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Math Functions: The Periodic Payments of a Loan

     

Introduction

While the InterestPayment() function calculates the amount paid as interest for a loan, the PeriodPayment() function calculates the actual amount that applies to the balance of the loan. This is referred to as the principal. Its syntax is:

Extended __fastcall PeriodPayment(const Extended Rate,
                                  int Period,
                                  int NPeriods,
                                  const Extended PresentValue,
                                  const Extended FutureValue,
                                  TPaymentTime PaymentTime);

Here is an example:

//---------------------------------------------------------------------------

#include <vcl.h>
#include <math.hpp>
#pragma hdrstop

#include "Exercise.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TfrmExercise *frmExercise;
//---------------------------------------------------------------------------
__fastcall TfrmExercise::TfrmExercise(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TfrmExercise::btnCalculateClick(TObject *Sender)
{
	Extended Present, Future, Rate, PPayment;
	int Periods, NPeriod;

	Present = StrToFloat(edtPresentValue->Text);
	Future = StrToFloat(edtFutureValue->Text);
	Rate = StrToFloat(edtInterestRate->Text) / 12;
	Periods = StrToInt(edtPeriods->Text);
	NPeriod = StrToInt(edtNPeriods->Text);

	// Apply the function
	PPayment = PeriodPayment(Rate / 100, Periods, NPeriod,
				 -Present,
				 Future,
				 ptStartOfPeriod);
	// Display the payment
	edtPeriodicPayment->Text = FloatToStrF(labs(PPayment), ffCurrency, 8, 2);
}
//---------------------------------------------------------------------------
void __fastcall TfrmExercise::btnCloseClick(TObject *Sender)
{
	PostQuitMessage(0);
}
//---------------------------------------------------------------------------
Periodic Payments
   

 

 
 
     
 

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