fpspreadsheet: Add financial function PV and PMT to test_formula_func demo.

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@3285 8e941d3f-bd1b-0410-a28a-d453659cc2b4

components/fpspreadsheet/examples/other/test_formula_func.lpi

@@ -52,6 +52,7 @@
     <RunParams>
       <local>
         <FormatVersion Value="1"/>
+        <LaunchingApplication PathPlusParams="\usr\X11R6\bin\xterm -T 'Lazarus Run Output' -e $(LazarusDir)\tools\runwait.sh $(TargetCmdLine)"/>
       </local>
     </RunParams>
     <RequiredPackages Count="1">
@@ -80,11 +81,6 @@
       <Debugging>
         <DebugInfoType Value="dsDwarf2Set"/>
       </Debugging>
-      <Options>
-        <Win32>
-          <GraphicApplication Value="True"/>
-        </Win32>
-      </Options>
     </Linking>
   </CompilerOptions>
   <Debugging>

components/fpspreadsheet/examples/other/test_formula_func.lps

@@ -4,165 +4,194 @@
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+        <UnitName Value="fpolebasic"/>
+        <EditorIndex Value="1"/>
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+        <CursorPos X="29" Y="53"/>
+        <UsageCount Value="13"/>
+        <Loaded Value="True"/>
+      </Unit4>
+      <Unit5>
+        <Filename Value="..\..\xlsbiff8.pas"/>
+        <UnitName Value="xlsbiff8"/>
+        <EditorIndex Value="5"/>
+        <TopLine Value="63"/>
+        <CursorPos X="20" Y="83"/>
+        <UsageCount Value="12"/>
+        <Loaded Value="True"/>
+      </Unit5>
+      <Unit6>
+        <Filename Value="..\..\xlscommon.pas"/>
+        <UnitName Value="xlscommon"/>
+        <EditorIndex Value="6"/>
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components/fpspreadsheet/examples/other/test_formula_func.pas

@@ -1,18 +1,34 @@
-{ This demo show how a user-provided function can be used for calculation of
+{ This demo show how user-provided functions can be used for calculation of
   rpn formulas that are built-in to fpspreadsheet, but don't have an own
-  calculation procedure. }
+  calculation procedure.
+
+  The example will show implementation of the some financial formulas:
+  - FV(...)  (future value)
+  - PV(...)  (present value)
+  - PMT(...) (payment)
+
+  The demo writes an xls file which uses these formulas and then displays
+  the result in a console window. (Open the generated file in Excel or
+  Open/LibreOffice and compare).
+}
 
 program test_formula_func;
 
-{$mode objfpc}{$H+}
+//{$mode objfpc}{$H+}
+{$mode delphi}{$H+}
 
 uses
-  {$IFDEF UNIX}{$IFDEF UseCThreads}
+ {$IFDEF UNIX}{$IFDEF UseCThreads}
   cthreads,
   {$ENDIF}{$ENDIF}
-  Classes, laz_fpspreadsheet
+  Classes, SysUtils, laz_fpspreadsheet
   { you can add units after this },
-  math, fpspreadsheet, fpsfunc;
+  math, fpspreadsheet, xlsbiff8, fpsfunc;
+
+
+{------------------------------------------------------------------------------}
+{           Basic implmentation of the three financial funtions                }
+{------------------------------------------------------------------------------}
 
 const
   paymentAtEnd = 0;
@@ -24,24 +40,72 @@ const
   - "number_periods" is the number of payment periods, i.e. number of payments
     for the annuity.
   - "payment" is the amount of the payment made each period
-  - "PV" is the present value of the payments.
+  - "pv" is the present value of the payments.
   - "payment_type" indicates when the payments are due (see paymentAtXXX constants)
-  see: http://en.wikipedia.org/wiki/Future_value
+  see: http://en.wikipedia.org/wiki/Time_value_of_money
+
+  In Excel's implementation the payments and the FV add up to 0:
+      FV + PV q^n + PMT (q^n - 1) / (q - 1) = 0
 }
-function FV(interest_rate, number_periods, payment, pv: Double;
+function FV(interest_rate: Double; number_periods: Integer; payment, pv: Double;
   payment_type: integer): Double;
 var
-  q: Double;
+  q, qn, factor: Double;
 begin
   q := 1.0 + interest_rate;
-
-  Result := pv * power(q, number_periods) +
-            (power(q, number_periods) - 1) / (q - 1) * payment;
-
+  qn := power(q, number_periods);
+  factor := (qn - 1) / (q - 1);
   if payment_type = paymentAtBegin then
-    Result := Result * q;
+    factor := factor * q;
+
+  Result := -(pv * qn + payment*factor);
 end;
 
