Initial data commit

Task/Currency/Delphi/currency.delphi

@@ -0,0 +1,135 @@
+program Currency;
+
+{$APPTYPE CONSOLE}
+
+uses
+  System.SysUtils,
+  Velthuis.BigRationals,
+  Velthuis.BigDecimals,
+  Velthuis.BigIntegers;
+
+var
+  one: BigInteger;
+  hundred: BigInteger;
+  half: BigRational;
+
+type
+  TDc = record
+    value: BigInteger;
+    function ToString: string;
+    function Extend(n: BigInteger): TDc;
+    class operator Add(a, b: TDc): TDc;
+  end;
+
+  TTR = record
+    value: BigRational;
+    function SetString(const s: string; var TR: TTR): boolean;
+    function Tax(dc: TDc): TDc;
+  end;
+
+{ TDc }
+
+// Extend returns extended price of a unit price.
+class operator TDc.Add(a, b: TDc): TDc;
+begin
+  Result.value := a.value + b.value;
+end;
+
+function TDc.Extend(n: BigInteger): TDc;
+begin
+  Result.value := n * value;
+end;
+
+function TDc.ToString: string;
+var
+  d: BigInteger;
+begin
+  d := value.Divide(value, 100);
+  if value < 0 then
+    value := -value;
+  Result := Format('%s.%2s', [d.ToString, (value mod 100).ToString]);
+end;
+
+// ParseDC parses dollars and cents as a string into a DC.
+function ParseDC(s: string; var Dc: TDc): Boolean;
+var
+  r: BigRational;
+  d: BigDecimal;
+begin
+  Result := d.TryParse(s, d);
+  if not Result then
+  begin
+    Dc.value := 0;
+    exit(false);
+  end;
+
+  r := r.Create(d);
+  r := r.Multiply(r, 100);
+  if BigInteger.Compare(r.Denominator, 1) <> 0 then
+  begin
+    Dc.value := 0;
+    exit(false);
+  end;
+  Result := true;
+  Dc.value := r.Numerator;
+end;
+
+{ TTR }
+
+function TTR.SetString(const s: string; var TR: TTR): boolean;
+var
+  d: BigDecimal;
+begin
+
+  Result := d.TryParse(s, d);
+  if Result then
+    TR.value := BigRational.Create(d);
+end;
+
+function TTR.Tax(dc: TDc): TDc;
+var
+  r: BigRational;
+  i: BigInteger;
+begin
+  r := BigRational.Create(dc.value, 1);
+  r := r.Multiply(r, self.value);
+  r := r.add(r, half);
+  i := i.Divide(r.Numerator, r.Denominator);
+  Result.value := i;
+end;
+
+var
+  hamburgerPrice, milkshakePrice, totalBeforeTax, tax, total: TDc;
+  taxRate: TTR;
+
+begin
+  one := 1;
+  hundred := 100;
+  half := BigRational.Create(1, 2);
+
+  if not ParseDC('5.50', hamburgerPrice) then
+  begin
+    Writeln('Invalid hamburger price');
+    halt(1);
+  end;
+
+  if not ParseDC('2.86', milkshakePrice) then
+  begin
+    Writeln('Invalid milkshake price');
+    halt(2);
+  end;
+
+  if not taxRate.SetString('0.0765', taxRate) then
+  begin
+    Writeln('Invalid tax rat');
+    halt(3);
+  end;
+
+  totalBeforeTax := hamburgerPrice.Extend(4000000000000000) + milkshakePrice.Extend(2);
+  tax := taxRate.Tax(totalBeforeTax);
+  total := totalBeforeTax + tax;
+  Writeln('Total before tax: ', totalBeforeTax.ToString: 22);
+  Writeln('             Tax: ', tax.ToString: 22);
+  Writeln('           Total: ', total.ToString: 22);
+  readln;
+end.