Source code in the basic programming language

# Basic-256 ver 1.1.4
# iterative Fibonacci sequence
# Matches sequence A000045 in the OEIS, https://oeis.org/A000045/list

# Return the Nth Fibonacci number

input "N = ",f
limit = 500                        # set upper limit - can be changed, removed
f = int(f)
if f > limit then f = limit        
a = 0 : b = 1 : c = 0 : n = 0      # initial values


while n < f
    print n + chr(9) + c   # chr(9) = tab
    a = b
    b = c
    c = a + b  
    n += 1
        
end while

print " "
print n + chr(9) + c

      PRINT FNfibonacci_r(1),  FNfibonacci_i(1)
      PRINT FNfibonacci_r(13), FNfibonacci_i(13)
      PRINT FNfibonacci_r(26), FNfibonacci_i(26)
      END
      
      DEF FNfibonacci_r(N)
      IF N < 2 THEN = N
      = FNfibonacci_r(N-1) + FNfibonacci_r(N-2)
      
      DEF FNfibonacci_i(N)
      LOCAL F, I, P, T
      IF N < 2 THEN = N
      P = 1
      FOR I = 1 TO N
        T = F
        F += P
        P = T
      NEXT
      = F


10 print "Enter a ";
20 print "number ";
30 print "greater ";
40 print "than 1";
50 print " and less";
60 print " than 25";
70 input z
80 b=1
90 a=0
100 n=2
110 f=a+b
120 a=b
130 b=f
140 n=n+1
150 if n-z-1 goto 110
160 print "The ";
170 print z ;
180 print "th ";
190 print "Fibonacci ";
200 print "Number is ";
210 print f


100 cls
110 for i = 0 to 20 : print fibor(i); : next i
120 print
130 for i = 0 to 20 : print fiboi(i); : next i
140 print
150 for i = 0 to 20 : print fiboa(i); : next i
160 end
170 sub fibor(n) : 'Recursive
180   if n < 2 then
190     fibor = n
200   else
210     fibor = fibor(n-1)+fibor(n-2)
220   endif
230 end sub
240 sub fiboi(n) : 'Iterative
250   n1 = 0
260   n2 = 1
270   for k = 1 to abs(n)
280     sum = n1+n2
290     n1 = n2
300     n2 = sum
310   next k
320   if n < 0 then
330     fiboi = n1*((-1)^((-n)+1))
340   else
350     fiboi = n1
360   endif
370 end sub
380 sub fiboa(n) : 'Analytic
390   fiboa = int(0.5+(((sqr 5+1)/2)^n)/sqr 5)
400 end sub


100 PRINT CHR$(147); CHR$(18); "****      FIBONACCI GENERATOR       ****"
110 INPUT "MIN, MAX"; N1, N2
120 IF N1 > N2 THEN T = N1: N1 = N2: N2 = T
130 A = 0: B = 1: S = SGN(N1)
140 FOR I = S TO N1 STEP S
150 : IF S > 0 THEN T = A + B: A = B: B = T
160 : IF S < 0 THEN T = B - A: B = A: A = T
170 NEXT I
180 PRINT
190 PRINT STR$(A); : REM STR$() PREVENTS TRAILING SPACE
200 IF N2 = N1 THEN 250
210 FOR I = N1 + 1 TO N2
220 : T = A + B: A = B: B = T
230 : PRINT ","; STR$(A);
240 NEXT I
250 PRINT


let a = 1
let b = 1

print "Fibonacci Sequence"

for i = 0 to 20

	let s = a + b
	let a = b
	let b = s

	print s

next i


'Fibonacci extended
'Freebasic version 24  Windows
Dim Shared ADDQmod(0 To 19) As Ubyte
Dim Shared ADDbool(0 To 19) As Ubyte

For z As Integer=0 To 19
    ADDQmod(z)=(z Mod 10+48)
    ADDbool(z)=(-(10<=z))
Next z 