+{ Calculates the regular payments for a loan based on an interest rate and a
+  constant payment schedule
+  Arguments as shown for FV(), in addition:
+  - "fv" is the future value of the payments.
+  see: http://en.wikipedia.org/wiki/Time_value_of_money
+  }
+function PMT(interest_rate: Double; number_periods: Integer; pv, fv: Double;
+  payment_type: Integer): Double;
+var
+  q, qn, factor: Double;
+begin
+  q := 1.0 + interest_rate;
+  qn := power(q, number_periods);
+  factor := (qn - 1) / (q - 1);
+  if payment_type = paymentAtBegin then
+    factor := factor * q;
+
+  Result := -(fv + pv * qn) / factor;
+end;
+
+{ Calculates the present value of an investment based on an interest rate and
+  a constant payment schedule.
+  Arguments as shown for FV(), in addition:
+  - "fv" is the future value of the payments.
+  see: http://en.wikipedia.org/wiki/Time_value_of_money
+}
+function PV(interest_rate: Double; number_periods: Integer; payment, fv: Double;
+  payment_type: Integer): Double;
+var
+  q, qn, factor: Double;
+begin
+  q := 1.0 + interest_rate;
+  qn := power(q, number_periods);
+  factor := (qn - 1) / (q - 1);
+  if payment_type = paymentAtBegin then
+    factor := factor * q;
+
+  Result := -(fv + payment*factor) / qn;
+end;
+
+
+{------------------------------------------------------------------------------}
+{                    Adaption for usage by fpspreadsheet                       }
+{------------------------------------------------------------------------------}
+
 function fpsFV(Args: TsArgumentStack; NumArgs: Integer): TsArgument;
 var
   data: TsArgNumberArray;
@@ -52,14 +116,47 @@ begin
   if Args.PopNumberValues(NumArgs, false, data, Result) then
     // Call our FV function with the NumberValues of the arguments.
     Result := CreateNumberArg(FV(
-      data[0],       // interest rate
-      data[1],       // number of payments
-      data[2],       // payment
-      data[3],       // present value
-      round(data[4]) // payment type
+      data[0],         // interest rate
+      round(data[1]),  // number of payments
+      data[2],         // payment
+      data[3],         // present value
+      round(data[4])   // payment type
     ));
 end;
 
+function fpsPMT(Args: TsArgumentStack; NumArgs: Integer): TsArgument;
+var
+  data: TsArgNumberArray;
+begin
+  if Args.PopNumberValues(NumArgs, false, data, Result) then
+    Result := CreateNumberArg(PMT(
+      data[0],         // interest rate
+      round(data[1]),  // number of payments
+      data[2],         // present value
+      data[3],         // future value
+      round(data[4])   // payment type
+    ));
+end;
+
+function fpsPV(Args: TsArgumentStack; NumArgs: Integer): TsArgument;
+var
+  data: TsArgNumberArray;
+begin
+  if Args.PopNumberValues(NumArgs, false, data, Result) then
+    Result := CreateNumberArg(PV(
+      data[0],         // interest rate
+      round(data[1]),  // number of payments
+      data[2],         // payment
+      data[3],         // future value
+      round(data[4])   // payment type
+    ));
+end;
+
+
+{------------------------------------------------------------------------------}
+{        Write xls file comparing our own calculations with Excel result       }
+{------------------------------------------------------------------------------}
+procedure WriteFile(AFileName: String);
 const
   INTEREST_RATE = 0.03;
   NUMBER_PAYMENTS = 10;
@@ -70,54 +167,171 @@ const
 var
   workbook: TsWorkbook;
   worksheet: TsWorksheet;
+  fval, pval, pmtval: Double;
 
 begin
+  { We have to register our financial function in fpspreadsheet. Otherwise an
+    error code would be displayed in the reading part of this demo in these
+    formula cells. }
   RegisterFormulaFunc(fekFV, @fpsFV);
+  RegisterFormulaFunc(fekPMT, @fpsPMT);
+  RegisterFormulaFunc(fekPV, @fpsPV);
 
   workbook := TsWorkbook.Create;
   try
     worksheet := workbook.AddWorksheet('Financial');
     worksheet.Options := worksheet.Options + [soCalcBeforeSaving];
-    worksheet.WriteColWidth(0, 20);
+    worksheet.WriteColWidth(0, 40);
 
