Additive primes: Difference between revisions

=={{header|Pascal}}==

{{works with|Free Pascal}}

<lang pascal>program AdditivePrimes;

{$IFDEF FPC}

{$MODE DELPHI}

{$ELSE}

{$APPTYPE CONSOLE}

{$ENDIF}

uses

sysutils;

type

tNum = array[0..15] of byte;

tNumSum = record

dgtNum,

dgtSum: tNum;

num : Uint32;

end;

tpNumSum = ^tNumSum;

function isPrime(n:Uint32):boolean;

var

p,flipflop: NativeUInt;

begin

if n< 63 then

EXIT(n in [2,3,5,7,11,13,17,19,23,29,

31,37,41,43,47, 53,59,61])

else

begin

IF (n AND 1=0) OR (n mod 3 = 0 ) then

EXIT(false);

result := true;

p := 5;

flipflop := 2;

while result do

Begin

result := n mod p <> 0;

p += flipflop;

flipflop := 6-flipflop;

if p*p>n then

BREAK;

end

end

end;

procedure IncNum(var NumSum: tNumSum;delta: Uint32);

const

BASE = 10;

var

r,

dg: UInt32;

le : Int32;

Begin

if delta = 0 then

EXIT;

NumSum.num +=delta;

le := 0;

repeat

r := delta div BASE;

delta -= BASE*r;

dg := NumSum.dgtNum[le]+delta;

IF dg >= BASE then

Begin

inc(r);

dg -= BASE;

end;

NumSum.dgtNum[le] := dg;

inc(le);

delta := r;

until r = 0;

//correct sum of digits // le is >= 1

delta := NumSum.dgtSum[le];

repeat

dec(le);

delta+= NumSum.dgtNum[le];

NumSum.dgtSum[le]:= delta;

until le = 0;

end;

const

RowWidth = 4;

NextRowCnt = 72 DIV RowWidth;

RANGE = 500;

MAX_OFFSET = 0;//1000*1000*1000;

var

NumSum: tNumSum;

i,cnt,delta,Nr: NativeUint;

BEGIN

Nr := NextRowCnt;

fillchar(NumSum,SizeOf(NumSum),#0);

cnt := 0;

delta := 0;

IncNum(NumSum,MAX_OFFSET);

For i := 1 to RANGE do

begin

inc(delta);

if isprime(i+MAX_OFFSET) then

Begin

IncNum(NumSum,delta);

delta := 0;

if isprime(NumSum.dgtSum[0]) then

begin

cnt +=1;

dec(nr);

write(NumSum.num:RowWidth);

if nr = 0 then

begin

writeln;

nr := NextRowCnt;

end;

end;

end;

end;

writeln(#10,cnt,' additive primes found.');

END.

</lang>

{{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

54 additive primes found.</pre>