Function plusINT(NUM1 As String,NUM2 As String) As String
    Dim As Byte flag
    #macro finish()
    three=Ltrim(three,"0")
    If three="" Then Return "0"
    If flag=1 Then Swap NUM2,NUM1
    Return three
    Exit Function
    #endmacro
    var lenf=Len(NUM1)
    var lens=Len(NUM2)
    If lens>lenf Then 
        Swap NUM2,NUM1
        Swap lens,lenf
        flag=1
    End If
    
    var diff=lenf-lens-Sgn(lenf-lens)
    var three="0"+NUM1
    var two=String(lenf-lens,"0")+NUM2
    Dim As Integer n2
    Dim As Ubyte addup,addcarry
    
    addcarry=0
    
    For n2=lenf-1 To diff Step -1 
        addup=two[n2]+NUM1[n2]-96
        three[n2+1]=addQmod(addup+addcarry)
        addcarry=addbool(addup+addcarry)
    Next n2 
    If addcarry=0 Then 
        finish()
    End If
    If n2=-1 Then 
        three[0]=addcarry+48
        finish()
    End If
    
    For n2=n2 To 0 Step -1 
        addup=two[n2]+NUM1[n2]-96
        three[n2+1]=addQmod(addup+addcarry)
        addcarry=addbool(addup+addcarry)
    Next n2
    three[0]=addcarry+48
    finish()
End Function

Function  fibonacci(n As Integer) As String
    Dim As String sl,l,term
    sl="0": l="1"
    If n=1 Then Return "0"
    If n=2 Then Return "1"
    n=n-2
    For x As Integer= 1 To n
        term=plusINT(l,sl)
        sl=l
        l=term
    Next x
    Function =term
End Function

'==============  EXAMPLE ===============
print "THE SEQUENCE TO 10:"
print
For n As Integer=1 To 10
    Print "term";n;": "; fibonacci(n)
Next n
print
print "Selected Fibonacci number"
print "Fibonacci 500"
print
print fibonacci(500)
Sleep

define a = 1, b = 1, s = 0, i = 0

cls

print "Fibonacci Sequence"

do

	let s = a + b
	let a = b
	let b = s
	+1 i

	print s

loop i < 20

pause
end


window 1, @"Fibonacci Sequence", (0,0,480,620)

local fn Fibonacci( n as long ) as long
  static long s1
  static long s2
  long        temp
  
  if ( n < 2 )
    s1 = n
    exit fn
  else
    temp = s1 + s2
    s2 = s1
    s1 = temp
    exit fn
  end if
end fn = s1

long i
CFTimeInterval t

t = fn CACurrentMediaTime

for i = 0 to 40
  print i;@".\t";fn Fibonacci(i)
next i

print : printf @"Compute time: %.3f ms",(fn CACurrentMediaTime-t)*1000

HandleEvents

local fn Fibonacci( n as NSInteger ) as NSInteger
NSInteger result
if n < 2 then result = n : exit fn
result = fn Fibonacci( n-1 ) + fn Fibonacci( n-2 )
end fn = result

window 1

NSInteger i
CFTimeInterval t

t = fn CACurrentMediaTime
for i = 0 to 40
print i;@".\t";fn Fibonacci(i)
next
print : printf @"Compute time: %.3f ms",(fn CACurrentMediaTime-t)*1000

HandleEvents

'
' Compute nth Fibonacci number
'
' open a window for display
OPENW 1
CLEARW 1
' Display some fibonacci numbers
' Fib(46) is the largest number GFA Basic can reach
' (long integers are 4 bytes)
FOR i%=0 TO 46
  PRINT "fib(";i%;")=";@fib(i%)
NEXT i%
' wait for a key press and tidy up
~INP(2)
CLOSEW 1
'
' Function to compute nth fibonacci number
' n must be in range 0 to 46, inclusive
'
FUNCTION fib(n%)
  LOCAL n0%,n1%,nn%,i%
  n0%=0
  n1%=1
  SELECT n%
  CASE 0
    RETURN n0%
  CASE 1
    RETURN n1%
  DEFAULT
    FOR i%=2 TO n%
      nn%=n0%+n1%
      n0%=n1%
      n1%=nn%
    NEXT i%
    RETURN nn%
  ENDSELECT
ENDFUNC


