Delphi basic (routine, routine return value)

I. routine: a unique name in Delphi. Routine is a form of encapsulating the code of a specific function:
1. Process
2. Function
The difference between a procedure and a function is whether there is a return value
Function of routine
1. It can solve the problem of naming conflict
2. Improve code reuse rate
3. Improve code maintainability
III. use history
1. Definition

1 procedure Demo1();    //process
2 begin
3 
4 end;

Definition of function

 1 function Demo2(var a : Integer;var b : Integer) : Integer;  //function
 2 begin
 3   Writeln(a,',',b);
 4 end;
 5 
 6 {The number of transfer parameters is not fixed (multiple parameters)}
 7 procedure  Demo3(const num1 : array of Integer);
 8 var
 9 X,Y : Integer;
10 begin
11 
12 end;
13 
14 begin
15   Demo3([1,2,3,4]);
16   Readln;
17 end.

 

4. Routine return value

 1 {return value: only function has return value, procedure does not have}
 2 function add (num1: Integer; num2: Integer): Integer; / / the last Integer declares the operation result data type
 3 begin
 4 Result: = num1 + num2; / / result get return value
 5 exit; / / terminate
 6 end;
 7 var
 8   Sum : Integer;
 9 begin
10   Sum := Add(2,3);
11   Writeln(Sum);
12   Readln;
13 end.
 1 {Return value: get the operation result by reference}
 2 function Sub1(Num3 : Integer;Num4 : Integer;var sum : Integer) : Integer;
 3 //var sum : Integer Incoming address
 4 begin
 5   sum := Num3 - Num4;
 6   Exit;
 7 end;
 8 
 9 var
10   Sum1 : Integer;
11 begin
12   Sub1(5,3,Sum1);
13   Writeln(Sum1);
14   Readln;
15 end.
 1 {Return value:out}
 2 function mul(Num5:Integer;Num6:Integer;out sum:Integer):Integer;
 3 begin
 4   sum := Num5 * Num6;
 5   Exit;
 6 end;
 7 var
 8   sum : Integer;
 9 begin
10   mul(5,3,sum);
11   Writeln(sum);
12   Readln;
13 end.
1 {get return value by function name}
2 function GetResultByFunName():Integer;
3 begin
4   GetResultByFunName := 1+3;
5 end;
6 begin
7   Writeln(GetResultByFunName());
8   Readln;
9 end.
 1 {overload Function overload: same function name and different parameter list,Use keyword identification}
 2 function Add(Num1 : Integer;Num2 : Integer;var sum : Integer) : Integer;  overload;
 3 begin
 4   sum := Num1 + Num2;
 5   Exit;
 6 end;
 7 
 8 function Add(Num1 : Double;Num2 : Double;out sum : Double) : Double; overload;
 9 
10 begin
11   sum := Num1 + Num2;
12   Exit;
13 end;
14 
15 var
16 //  sum : Integer;
17   sum : Double;
18 begin
19 //  Add(2,3,sum);
20   Add(2.4,2.02132,sum);
21   Writeln(sum);
22   Readln;
23 end.
 1 {forward forward declaration}
 2 function DivFun() : Integer; forward;
 3 
 4 function MilFun() : Integer;
 5 begin
 6   DivFun();
 7 end;
 8 
 9 function DivFun() : Integer;
10 begin
11   Writeln('test');
12 end;
13 begin
14   MilFun();
15   Readln;
16 end.

Tags: Delphi

Posted on Tue, 03 Dec 2019 19:58:19 -0500 by Schlo_50