git.8kb.co.uk Git - playtime/mortgage_calculator/blob - mcalc.pl

   1 #!/usr/bin/perl
   2
   3 # Glyn Astill <glyn@8kb.co.uk> 11/10/2011
   4
   5 use strict;
   6 use Getopt::Long qw/GetOptions/;
   7 Getopt::Long::Configure('no_ignore_case');
   8
   9 my $debug = 0;
  10 my $USAGE = '-m <mortgage value> -a <arrangement fee> -i <interest rate>';
  11
  12 my $mortgage_value;
  13 my $arrangement_fee;
  14 my $interest_rate;
  15 my $interest_rate_term;
  16 my $monthly_payment;
  17 my $term;
  18 my $interest_rate_increase;
  19 my $cap_rate_increase;
  20 my $monthly_overpayment;
  21
  22 my $year;
  23 my $month;
  24
  25 my $total_mortgage;
  26 my $monthly_interest;
  27 my $month_value;
  28 my $total_paid;
  29 my $interest_accrued;
  30
  31 ##http://www.perl.com/doc/manual/html/lib/Getopt/Long.html
  32 use vars qw{%opt};
  33 die $USAGE unless
  34         GetOptions(\%opt,
  35                    'mortgage_value|m=n',
  36                    'arrangement_fee|a=n',
  37                    'interest_rate|i=f',
  38                    'interest_rate_term|it=n',
  39                    'term|t=n',
  40                    'interest_rate_increase|ii=f',
  41                    'cap_rate_increase|ic=f',
  42                    'monthly_overpayment|o=n',
  43                    'monthly_payment|p=n',
  44                    )
  45         and keys %opt
  46         and ! @ARGV;
  47
  48 ## initial call ... $ARGV[0] and $ARGV[1] are the command line arguments
  49
  50 $mortgage_value = $opt{mortgage_value};
  51 $arrangement_fee = ($opt{arrangement_fee} // 0);
  52 $interest_rate = ($opt{interest_rate} // 5);
  53 $interest_rate_term = ($opt{interest_rate_term} // 1);
  54 $monthly_payment = ($opt{monthly_payment} // 0);
  55 $term = ($opt{term} // 25);
  56 $interest_rate_increase = ($opt{interest_rate_increase} // 0);
  57 $cap_rate_increase = $opt{cap_rate_increase};
  58 $monthly_overpayment = ($opt{monthly_overpayment} // 0);
  59
  60 $total_mortgage = $mortgage_value+$arrangement_fee;
  61 $monthly_interest = ($interest_rate/100)/12;
  62
  63 $month_value = $total_mortgage;
  64 if (! $monthly_payment) {
  65         $monthly_payment = (($month_value*$monthly_interest)/(1-((1+$monthly_interest)**($term*12*-1))));
  66 }
  67
  68 print "\nMortgage value: ",$mortgage_value,"\n";
  69 print "Arrangement fee added on: ",$arrangement_fee, "\n";
  70 print "Term: ", $term, " year(s)\n";
  71 print "Interest rate: ",$interest_rate, "% (Monthly rate = ", $monthly_interest, "%)\n";
  72 print "Interest rate term: ",$interest_rate_term, " years\n";
  73 print "Initial monthly payment: ", sprintf("%.2f", $monthly_payment) ,"\n";
  74 print "After initial term rate jumps by: ",$interest_rate_increase,"%\n";
  75 print "Cap rate jumps at: ",$cap_rate_increase,"%\n" if ($cap_rate_increase);
  76 print "---------------------------------------\n";
  77 print "Total mortgage value: ",$total_mortgage,"\n";
  78 print "---------------------------------------\n\n";
  79
  80 do_it: {
  81         for ($year = 1; $year < $term; $year++) {
  82                 if ($year > $interest_rate_term) {
  83                         if ((! $cap_rate_increase) || ($interest_rate < $cap_rate_increase)) {
  84                                 $interest_rate = $interest_rate + $interest_rate_increase;
  85                                 if ($interest_rate < 0) {
  86                                         $interest_rate=0.0000000001;
  87                                 }
  88                                 elsif ($cap_rate_increase && ($interest_rate > $cap_rate_increase)) {
  89                                         $interest_rate = $cap_rate_increase;
  90                                 }
  91                                 $monthly_interest = ($interest_rate/100)/12;
  92                                 $monthly_payment = (($month_value*$monthly_interest)/(1-((1+$monthly_interest)**(($term-$year)*12*-1))));
  93                         }
  94                 }
  95
  96                 for ($month = 1; $month <= 12; $month++) {
  97                         $month_value = $month_value+($month_value*$monthly_interest)-($monthly_payment+$monthly_overpayment);
  98                         $total_paid = $total_paid + $monthly_payment;
  99                         $interest_accrued = $interest_accrued + ($month_value*$monthly_interest);
 100                         if (($month == 12) || ($month_value <= 0)){
 101                                 print "End of year ", pack("A5",$year);
 102                                 print "Mortgage: ", pack("A11",sprintf("%.2f", $month_value));
 103                                 print "Total paid: ", pack("A11", sprintf("%.2f", $total_paid));
 104                                 print "Total interest: ", pack("A11", sprintf("%.2f", $interest_accrued));
 105                                 print " (Rate ", $interest_rate, "%, Monthly Payment ", sprintf("%.2f", $monthly_payment);
 106
 107                                 if ($monthly_overpayment > 0) {
 108                                         print " Overpayment ", sprintf("%.2f", $monthly_overpayment);
 109                                 }
 110
 111                                 print ")\n";
 112
 113                                 if ($month_value <= 0) {
 114                                         print "Paid off in month ", $month, " of year ", $year, "\n";
 115                                         last do_it;
 116                                 }
 117
 118                         }
 119                 }
 120          }
 121  }
 122
 123 __END__