10 ' SAVE"FIBONA", A
20 ' Secuencia de Fibonacci
30 ' Var
40 DEFDBL D
50 IMAXFIBO% = 76
60 DNUM1 = 1: DNUM2 = DNUM1
70 CLS
80 PRINT "Este programa calcula la serie de Fibonacci."
90 PRINT DNUM1; DNUM2;
100 FOR I% = 1 TO IMAXFIBO%
110   DNUM3 = DNUM1 + DNUM2
120   PRINT DNUM3;
130   DNUM1 = DNUM2: DNUM2 = DNUM3
140 NEXT I%
150 PRINT
160 PRINT "Fin de la ejecución del programa."
170 END

10 ' SAVE"FIBINF", A
20 ' Secuencia de Fibonacci mediante la fórmula de Binet
30 ' Var
40 DEFDBL D
50 IMAXFIBO% = 77
60 DSQR5 = SQR(5)
70 DPIV1 = (1 + DSQR5) / 2
80 DPIV2 = (1 - DSQR5) / 2
90 DNUM1 = DPIV1: DNUM2 = DPIV2
100 CLS
110 PRINT "Este programa calcula la serie de Fibonacci."
120 FOR I% = 1 TO IMAXFIBO%
130   DNUM1 = DNUM1 * DPIV1
140   DNUM2 = DNUM2 * DPIV2
150   PRINT FIX(((DNUM1 - DNUM2) / DSQR5)+.5);
160 NEXT I%
170 PRINT
180 PRINT "Fin de la ejecución del programa."
190 END

 10 INPUT N
 20 A=0
 30 B=1
 40 FOR I=2 TO N
 50 C=B
 60 B=A+B
 70 A=C
 80 NEXT I
 90 PRINT B
100 END


100 PROGRAM "Fibonac.bas"
110 FOR I=0 TO 20
120   PRINT "F";I,FIB(I)
130 NEXT
140 DEF FIB(N)
150   NUMERIC I
160   LET A=0:LET B=1
170   FOR I=1 TO N
180     LET T=A+B:LET A=B:LET B=T
190   NEXT
200   LET FIB=A
210 END DEF

for i = 0 to 15
    print fiboR(i),fiboI(i)
next i
 
function fiboR(n)
    if n <= 1 then
        fiboR = n
    else
        fiboR = fiboR(n-1) + fiboR(n-2)
    end if
end function
 
function fiboI(n)
    a = 0
    b = 1
    for i = 1 to n
        temp = a + b
        a = b
        b = temp
    next i
    fiboI = a
end function

print "Rosetta Code - Fibonacci sequence": print
print "  n             Fn"
for x=-12 to 12 '68 max
    print using("### ", x); using("##############", FibonacciTerm(x))
next x
print
[start]
input "Enter a term#: "; n$
n$=lower$(trim$(n$))
if n$="" then print "Program complete.": end
print FibonacciTerm(val(n$))
goto [start]

function FibonacciTerm(n)
    n=int(n)
    FTa=0: FTb=1: FTc=-1
    select case
        case n=0  : FibonacciTerm=0  : exit function
        case n=1  : FibonacciTerm=1  : exit function
        case n=-1 : FibonacciTerm=-1 : exit function
        case n>1
            for x=2 to n
                FibonacciTerm=FTa+FTb
                FTa=FTb: FTb=FibonacciTerm
            next x
            exit function
        case n<-1
            for x=-2 to n step -1
                FibonacciTerm=FTa+FTc
                FTa=FTc: FTc=FibonacciTerm
            next x
            exit function
    end select
end function

' Fibonacci sequence - 31/07/2018
  n = 139
  f1 = 0
  f2 = 1
  TextWindow.WriteLine("fibo(0)="+f1)
  TextWindow.WriteLine("fibo(1)="+f2)
  For i = 2 To n
    f3 = f1 + f2
    TextWindow.WriteLine("fibo("+i+")="+f3)
    f1 = f2
    f2 = f3
  EndFor

' Fibonacci sequence - Binet's Formula - 31/07/2018
  n = 69
  sq5=Math.SquareRoot(5)
  phi1=(1+sq5)/2
  phi2=(1-sq5)/2
  phi1n=phi1
  phi2n=phi2
  For i = 2 To n
    phi1n=phi1n*phi1
    phi2n=phi2n*phi2
    TextWindow.Write(Math.Floor((phi1n-phi2n)/sq5)+" ")
  EndFor

