Use of "bit" in Delphi (2)-Set

Each element in the Set occupies only one binary bit. A set of less than eight elements only needs one byte.
First observe the size of the Set:

 
Type tset1 = set of (A1, A2, A3, A4, A5, A6, A7, A8); {exactly corresponds to eight bytes} tset2 = set of (B1, b2, B3); {only three digits in one byte need to occupy one byte} tset3 = set of (C1, C2, C3, C4, C5, C6, C7, C8, c9); {9 digits are required, and one byte cannot accommodate} tset4 = set of char; Procedure tform1.button1click (Sender: tobject); begin showmessagefmt ('% d, % d', [sizeof (tset1), // 1 sizeof (tset2), // 1 sizeof (tset3), // 2 sizeof (tset4) // 32]); end;

  
 

Binary representation of the insight set:

{View binary functions} function Tobin (P: pbytearray; B: integer): string; var I, j: integer; begin result: = stringofchar ('0 ', B * 8); for I: = 0 to B-1 do for J: = 0 to 7 do if odd (P ^ [b-1-i] SHR J) then result [I * 8 + 8-J]: = '1'; end; Procedure tform1.button1click (Sender: tobject); var set1: Set of (a, B, c, d, e, f, g, h); begin set1: = []; showmessage (Tobin (@ set1, sizeof (set1); // 00000000 set1: = [a, B, c, d, e, f, g, h]; showmessage (Tobin (@ set1, sizeof (set1); // 11111111 set1: = [a, B, c]; showmessage (Tobin (@ set1, sizeof (set1); // 00000111 set1: = [A, B, C, H]; showmessage (Tobin (@ set1, sizeof (set1); // returns 111end;

  
 

You can even think of a set as a number:

Procedure tform1.button1click (Sender: tobject); Type tset = set of (a, B, c, d, e, f, g, h); var S1, S2, S3, S4: tset; begin S1: = []; S2: = [a, B, c, d, e, f, g, h]; S3: = [a, B, c]; S4: = [A, B, C, H]; showmessage (inttostr (byte (S1 ))); // 0 showmessage (inttostr (byte (S2); // 255 showmessage (inttostr (byte (S3 ))); // 7 showmessage (inttostr (byte (S4); // 135end;

  
 

Redo the previous example in the form of a set (the form design and test results are the same as before ):

VaR set1: Set of 0 .. 7; {prepare to store the following eight States with a custom set variable set1} procedure tform1.formcreate (Sender: tobject); begin checklistbox1.items. commatext: = 'a, B, c, d, e, f, g, H'; button1.caption: = 'Save status'; button2.caption: = 'Restore status'; button3.caption: = 'all select'; button4.caption: = 'all deselected '; button1.tag: = 1; button2.tag: = 2; button3.tag: = 3; button4.tag: = 4; button2.onclick: = button1.onclick; button3.onclick: = button1.onclick; button4.onclick: = button1.onclick; end; Procedure tform1.button1click (Sender: tobject); var I: integer; begin if tbutton (sender ). tag = 1 then set1: = []; for I: = 0 to checklistbox1.count-1 do case tbutton (sender ). tag of 1: If checklistbox1.checked [I] Then include (set1, I); 2: checklistbox1.checked [I]: = I in set1; 3: checklistbox1.checked [I]: = true; 4: checklistbox1.checked [I]: = false; end;

  
 

Instance observation tfontstyles set:

{View binary functions} function Tobin (P: pbytearray; B: integer): string; var I, j: integer; begin result: = stringofchar ('0 ', B * 8); for I: = 0 to B-1 do for J: = 0 to 7 do if odd (P ^ [b-1-i] SHR J) then result [I * 8 + 8-J]: = '1'; end; Procedure tform1.button1click (Sender: tobject); var FS: tfontstyles; begin font. style: = [fsbold, fsitalic, fsunderline]; FS: = font. style; text: = Tobin (@ FS, sizeof (FS); end; Procedure tform1.button2click (Sender: tobject); var FS: tfontstyles; begin font. style: = []; FS: = font. style; text: = Tobin (@ FS, sizeof (FS); end;

  
 

Test the tfontstyles set:

Next, we will learn about the tbits class. The "bit" Operation tbits should be the most intuitive.