Nice primes: Difference between revisions
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997</pre>
=={{header|Delphi}}==
{{works with|Delphi|6.0}}
{{libheader|SysUtils,StdCtrls}}
<syntaxhighlight lang="Delphi">
function IsPrime(N: int64): boolean;
{Fast, optimised prime test}
var I,Stop: int64;
begin
if (N = 2) or (N=3) then Result:=true
else if (n <= 1) or ((n mod 2) = 0) or ((n mod 3) = 0) then Result:= false
else
begin
I:=5;
Stop:=Trunc(sqrt(N+0.0));
Result:=False;
while I<=Stop do
begin
if ((N mod I) = 0) or ((N mod (I + 2)) = 0) then exit;
Inc(I,6);
end;
Result:=True;
end;
end;
function SumDigits(N: integer): integer;
{Sum the integers in a number}
var T: integer;
begin
Result:=0;
repeat
begin
T:=N mod 10;
N:=N div 10;
Result:=Result+T;
end
until N<1;
end;
function IsNiceNumber(N: integer): boolean;
{Return True if N is a nice number}
var Sum: integer;
begin
Result:=False;
{N must be primes}
if not IsPrime(N) then exit;
{Keep summing until one digit number}
Sum:=N;
repeat Sum:=SumDigits(Sum)
until Sum<10;
{Must be prime too}
Result:=IsPrime(Sum);
end;
procedure ShowNicePrimes(Memo: TMemo);
{Display Nice Primes between 501 and 999}
var I,Cnt: integer;
var S: string;
begin
Cnt:=0; S:='';
for I:=501 to 999 do
if IsNiceNumber(I) then
begin
S:=S+Format('%4d',[i]);
Inc(Cnt);
if (Cnt mod 5)=0 then S:=S+#$0D#$0A;
end;
Memo.Lines.Add(Format('Nice Primes: %3D',[Cnt]));
Memo.Lines.Add(S);
end;
</syntaxhighlight>
{{out}}
<pre>
Nice Primes: 33
509 547 563 569 587
599 601 617 619 641
653 659 673 677 691
709 727 743 761 797
821 839 853 857 887
907 911 929 941 947
977 983 997
</pre>
=={{header|C}}==
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