Mega Code Archive
[] Asal sayıları bulma
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//Asal Sayıları Bulmaya Yarayan Bir Program(Yazana teşekkürler)
program Primes;
{ function IsPrime
This function determines if a number is prime or not
Parameters:
x - the integer number to determine if prime or not
Return value (Boolean):
True if x is prime, else False
Preconditions/Postconditions:
None
}
function IsPrime( x: integer ) : Boolean;
var
factor : integer;
begin
if x < 2 then { No numbers < 2 are prime }
IsPrime := False
else if (x = 2) or (x = 3) then { 2 and 3 are prime }
IsPrime := True
else if not odd(x) then { other than 2, no even number is prime }
IsPrime := False
else begin { case: odd numbers > 3 }
{ look for an odd factor of x: if x has a factor, it must
be less than sqrt(x)
}
factor := 3;
while (sqr(factor) <= x) and ( x mod factor <> 0 ) do
factor := factor + 2; { try next odd number }
{ loop will stop whether x is prime or not (THIS is GOOD!)
afterward, must determine if it found a factor of x
}
IsPrime := x mod factor <> 0;
end
end;
{ procedure FindNextPrime
This procedure finds the next prime starting from an initial guess
Parameters:
InitialGuess - first guess for next prime
NextPrime - var parameter to store next prime in
Precondition:
InitialGuess is odd
Postconditions:
NextPrime holds the value of the next prime (and is odd)
}
procedure FindNextPrime( InitialGuess : integer; var NextPrime : integer );
var
Guess : integer;
begin
Guess := InitialGuess;
while not IsPrime( Guess ) do
Guess := Guess + 2;
NextPrime := Guess
end;
{ procedure FindPrimes
This procedure finds a series of prime numbers
Parameters:
NumOfPrimesToFind - the number of primes to find
Preconditions:
NumOfPrimesToFind is > 1
Postconditons:
None
}
procedure FindPrimes( NumOfPrimesToFind : integer );
var
Guess : integer;
PrimeNum : integer;
procedure PrintHeading; { nested procedure }
begin
writeln;
writeln(' Primes');
writeln('----------------')
end;
begin
PrintHeading;
writeln(1:5,' ', 2:7); { first prime (2) is a special case }
Guess := 3; { start with a odd number }
for PrimeNum := 2 to NumOfPrimesToFind do begin
FindNextPrime( Guess, Guess );
writeln(PrimeNum:5, ' ', Guess:7);
Guess := Guess + 2 { next odd number }
end
end;
{ procedure GetInput
This procedure gets the number of primes to find from user
Parameters:
NumOfPrimesToFind - var parameter to store number in
Preconditions:
None
Postcondtions:
NumOfPrimesToFind > 1
}
procedure GetInput( var NumOfPrimesToFind : integer );
begin
repeat
write('How many primes do you wish to find? ');
readln( NumOfPrimesToFind );
if NumOfPrimesToFind < 1 then
writeln('Must find at least 1 prime!')
until NumOfPrimesToFind >= 1;
end;
procedure PrintHeading;
begin
writeln(' Prime Finding Program');
writeln;
writeln(' This program finds prime numbers');
writeln
end;
{ main program }
var
NumOfPrimesToFind : integer;
begin
PrintHeading;
GetInput( NumOfPrimesToFind );
FindPrimes( NumOfPrimesToFind )
end.
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