Truncatable primes: Difference between revisions
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>./ step&digits^:5 seed NB. right truncatable
739399</lang>
=={{header|PureBasic}}==
<lang PureBasic>#MaxLim = 999999
Procedure is_Prime(n)
If n<=1 : ProcedureReturn #False
ElseIf n<4 : ProcedureReturn #True
ElseIf n%2=0: ProcedureReturn #False
ElseIf n<9 : ProcedureReturn #True
ElseIf n%3=0: ProcedureReturn #False
Else
Protected r=Round(Sqr(n),#PB_Round_Down)
Protected f=5
While f<=r
If n%f=0 Or n%(f+2)=0
ProcedureReturn #False
EndIf
f+6
Wend
EndIf
ProcedureReturn #True
EndProcedure
Procedure TruncateLeft(n)
Protected s.s=Str(n), l=Len(s)-1
If Not FindString(s,"0",1)
While l>0
s=Right(s,l)
If Not is_Prime(Val(s))
ProcedureReturn #False
EndIf
l-1
Wend
ProcedureReturn #True
EndIf
EndProcedure
Procedure TruncateRight(a)
Repeat
a/10
If Not a
Break
ElseIf Not is_Prime(a) Or a%10=0
ProcedureReturn #False
EndIf
ForEver
ProcedureReturn #True
EndProcedure
i=#MaxLim
Repeat
If is_Prime(i)
If Not truncateleft And TruncateLeft(i)
truncateleft=i
EndIf
If Not truncateright And TruncateRight(i)
truncateright=i
EndIf
EndIf
If truncateleft And truncateright
Break
Else
i-2
EndIf
Until i<=0
x.s="Largest TruncateLeft= "+Str(truncateleft)
y.s="Largest TruncateRight= "+Str(truncateright)
MessageRequester("Truncatable primes",x+#CRLF$+y)</lang>
== {{header|Python}} ==
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