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git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@7882 8e941d3f-bd1b-0410-a28a-d453659cc2b4
126 lines
3.1 KiB
ObjectPascal
126 lines
3.1 KiB
ObjectPascal
unit DblDeclineUnit;
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{$mode objfpc}{$H+}
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interface
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uses
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Classes, SysUtils, FileUtil, LResources, Forms, Controls, Graphics, Dialogs,
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StdCtrls, Math, contexthelpunit;
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type
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{ TDblDeclineFrm }
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TDblDeclineFrm = class(TForm)
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HelpBtn: TButton;
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ResetBtn: TButton;
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ComputeBtn: TButton;
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ReturnBtn: TButton;
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CostEdit: TEdit;
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LifeEdit: TEdit;
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EndEdit: TEdit;
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PeriodEdit: TEdit;
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DeprecEdit: TEdit;
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Label1: TLabel;
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Label2: TLabel;
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Label3: TLabel;
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Label4: TLabel;
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Label5: TLabel;
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procedure ComputeBtnClick(Sender: TObject);
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procedure FormShow(Sender: TObject);
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procedure HelpBtnClick(Sender: TObject);
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procedure ResetBtnClick(Sender: TObject);
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function DoubleDecliningBalance(Cost, Salvage: Extended; Life, Period: Integer): Extended;
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private
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{ private declarations }
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public
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{ public declarations }
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end;
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var
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DblDeclineFrm: TDblDeclineFrm;
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implementation
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{ TDblDeclineFrm }
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procedure TDblDeclineFrm.ResetBtnClick(Sender: TObject);
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begin
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CostEdit.Text := '';
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LifeEdit.Text := '';
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EndEdit.Text := '';
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PeriodEdit.Text := '';
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DeprecEdit.Text := '';
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end;
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procedure TDblDeclineFrm.FormShow(Sender: TObject);
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begin
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ResetBtnClick(self);
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end;
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procedure TDblDeclineFrm.HelpBtnClick(Sender: TObject);
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begin
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ContextHelpForm.HelpMessage((Sender as TButton).tag);
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end;
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procedure TDblDeclineFrm.ComputeBtnClick(Sender: TObject);
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VAR
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Depreciation, Cost, Salvage : Extended;
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Life, Period : integer;
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begin
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Cost := StrToFloat(CostEdit.Text);
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Salvage := StrToFloat(EndEdit.Text);
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Life := StrToInt(LifeEdit.Text);
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Period := StrToInt(PeriodEdit.Text);
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Depreciation := DoubleDecliningBalance(Cost, Salvage, Life, Period);
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DeprecEdit.Text := FloatToStr(Depreciation);
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end;
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function TDblDeclineFrm.DoubleDecliningBalance(Cost, Salvage: Extended; Life, Period: Integer): Extended;
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{ dv := cost * (1 - 2/life)**(period - 1)
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DDB = (2/life) * dv
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if DDB > dv - salvage then DDB := dv - salvage
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if DDB < 0 then DDB := 0
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}
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var
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DepreciatedVal, Factor: Extended;
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begin
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Result := 0;
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if (Period < 1) or (Life < Period) or (Life < 1) or (Cost <= Salvage) then
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Exit;
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{depreciate everything in period 1 if life is only one or two periods}
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if ( Life <= 2 ) then
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begin
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if ( Period = 1 ) then
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DoubleDecliningBalance:=Cost-Salvage
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else
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DoubleDecliningBalance:=0; {all depreciation occurred in first period}
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exit;
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end;
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Factor := 2.0 / Life;
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DepreciatedVal := Cost * IntPower((1.0 - Factor), Period - 1);
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{DepreciatedVal is Cost-(sum of previous depreciation results)}
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Result := Factor * DepreciatedVal;
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{Nominal computed depreciation for this period. The rest of the
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function applies limits to this nominal value. }
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{Only depreciate until total depreciation equals cost-salvage.}
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if Result > DepreciatedVal - Salvage then
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Result := DepreciatedVal - Salvage;
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{No more depreciation after salvage value is reached. This is mostly a nit.
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If Result is negative at this point, it's very close to zero.}
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if Result < 0.0 then
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Result := 0.0;
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end;
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initialization
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{$I dbldeclineunit.lrs}
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end.
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