Additive primes: Difference between revisions
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return sum;
}</syntaxhighlight>
=={{header|Delphi}}==
{{works with|Delphi|6.0}}
{{libheader|SysUtils,StdCtrls}}
Many Rosette Code problems have similar operations. This problem was solved using subroutines that were written and used for other problems. Instead of packing all the operations in a single block of code, this example shows the advantage of breaking operations into separate modules that aids in code resuse.
<syntaxhighlight lang="Delphi">
{These routines would normally be in libraries but are shown here for clarity}
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;
procedure ShowDigitSumPrime(Memo: TMemo);
var N,Sum,Cnt: integer;
var NS,S: string;
begin
Cnt:=0;
S:='';
for N:=1 to 500-1 do
if IsPrime(N) then
begin
Sum:=SumDigits(N);
if IsPrime(Sum) then
begin
Inc(Cnt);
S:=S+Format('%6d',[N]);
if (Cnt mod 8)=0 then S:=S+CRLF;
end;
end;
Memo.Lines.Add(S);
Memo.Lines.Add('Count = '+IntToStr(Cnt));
end;
</syntaxhighlight>
{{out}}
<pre>
2 3 5 7 11 23 29 41
43 47 61 67 83 89 101 113
131 137 139 151 157 173 179 191
193 197 199 223 227 229 241 263
269 281 283 311 313 317 331 337
353 359 373 379 397 401 409 421
443 449 461 463 467 487
Count = 54
Elapsed Time: 2.812 ms.
</pre>
=={{header|Delphi}}==
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