RosettaCodeData/Task/Circular-primes/FreeBASIC/circular-primes.basic

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#define floor(x) ((x*2.0-0.5) Shr 1)
Function isPrime(Byval p As Integer) As Boolean
If p < 2 Then Return False
If p Mod 2 = 0 Then Return p = 2
If p Mod 3 = 0 Then Return p = 3
Dim As Integer d = 5
While d * d <= p
If p Mod d = 0 Then Return False Else d += 2
If p Mod d = 0 Then Return False Else d += 4
Wend
Return True
End Function
Function isCircularPrime(Byval p As Integer) As Boolean
Dim As Integer n = floor(Log(p)/Log(10))
Dim As Integer m = 10^n, q = p
For i As Integer = 0 To n
If (q < p Or Not isPrime(q)) Then Return false
q = (q Mod m) * 10 + floor(q / m)
Next i
Return true
End Function
Dim As Integer p = 2, dp = 1, cont = 0
Print("Primeros 19 primos circulares:")
While cont < 19
If isCircularPrime(p) Then Print p;" "; : cont += 1
p += dp: dp = 2
Wend
Sleep