110 REM THE ARRAY F HOLDS THE FIBONACCI NUMBERS
120 DIM F(22)
130 LET F(0) = 0
140 LET F(1) = 1
150 LET N = 1
160 REM COMPUTE THE NEXT FIBBONACCI NUMBER
170 LET F(N+1) = F(N)+F(N-1)
180 LET N = N+1
190 PRINT F(N-2);
200 REM STOP AFTER PRINTING  20 NUMBERS
210 IF N < 22 THEN 170
220 END


100 CLS
110 FOR N = 0 TO 15: GOSUB 130: PRINT FIBOI; : NEXT N
120 END
130 REM Iterative Fibonacci sequence
140 N1 = 0
150 N2 = 1
160 FOR K = 1 TO ABS(N)
170   SUM = N1 + N2
180   N1 = N2
190   N2 = SUM
200 NEXT K
210 IF N < 0 THEN FIBOI = N1 * ((-1) ^ ((-N) + 1)) ELSE FIBOI = N1
220 RETURN


10 REM FIBONACCI SEQUENCE
20 INPUT "ENTER N FOR FIB(N)"N
30 LET A=0,B=1
40 FOR I=2 TO N
50 LET T=B,B=A+B,A=T
60 NEXT I
70 PRINT B
80 STOP


FUNCTION fibonacci (n AS LONG) AS QUAD
    DIM u AS LONG, a AS LONG, L0 AS LONG, outP AS QUAD
    STATIC fibNum() AS QUAD

    u = UBOUND(fibNum)
    a = ABS(n)

    IF u < 1 THEN
        REDIM fibNum(1)
        fibNum(1) = 1
        u = 1
    END IF

    SELECT CASE a
        CASE 0 TO 92
            IF a > u THEN
                REDIM PRESERVE fibNum(a)
                FOR L0 = u + 1 TO a
                    fibNum(L0) = fibNum(L0 - 1) + fibNum(L0 - 2)
                    IF 88 = L0 THEN fibNum(88) = fibNum(88) + 1
                NEXT
            END IF
            IF n < 0 THEN
                fibonacci = fibNum(a) * ((-1)^(a+1))
            ELSE
                fibonacci = fibNum(a)
            END IF
        CASE ELSE
            'Even without the above-mentioned bug, we're still limited to
            'F(+/-92), due to data type limits. (F(93) = &hA94F AD42 221F 2702)
            ERROR 6
    END SELECT
END FUNCTION

FUNCTION PBMAIN () AS LONG
    DIM n AS LONG
    #IF NOT %DEF(%PB_CC32)
        OPEN "out.txt" FOR OUTPUT AS 1
    #ENDIF
    FOR n = -92 TO 92
        #IF %DEF(%PB_CC32)
            PRINT STR$(n); ": "; FORMAT$(fibonacci(n), "#")
        #ELSE
            PRINT #1, STR$(n) & ": " & FORMAT$(fibonacci(n), "#")
        #ENDIF
    NEXT
    CLOSE
END FUNCTION

Macro Fibonacci (n)
	Int((Pow(((1+Sqr(5))/2),n)-Pow(((1-Sqr(5))/2),n))/Sqr(5))
EndMacro

Procedure FibonacciReq(n)
  If n<2
    ProcedureReturn n
  Else
    ProcedureReturn FibonacciReq(n-1)+FibonacciReq(n-2)
  EndIf
EndProcedure

Procedure Fibonacci(n)
  Static NewMap Fib.i()
  Protected FirstRecursion
  
  If MapSize(Fib())= 0        ; Init the hash table the first run
    Fib("0")=0: Fib("1")=1
    FirstRecursion = #True
  EndIf
 
  If n >= 2
    Protected.s s=Str(n)
    If Not FindMapElement(Fib(),s)  ; Calculate only needed parts
      Fib(s)= Fibonacci(n-1)+Fibonacci(n-2)
    EndIf
    n = Fib(s)  
  EndIf
  If FirstRecursion ; Free the memory when finalizing the first call
    ClearMap(Fib())
  EndIf
  ProcedureReturn n
EndProcedure

_DEFINE F AS _UNSIGNED _INTEGER64
CLS
PRINT
PRINT "Enter 40 to more easily see the difference in calculation speeds."
PRINT
INPUT "Enter n for Fibonacci(n): ", n
PRINT
PRINT " Analytic Method (Fastest): F("; LTRIM$(STR$(n)); ") ="; fA(n)
PRINT "Iterative Method    (Fast): F("; LTRIM$(STR$(n)); ") ="; fI(n)
PRINT "Recursive Method    (Slow): F("; LTRIM$(STR$(n)); ") ="; fR(n)
END

' === Analytic Fibonacci Function (Fastest)
FUNCTION fA (n)
  fA = INT(0.5 + (((SQR(5) + 1) / 2) ^ n) / SQR(5))
END FUNCTION

' === Iterative Fibonacci Function (Fast)
FUNCTION fI (n)
  FOR i = 1 TO n
    IF i < 3 THEN a = 1: b = 1
    t = fI + b: fI = b: b = t
  NEXT
END FUNCTION

' === Recursive Fibonacci function (Slow)
FUNCTION fR (n)
  IF n <= 1 THEN
    fR = n
  ELSE
    fR = fR(n - 1) + fR(n - 2)
  END IF
END FUNCTION


DIM F(80) AS DOUBLE 'FibRus.bas DANILIN
F(1) = 0: F(2) = 1
'OPEN "FibRus.txt" FOR OUTPUT AS #1
FOR i = 3 TO 80
    F(i) = F(i-1)+F(i-2)
NEXT i

FOR i = 1 TO 80
    f$ = STR$(F(i)): LF = 22 - LEN(f$)
    n$ = ""
    FOR j = 1 TO LF: n$ = " " + n$: NEXT
    f$ = n$ + f$
    PRINT i, f$: ' PRINT #1, i, f$
NEXT i


FUNCTION itFib (n)
    n1 = 0
    n2 = 1
    FOR k = 1 TO ABS(n)
        sum = n1 + n2
        n1 = n2
        n2 = sum
    NEXT k
    IF n < 0 THEN
        itFib = n1 * ((-1) ^ ((-n) + 1))
    ELSE
        itFib = n1
    END IF
END FUNCTION


DECLARE FUNCTION fibonacci& (n AS INTEGER)

REDIM SHARED fibNum(1) AS LONG

fibNum(1) = 1

'*****sample inputs*****
PRINT fibonacci(0)      'no calculation needed
PRINT fibonacci(13)     'figure F(2)..F(13)
PRINT fibonacci(-42)    'figure F(14)..F(42)
PRINT fibonacci(47)     'error: too big
'*****sample inputs*****

FUNCTION fibonacci& (n AS INTEGER)
    DIM a AS INTEGER
    a = ABS(n)
    SELECT CASE a
        CASE 0 TO 46
            SHARED fibNum() AS LONG
            DIM u AS INTEGER, L0 AS INTEGER
            u = UBOUND(fibNum)
            IF a > u THEN
                REDIM PRESERVE fibNum(a) AS LONG
                FOR L0 = u + 1 TO a
                    fibNum(L0) = fibNum(L0 - 1) + fibNum(L0 - 2)
                NEXT
            END IF
            IF n < 0 THEN
                fibonacci = fibNum(a) * ((-1) ^ (a + 1))
            ELSE
                fibonacci = fibNum(n)
            END IF
        CASE ELSE
            'limited to signed 32-bit int (LONG)
            'F(47)=&hB11924E1
            ERROR 6 'overflow
    END SELECT
END FUNCTION


FUNCTION recFib (n)
    IF (n < 2) THEN
	recFib = n
    ELSE
	recFib = recFib(n - 1) + recFib(n - 2)
    END IF
END FUNCTION


DATA -1836311903,1134903170,-701408733,433494437,-267914296,165580141,-102334155
DATA 63245986,-39088169,24157817,-14930352,9227465,-5702887,3524578,-2178309
DATA 1346269,-832040,514229,-317811,196418,-121393,75025,-46368,28657,-17711
DATA 10946,-6765,4181,-2584,1597,-987,610,-377,233,-144,89,-55,34,-21,13,-8,5,-3
DATA 2,-1,1,0,1,1,2,3,5,8,13,21,34,55,89,144,233,377,610,987,1597,2584,4181,6765
DATA 10946,17711,28657,46368,75025,121393,196418,317811,514229,832040,1346269
DATA 2178309,3524578,5702887,9227465,14930352,24157817,39088169,63245986
DATA 102334155,165580141,267914296,433494437,701408733,1134903170,1836311903

DIM fibNum(-46 TO 46) AS LONG

FOR n = -46 TO 46
    READ fibNum(n)
NEXT

'*****sample inputs*****
FOR n = -46 TO 46
    PRINT fibNum(n),
NEXT
PRINT
'*****sample inputs*****


100 CLS
110 rem The array F holds the Fibonacci numbers
120 ARRAY f : rem DIM f(22) para Quite BASIC and MSX-BASIC
130 LET f(0) = 0
140 LET f(1) = 1
150 LET n = 1
160 rem Compute the NEXT Fibbonacci number
170 LET f(n+1) = f(n)+f(n-1)
180 LET n = n+1
190 PRINT f(n-2);" ";
200 rem STOP after printing  20 numbers
210 IF n < 22 THEN GOTO 170


for i = 0 to 10
 print i;" ";fibR(i);" ";fibI(i)
next i
end
 
 function fibR(n)
 if n < 2 then fibR = n else fibR = fibR(n-1) + fibR(n-2)
 end function
 
 function fibI(n)
   b = 1
   for i = 1 to n
       t = a + b
       a = b
       b = t
   next i
fibI = a
end function

rem - iterative function to calculate nth fibonacci number
function fibonacci(n = integer) = integer
var f, i, p1, p2 = integer
p1 = 0    
p2 = 1
if n = 0 then
   f = 0
else
   for i = 1 to n
      f = p1 + p2
      p2 = p1
      p1 = f
   next i
end = f

rem - exercise the function
var i = integer
for i = 0 to 10
   print fibonacci(i);
next i

end


 10 INPUT N
 20 PRINT INT (0.5+(((SQR 5+1)/2)**N)/SQR 5)


 10 INPUT N
 20 LET A=0
 30 LET B=1
 40 FOR I=2 TO N
 50 LET C=B
 60 LET B=A+B
 70 LET A=C
 80 NEXT I
 90 PRINT B


 10 INPUT N
 20 LET A=0
 30 LET B=1
 40 GOSUB 70
 50 PRINT B
 60 STOP
 70 IF N=1 THEN RETURN
 80 LET C=B
 90 LET B=A+B
100 LET A=C
110 LET N=N-1
120 GOSUB 70
130 RETURN


FOR i = 0 TO 15
    PRINT fibR(i),fibI(i),fibN(i)
NEXT i

/* Recursive Method */
DEF fibR(n)
    IF n <= 1 THEN
        fibR = n
    ELSE
        fibR = fibR(n-1) + fibR(n-2)
    ENDIF
END DEF

/* Iterative Method */
DEF fibI(n)
    a = 0
    b = 1
    FOR i = 1 TO n
        temp = a + b
        a = b
        b = temp
    NEXT i
    fibI = a
END DEF

/* N-th Term Method */
DEF fibN(n)
    uphi = .5 + SQR(5)/2
    lphi = .5 - SQR(5)/2
    fibN = (uphi^n-lphi^n)/SQR(5)
END DEF


Function Fibonacci(n)
   x = 0
   y = 1
   i = 0
   n = ABS(n)
   If n < 2 Then
   Fibonacci = n
   Else
   Do Until (i = n)
      sum = x+y
      x=y
      y=sum
      i=i+1
   Loop
   Fibonacci = x
   End If

End Function


[Y=]
nMin=0
u(n)=u(n-1)+u(n-2)
u(nMin)={1,0}
[TABLE]
n	u(n)
-------	-------
0	0
1	1
2	1
3	2
4	3
5	5
6	8
7	13
8	21
9	34
10	55
11	89
12	144

