Long multiplication: Difference between revisions
Added Delphi example
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<lang Dc>2 64^ 2 64^ *p</lang>
{{incorrect|Dc|A Dc solution might be: Represent bignums as numerical strings and implement arithmetic functions on them.}}
=={{header|Delphi}}==
{{libheader| System.SysUtils}}
{{Trans|Go}}
Copy of core Go answer.
<lang Delphi>
program Long_multiplication;
{$APPTYPE CONSOLE}
uses
System.SysUtils;
type
TLongMul = record
private
function Add(x, y: TArray<byte>): TArray<byte>;
function ByteToString(b: TArray<byte>): Ansistring;
function d(b: byte): Byte;
function mulDigit(x: TArray<byte>; y: byte): TArray<byte>;
function mul(x1, y1: AnsiString): AnsiString;
public
value: string;
class operator Multiply(a, b: TLongMul): TLongMul;
class operator Implicit(a: TLongMul): string;
class operator Implicit(a: string): TLongMul;
end;
function TLongMul.d(b: byte): Byte;
begin
if (b < ord('0')) or (b > ord('9')) then
raise Exception.Create('digit 0-9 expected: ' + ord(b).ToString);
Result := ord(b) - ord('0');
end;
class operator TLongMul.Implicit(a: string): TLongMul;
begin
Result.value := a;
end;
class operator TLongMul.Implicit(a: TLongMul): string;
begin
Result := a.value;
end;
function TLongMul.Add(x, y: TArray<byte>): TArray<byte>;
begin
if length(x) < Length(y) then
begin
var tmp := y;
y := x;
x := tmp;
end;
var b: TArray<byte>;
SetLength(b, length(x) + 1);
var c: byte := 0;
for var i := 1 to Length(x) do
begin
if i <= Length(y) then
c := c + d(y[Length(y) - i]);
var s := d(x[Length(x) - i]) + c;
c := s div 10;
b[length(b) - i] := (s mod 10) + ord('0');
end;
if c = 0 then
begin
Result := b;
Delete(Result, 0, 1);
exit;
end;
b[0] := c + ord('0');
Result := b;
end;
function TLongMul.mulDigit(x: TArray<byte>; y: byte): TArray<byte>;
begin
if y = ord('0') then
begin
SetLength(result, 1);
Result[0] := y;
exit
end;
y := d(y);
var b: TArray<byte>;
SetLength(b, length(x) + 1);
var c: byte := 0;
for var i := 1 to Length(x) do
begin
var s := d(x[Length(x) - i]) * y + c;
c := s div 10;
b[length(b) - i] := (s mod 10) + ord('0');
end;
if c = 0 then
begin
Result := b;
Delete(Result, 0, 1);
exit;
end;
b[0] := c + ord('0');
Result := b;
end;
class operator TLongMul.Multiply(a, b: TLongMul): TLongMul;
begin
Result.value := a.mul(a, b);
end;
function TLongMul.ByteToString(b: TArray<byte>): Ansistring;
begin
SetLength(Result, length(b));
move(b[0], Result[1], length(b));
end;
function TLongMul.mul(x1, y1: AnsiString): AnsiString;
var
x, y: TArray<byte>;
res: TArray<byte>;
begin
SetLength(x, length(x1));
move(x1[1], x[0], length(x1));
SetLength(y, length(y1));
move(y1[1], y[0], length(y1));
res := mulDigit(x, y[length(y) - 1]);
var zeros: TArray<byte> := [];
for var i := 2 to Length(y) do
begin
SetLength(zeros, Length(zeros) + 1);
zeros[High(zeros)] := ord('0');
res := add(res, Concat(mulDigit(x, y[Length(y) - i]), zeros));
end;
Result := ByteToString(res);
end;
const
validate = '340282366920938463463374607431768211456';
var
num: TLongMul;
begin
num.value := '18446744073709551616';
Writeln((num * num).value);
Writeln(validate);
Readln;
end.</lang>
{{out}}
<pre>340282366920938463463374607431768211456
340282366920938463463374607431768211456</pre>
=={{header|EchoLisp}}==
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