Computer Programming II -10-

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1 Computer Programming II -10- Dr. Engin YILDIZTEPE Dr.Alper VAHAPLAR Random number routines Randomize procedure Random function Random (n) function RandomRange function RandomFrom function RandG function RandSeed variable 2 1

2 RandSeed variable RandSeed stores the built-in random number generator's seed. By assigning a specific value to RandSeed, you can use the Random function to repetitively generate a specific sequence of random numbers. This is useful for applications that deal with data statistics and simulations. 3 RandomFrom function Returns a randomly selected element from an array. We must add Math, StrUtils to the uses clause. The type of the array may can be double, integer or string. The result is the same type of the array. Use of: a:=randomfrom(arrayname); 4 2

3 RandomFrom Example 1 Write a program to take random samples from memo1 and add them into the listbox1. The user will give the sample size. Edit1 Button1 Memo1 ListBox1 5 ListBox Listbox1.items.Add : adds item to the listbox1 Listbox1.items[i] : access i. items. Listbox items contain the strings that appear in the list box. 6 3

4 RandomFrom example 1 We will use a dynamic string array. The user gives the sample size in the edit1. Program will take random samples from the string array. procedure TForm1.Button1Click(Sender: TObject); var dizi:array of string; i,n:integer; t:string; RandomFrom example 1 Writing strings from memo1 to the array: SetLength(dizi,Memo1.Lines.Count); for i:=0 to Memo1.Lines.Count-1 do dizi[i]:=memo1.lines[i] ;.. 8 4

5 Random from the array:.... ListBox1.Clear; n:=strtoint(edit1.text); Randomize; for i:=0 to n-1 do t:=randomfrom(dizi); ListBox1.Items.Add(t); RandomFrom example 1 9 RandomFrom example 1 procedure TForm1.BitBtn1Click(Sender: TObject); var dizi:array of string; i,n:integer; t:string; if ((Memo1.Lines.Count>0) and (Edit1.Text<>'')) then SetLength(dizi,Memo1.Lines.Count); for i:=0 to Memo1.Lines.Count-1 do dizi[i]:=memo1.lines[i]; ListBox1.Clear; n:=strtoint(edit1.text); Randomize; for i:=0 to n-1 do t:=randomfrom(dizi); ListBox1.Items.Add(t); Write same program for integer and double arrays. 10 5

6 RandG function Generates random numbers with Gaussian distribution. Delphi syntax: RandG(Mean, StdDev: Extended): Extended; ex: a:=randg(0,1) 11 RandG function example 2 Button1 Memo1 12 6

7 RandG function example 2 procedure TForm1.Button1Click(Sender: TObject); var m,st,d:extended; i,n:integer; if ((Edit1.Text<>'') and (Edit2.Text<>'') and (Edit3.Text<>'')) then Memo1.Clear; m:=strtofloat(edit1.text); st:=strtofloat(edit2.text); n:=strtoint(edit3.text); for i:=0 to n-1 do d:=randg(m,st); Memo1.Lines.Add(FormatFloat('#0.####0',d)); 13 Progress Bar Progress bars provide users with visual feedback about the progress of a procedure within an application. TProgressBar is in the Win32 page of the component palette. Properties: Min : Specifies the lower limit of the range of possible positions. Max: Specifies the upper limit of the range of possible positions. Position: Specifies the current position of the progress bar. Orientation : Specifies whether the progress bar is oriented vertically or horizontally. Smooth :Specifies whether the progress bar is smooth or segmented. Step :Specifies the amount that Position increases when the StepIt method is called. 14 7

RandG function example 3 Use a progress bar in previous example. 15 RandG function example 3 procedure TForm1.Button1Click(Sender: TObject); var m,st,d:extended; i,n:integer; if ((Edit1.

8 RandG function example 3 Use a progress bar in previous example. 15 RandG function example 3 procedure TForm1.Button1Click(Sender: TObject); var m,st,d:extended; i,n:integer; if ((Edit1.Text<>'') and (Edit2.Text<>'') and (Edit3.Text<>'')) then Memo1.Clear; m:=strtofloat(edit1.text); st:=strtofloat(edit2.text); n:=strtoint(edit3.text); ProgressBar1.Max:=n; for i:=0 to n-1 do d:=randg(m,st); Memo1.Lines.Add(FormatFloat('#0.####0',d)); ProgressBar1.Position:=i+1; 16 8

9 Gauge Is a control that can be used to graphically display the progress of a process It can be added from Samples page. The most representative properties of the gauge are: Kind :horizantal, vertical, needle, text or pie. MinValue:The minimum progress value MaxValue:The maximum progress value Progress: The current progress value BackColor : ForeColor : Step : 17 Gauge example 18 9

10 Gauge example Kind :gkpie Use ForeColor, BackColor gauge1.maxvalue gauge1.minvalue (defaults are 100 and 0) 19 RandG function Gauge procedure TForm1.Button1Click(Sender: TObject); var m,st,d:extended; i,n:integer; if ((Edit1.Text<>'') and (Edit2.Text<>'') and (Edit3.Text<>'')) then Memo1.Clear; m:=strtofloat(edit1.text); st:=strtofloat(edit2.text); n:=strtoint(edit3.text); Gauge1.MaxValue:=n; for i:=0 to n-1 do d:=randg(m,st); Memo1.Lines.Add(FormatFloat('#0.####0',d)); Gauge1.Progress:=i+1; 20 10

We are all familiar with the concept of a queue:

SEVENTEEN Queues We are all familiar with the concept of a queue: back of the queue next person joins front of the queue next person leaves Queues play an important role in computer systems, for example: