "pi_a", "pi_b")
End Sub