{0,1
While 1
Disp Ans(1
{Ans(2),sum(Ans
End

Prompt N
.5(1+√(5    //golden ratio
(Ans^N–(-Ans)^-N)/√(5

fib(n)
when(n<2, n, fib(n-1) + fib(n-2))

fib(n)
Func
Local a,b,c,i
0→a
1→b
For i,1,n
  a→c
  b→a
  c+b→b
EndFor
a
EndFunc

10 LET A = 0
20 LET B = 1
30 PRINT "Which F_n do you want?"
40 INPUT N
50 IF N = 0 THEN GOTO 140
60 IF N = 1 THEN GOTO 120
70 LET C = B + A
80 LET A = B
90 LET B = C
100 LET N = N - 1
110 GOTO 60
120 PRINT B
130 END
140 PRINT 0
150 END


10 cls

20 let a = 1
30 let b = 1

40 print "Fibonacci Sequence"

50 rem loop

	60 let s = a + b
	70 let a = b
	80 let b = s
	90 let i = i + 1

	100 print s

120 if i < 20 then 50

130 shell "pause"
140 end


FUNCTION fibonacci (n)
    LET n1 = 0
    LET n2 = 1
    FOR k = 1 TO ABS(n)
        LET sum = n1 + n2
        LET n1 = n2
        LET n2 = sum
    NEXT k
    IF n < 0 THEN
       LET fibonacci = n1 * ((-1) ^ ((-n) + 1))
    ELSE
       LET fibonacci = n1
    END IF
END FUNCTION

PRINT fibonacci(0)      ! 0
PRINT fibonacci(13)     ! 233
PRINT fibonacci(-42)    !-267914296
PRINT fibonacci(47)     ! 2971215073
END


Public Function Fib(ByVal n As Integer) As Variant
    Dim fib0 As Variant, fib1 As Variant, sum As Variant
    Dim i As Integer
    fib0 = 0
    fib1 = 1
    For i = 1 To n
        sum = fib0 + fib1
        fib0 = fib1
        fib1 = sum
    Next i
    Fib = fib0
End Function

Public Function RFib(Term As Integer) As Long
  If Term < 2 Then RFib = Term Else RFib = RFib(Term - 1) + RFib(Term - 2)
End Function

class generator
	dim t1
	dim t2
	dim tn
	dim cur_overflow
	
	Private Sub Class_Initialize
		cur_overflow = false
		t1 = ccur(0)
		t2 = ccur(1)
		tn = ccur(t1 + t2)
	end sub
	
	public default property get generated
		on error resume next

		generated = ccur(tn)
		if err.number <> 0 then 
			generated = cdbl(tn)
			cur_overflow = true
		end if
		t1 = ccur(t2)
		if err.number <> 0 then 
			t1 = cdbl(t2)
			cur_overflow = true
		end if
		t2 = ccur(tn)
		if err.number <> 0 then 
			t2 = cdbl(tn)
			cur_overflow = true
		end if
		tn = ccur(t1+ t2)
		if err.number <> 0 then 
			tn = cdbl(t1) + cdbl(t2)
			cur_overflow = true
		end if
		on error goto 0
	end property
	
	public property get overflow
		overflow = cur_overflow
	end property
		
end class

dim fib
set fib = new generator
dim i
for i = 1 to 100
	wscript.stdout.write " " & fib 
	if fib.overflow then
		wscript.echo
		exit for
	end if
next

Sub fibonacci()
    Const n = 139 
    Dim i As Integer
    Dim f1 As Variant, f2 As Variant, f3 As Variant 'for Decimal
    f1 = CDec(0): f2 = CDec(1) 'for Decimal setting
    Debug.Print "fibo("; 0; ")="; f1
    Debug.Print "fibo("; 1; ")="; f2
    For i = 2 To n
        f3 = f1 + f2
        Debug.Print "fibo("; i; ")="; f3
        f1 = f2
        f2 = f3
    Next i
End Sub 'fibonacci

Function Fib(ByVal n As Integer) As Decimal
    Dim fib0, fib1, sum As Decimal
    Dim i As Integer
    fib0 = 0
    fib1 = 1
    For i = 1 To n
        sum = fib0 + fib1
        fib0 = fib1
        fib1 = sum
    Next
    Fib = fib0
End Function


Function Seq(ByVal Term As Integer)
        If Term < 2 Then Return Term
        Return Seq(Term - 1) + Seq(Term - 2)
End Function