     worksheet.WriteUTF8Text(0, 0, 'Interest rate');
-    worksheet.WriteNumber(0, 1, INTEREST_RATE, nfPercentage, 1);
+    worksheet.WriteNumber(0, 1, INTEREST_RATE, nfPercentage, 1);        // B1
 
     worksheet.WriteUTF8Text(1, 0, 'Number of payments');
-    worksheet.WriteNumber(1, 1, NUMBER_PAYMENTS);
+    worksheet.WriteNumber(1, 1, NUMBER_PAYMENTS);                       // B2
 
     worksheet.WriteUTF8Text(2, 0, 'Payment');
-    worksheet.WriteCurrency(2, 1, PAYMENT, nfCurrency, 2, '$');
+    worksheet.WriteCurrency(2, 1, PAYMENT, nfCurrency, 2, '$');         // B3
 
     worksheet.WriteUTF8Text(3, 0, 'Present value');
-    worksheet.WriteCurrency(3, 1, PRESENT_VALUE, nfCurrency, 2, '$');
+    worksheet.WriteCurrency(3, 1, PRESENT_VALUE, nfCurrency, 2, '$');   // B4
 
-    worksheet.WriteUTF8Text(4, 0, 'Payment at end');
-    worksheet.WriteBoolValue(4, 1, PAYMENT_WHEN = paymentAtEnd);
+    worksheet.WriteUTF8Text(4, 0, 'Payment at end (0) or at begin (1)');
+    worksheet.WriteNumber(4, 1, PAYMENT_WHEN);                          // B5
 
+    // future value calculation
+    fval := FV(INTEREST_RATE, NUMBER_PAYMENTS, PAYMENT, PRESENT_VALUE, PAYMENT_WHEN);
     worksheet.WriteUTF8Text(6, 0, 'Future value');
     worksheet.WriteFontStyle(6, 0, [fssBold]);
     worksheet.WriteUTF8Text(7, 0, 'Our calculation');
-    worksheet.WriteCurrency(7, 1,
-      FV(INTEREST_RATE, NUMBER_PAYMENTS, PAYMENT, PRESENT_VALUE, PAYMENT_WHEN),
-      nfCurrency, 2, '$'
-    );
+    worksheet.WriteCurrency(7, 1, fval, nfCurrency, 2, '$');
 
-    worksheet.WriteUTF8Text(8, 0, 'Excel''s calculation');
+    worksheet.WriteUTF8Text(8, 0, 'Excel''s calculation using constants');
     worksheet.WriteNumberFormat(8, 1, nfCurrency, 2, '$');
-    worksheet.WriteRPNFormula(8, 1, CreateRPNFormula(
+    worksheet.WriteRPNFormula(8, 1, CreateRPNFormula(                  // B9
       RPNNumber(INTEREST_RATE,
       RPNNumber(NUMBER_PAYMENTS,
-      RPNNumber(-PAYMENT,
-      RPNNumber(-PRESENT_VALUE,
+      RPNNumber(PAYMENT,
+      RPNNumber(PRESENT_VALUE,
       RPNNumber(PAYMENT_WHEN,
       RPNFunc(fekFV, 5,
       nil))))))));
+    worksheet.WriteUTF8Text(9, 0, 'Excel''s calculation using cell values');
+    worksheet.WriteNumberFormat(9, 1, nfCurrency, 2, '$');
+    worksheet.WriteRPNFormula(9, 1, CreateRPNFormula(                  // B9
+      RPNCellValue('B1',   // interest rate
+      RPNCellValue('B2',   // number of periods
+      RPNCellValue('B3',   // payment
+      RPNCellValue('B4',   // present value
+      RPNCellValue('B5',   // payment at end or at start
+      RPNFunc(fekFV, 5,    // Call Excel's FV formula
+      nil))))))));
 
