Free Pascal 2.0.4
Version of implementation Free Pascal of programming language PascalBugfix release.
Examples:
Factorial - Pascal (44):
This example uses recursive factorial definition.
Note that this example works in all given implementations of Pascal, but it produces slightly different results. In gpc everything works perfectly. Turbo Pascal and Free Pascal have arithmetic overflow for factorial of numbers greater than 12, but Free Pascal reports an error:
13! = Runtime error 215 at $004013C7
$004013C7
$00401449
$004063E0
while Turbo Pascal doesn’t detect the error and simply prints wrong values:
13! = 1932053504
14! = 1278945280
15! = 2004310016
16! = 2004189184
This example doesn’t work in Turbo Pascal 3.0 and earlier due to absence of longint
data type in these versions.
In GNU Pascal this program works without any problems.
program factorial;
function fact(n: integer): longint;
begin
if (n = 0) then
fact := 1
else
fact := n * fact(n - 1);
end;
var
n: integer;
begin
for n := 0 to 16 do
writeln(n, '! = ', fact(n));
end.
Hello, World! - Pascal (57):
program helloworld;
begin
writeln('Hello, World!');
end.
Fibonacci numbers - Pascal (58):
This example uses recursive definition of Fibonacci numbers.
program fibonacci;
function fib(n:integer): integer;
begin
if (n <= 2) then
fib := 1
else
fib := fib(n-1) + fib(n-2);
end;
var
i:integer;
begin
for i := 1 to 16 do
write(fib(i), ', ');
writeln('...');
end.
Factorial - Pascal (96):
This example is exactly the same as main recursive example for Pascal implementations, except for that it uses real
data type to store factorial values. Command writeln(f:-1:0)
outputs the floating point number f
with 0 digits after decimal point and left-justifies it.
program factorial;
function fact(n: integer): real;
begin
if (n = 0) then
fact := 1
else
fact := n * fact(n - 1);
end;
var
n: integer;
begin
for n := 0 to 16 do
writeln(n, '! = ', fact(n):-1:0);
end.
Quadratic equation - Pascal (178):
Pascal has built-in complex data type complex
, but using it is inconvenient in this case, because writeln
can’t output complex numbers directly, and functions Re
and Im
would have to be used. In this example calculations are done in real numbers. Library function halt
(added in Extended Pascal) exits current block (in later versions it is replaced with exit
).
program Quadratic;
var
A,B,C,D: integer;
begin
write('A = ');
readln(A);
if (A=0) then
begin
writeln('Not a quadratic equation.');
halt;
end;
write('B = ');
readln(B);
write('C = ');
readln(C);
D := B*B-4*A*C;
if (D=0) then
begin
writeln('x = ',-B/2.0/A);
halt;
end;
if (D>0) then
begin
writeln('x1 = ',(-B+Sqrt(D))/2.0/A);
writeln('x2 = ',(-B-Sqrt(D))/2.0/A);
end
else
begin
writeln('x1 = (',-B/2.0/A,',',Sqrt(-D)/2.0/A,')');
writeln('x2 = (',-B/2.0/A,',',-Sqrt(-D)/2.0/A,')');
end;
end.
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