    Function FiboBig(ByVal n As Integer) As BigInteger
        ' Fibonacci sequence with BigInteger
        Dim fibn2, fibn1, fibn As BigInteger
        Dim i As Integer
        fibn = 0
        fibn2 = 0
        fibn1 = 1
        If n = 0 Then
            Return fibn2
        ElseIf n = 1 Then
            Return fibn1
        ElseIf n >= 2 Then
            For i = 2 To n
                fibn = fibn2 + fibn1
                fibn2 = fibn1
                fibn1 = fibn
            Next i
            Return fibn
        End If
        Return 0
    End Function 'FiboBig

    Sub fibotest()
        Dim i As Integer, s As String
        i = 2000000  ' 2 millions
        s = FiboBig(i).ToString
        Console.WriteLine("fibo(" & i & ")=" & s & " - length=" & Len(s))
    End Sub 'fibotest


Imports System
Imports System.Collections.Generic
Imports BI = System.Numerics.BigInteger

Module Module1

    ' A sparse array of values calculated along the way
    Dim sl As SortedList(Of Integer, BI) = New SortedList(Of Integer, BI)()

    ' Square a BigInteger
    Function sqr(ByVal n As BI) As BI
        Return n * n
    End Function

    ' Helper routine for Fsl(). It adds an entry to the sorted list when necessary
    Sub IfNec(n As Integer)
        If Not sl.ContainsKey(n) Then sl.Add(n, Fsl(n))
    End Sub

    ' This routine is semi-recursive, but doesn't need to evaluate every number up to n.
    ' Algorithm from here: http://www.maths.surrey.ac.uk/hosted-sites/R.Knott/Fibonacci/fibFormula.html#section3
    Function Fsl(ByVal n As Integer) As BI
        If n < 2 Then Return n
        Dim n2 As Integer = n >> 1, pm As Integer = n2 + ((n And 1) << 1) - 1 : IfNec(n2) : IfNec(pm)
        Return If(n2 > pm, (2 * sl(pm) + sl(n2)) * sl(n2), sqr(sl(n2)) + sqr(sl(pm)))
    End Function

    ' Conventional iteration method (not used here)
    Function Fm(ByVal n As BI) As BI
        If n < 2 Then Return n
        Dim cur As BI = 0, pre As BI = 1
        For i As Integer = 0 To n - 1
            Dim sum As BI = cur + pre : pre = cur : cur = sum : Next : Return cur
    End Function

    Sub Main()
        Dim vlen As Integer, num As Integer = 2_000_000, digs As Integer = 35
        Dim sw As System.Diagnostics.Stopwatch = System.Diagnostics.Stopwatch.StartNew()
        Dim v As BI = Fsl(num) : sw.[Stop]()
        Console.Write("{0:n3} ms to calculate the {1:n0}th Fibonacci number, ", sw.Elapsed.TotalMilliseconds, num)
        vlen = CInt(Math.Ceiling(BI.Log10(v))) : Console.WriteLine("number of digits is {0}", vlen)
        If vlen < 10000 Then
            sw.Restart() : Console.WriteLine(v) : sw.[Stop]()
            Console.WriteLine("{0:n3} ms to write it to the console.", sw.Elapsed.TotalMilliseconds)
        Else
            Console.Write("partial: {0}...{1}", v / BI.Pow(10, vlen - digs), v Mod BI.Pow(10, digs))
        End If
    End Sub
End Module


Function fibo(n As Integer) As UInt64

  Dim noOne As UInt64 = 1
  Dim noTwo As UInt64 = 1	
  Dim sum As UInt64

  For i As Integer = 3 To n
      sum = noOne + noTwo
      noTwo = noOne
      noOne = sum
  Next

  Return noOne
End Function

sub fibonacci (n)
    n1 = 0
    n2 = 1
    for k = 1 to abs(n)
        sum = n1 + n2
        n1 = n2
        n2 = sum
    next k
    if n < 0 then
       return n1 * ((-1) ^ ((-n) + 1))
    else
       return n1
    end if
end sub

10 REM Only positive numbers
20 LET n=10
30 LET n1=0: LET n2=1
40 FOR k=1 TO n
50 LET sum=n1+n2
60 LET n1=n2
70 LET n2=sum
80 NEXT k
90 PRINT n1

10 DEF FN f(x)=INT (0.5+(((SQR 5+1)/2)^x)/SQR 5)