-    workbook.WriteToFile('test_fv.xls', sfExcel8, true);
+    // present value calculation
+    pval := PV(INTEREST_RATE, NUMBER_PAYMENTS, PAYMENT, fval, PAYMENT_WHEN);
+    worksheet.WriteUTF8Text(11, 0, 'Present value');
+    worksheet.WriteFontStyle(11, 0, [fssBold]);
+    worksheet.WriteUTF8Text(12, 0, 'Our calculation');
+    worksheet.WriteCurrency(12, 1, pval, nfCurrency, 2, '$');
+
+    worksheet.WriteUTF8Text(13, 0, 'Excel''s calculation using constants');
+    worksheet.WriteNumberFormat(13, 1, nfCurrency, 2, '$');
+    worksheet.WriteRPNFormula(13, 1, CreateRPNFormula(
+      RPNNumber(INTEREST_RATE,
+      RPNNumber(NUMBER_PAYMENTS,
+      RPNNumber(PAYMENT,
+      RPNNumber(fval,
+      RPNNumber(PAYMENT_WHEN,
+      RPNFunc(fekPV, 5,
+      nil))))))));
+    Worksheet.WriteUTF8Text(14, 0, 'Excel''s calculation using cell values');
+    worksheet.WriteNumberFormat(14, 1, nfCurrency, 2, '$');
+    worksheet.WriteRPNFormula(14, 1, CreateRPNFormula(
+      RPNCellValue('B1',   // interest rate
+      RPNCellValue('B2',   // number of periods
+      RPNCellValue('B3',   // payment
+      RPNCellValue('B10',  // future value
+      RPNCellValue('B5',   // payment at end or at start
+      RPNFunc(fekPV, 5,    // Call Excel's PV formula
+      nil))))))));
+
+    // payments calculation
+    pmtval := PMT(INTEREST_RATE, NUMBER_PAYMENTS, PRESENT_VALUE, fval, PAYMENT_WHEN);
+    worksheet.WriteUTF8Text(16, 0, 'Payment');
+    worksheet.WriteFontStyle(16, 0, [fssBold]);
+    worksheet.WriteUTF8Text(17, 0, 'Our calculation');
+    worksheet.WriteCurrency(17, 1, pmtval, nfCurrency, 2, '$');
+
+    worksheet.WriteUTF8Text(18, 0, 'Excel''s calculation using constants');
+    worksheet.WriteNumberFormat(18, 1, nfCurrency, 2, '$');
+    worksheet.WriteRPNFormula(18, 1, CreateRPNFormula(
+      RPNNumber(INTEREST_RATE,
+      RPNNumber(NUMBER_PAYMENTS,
+      RPNNumber(PRESENT_VALUE,
+      RPNNumber(fval,
+      RPNNumber(PAYMENT_WHEN,
+      RPNFunc(fekPMT, 5,
+      nil))))))));
+    Worksheet.WriteUTF8Text(19, 0, 'Excel''s calculation using cell values');
+    worksheet.WriteNumberFormat(19, 1, nfCurrency, 2, '$');
+    worksheet.WriteRPNFormula(19, 1, CreateRPNFormula(
+      RPNCellValue('B1',   // interest rate
+      RPNCellValue('B2',   // number of periods
+      RPNCellValue('B4',   // present value
+      RPNCellValue('B10',  // future value
+      RPNCellValue('B5',   // payment at end or at start
+      RPNFunc(fekPMT, 5,   // Call Excel's PMT formula
+      nil))))))));
+
+    workbook.WriteToFile(AFileName, sfExcel8, true);
 
   finally
     workbook.Free;
   end;
+end;
+
+{------------------------------------------------------------------------------}
+{                  Read xls file to display Excel's results                    }
+{------------------------------------------------------------------------------}
+procedure ReadFile(AFileName: String);
+var
+  workbook: TsWorkbook;
+  worksheet: TsWorksheet;
+  r: Cardinal;
+  s1, s2: String;
+begin
+  workbook := TsWorkbook.Create;
+  try
+    workbook.ReadFormulas := true;
+    workbook.ReadFromFile(AFilename, sfExcel8);
+
+    worksheet := workbook.GetFirstWorksheet;
+
+    // Write all cells with contents to the console
+    WriteLn('');
+    WriteLn('Contents of the first worksheet of the file:');
+    WriteLn('');
+
+    for r := 0 to worksheet.GetLastRowIndex do begin
+      s1 := UTF8ToAnsi(worksheet.ReadAsUTF8Text(r, 0));
+      s2 := UTF8ToAnsi(worksheet.ReadAsUTF8Text(r, 1));
+      if s1 = '' then
+        WriteLn
+      else
+        WriteLn(s1+': ':50, s2);
+    end;
+
+    WriteLn;
+    WriteLn('Press [ENTER] to close...');
+    ReadLn;
+  finally
+    workbook.Free;
+  end;
+end;
+
+
+begin
+  WriteFile('test_fv.xls');
+  ReadFile('test_fv.xls');
 end.
 
+