Vergleich der Programmierkonzepte verschiedener Sprachen anhand von Codebeispielen

Im Folgenden wird Beispielcode für allgemeine Programmierkonzepte angegeben, die nicht durch ein Schlüsselwort zusammengefasst werden können.Weitere Informationen finden Sie unter Vergleich der Schlüsselwörter in verschiedenen Sprachen.

Codebeispiele werden für die folgenden Aufgaben dargestellt:

• Zuweisungsanweisungen

• Kommentare

• Bedingte Anweisungen

• Deklarieren von Variablen

• For-Schleifen

• Generische Typen

• Verbergen von Basisklassenmembern

• Initialisieren von Werttypen

• Parameterübergabe durch Verweis

• Parameterübergabe durch Wert

• Auswahlanweisungen

• Objektreferenz auf "Nothing" setzen

• Strukturierte Ausnahmebehandlung

• While-Schleifen

Deklarieren von Variablen

Visual Basic

Dim x As Integer
Public x As Integer = 10
Dim x = 10

C++

int x;
int x = 10;
var x = 10;

C#

int x;
int x = 10;

F#

let x = 10

Kommentare

Visual Basic

' comment
x = 1   ' comment
Rem comment 

C++

// comment

/* multiline
 comment */

C#

// comment
/* multiline
 comment */

F#

// comment
(* multiline
 comment *)

Zuweisungsanweisungen

Visual Basic

nVal = 7

C++

nVal = 7;

C#

nVal = 7;

F#

nVal <- 7

Bedingte Anweisungen

Visual Basic

If nCnt <= nMax Then
   nTotal += nCnt  ' Same as nTotal = nTotal + nCnt.
   nCnt += 1       ' Same as nCnt = nCnt + 1.
Else
   nTotal += nCnt
   nCnt -= 1       
End If

C++

if(nCnt < nMax) {
 nTotal += nCnt;
 nCnt++;
 }
else {
   nTotal += nCnt;
   nCnt --;    
 };

C#

if (nCnt <= nMax)
{
   nTotal += nCnt;
   nCnt++;
}
else
{
   nTotal +=nCnt;
   nCnt--;
}

F#

if (nCnt <= nMax) then
    nTotal <- nTotal + nCnt
    nCnt <- nCnt + 1
else
    nTotal <- nTotal + nCnt
    nCnt <- nCnt - 1

Auswahlanweisungen

Visual Basic

Select Case n
   Case 0
      MsgBox ("Zero")  
     ' Visual Basic exits the Select at the end of a Case.
   Case 1
      MsgBox ("One")
   Case 2 
      MsgBox ("Two")
   Case Else
      MsgBox ("Default")
End Select

C++

switch(n) {
 case 0:
  printf_s("Zero\n");
  break;
 case 1:
  printf_s("One\n");
  break;
 case 2:
  printf_s("Two\n");
  break;
 default:
  printf_s("?\n");}

C#

switch(n) 
{
   case 0:
      Console.WriteLine("Zero");
      break;
   case 1:
      Console.WriteLine("One");
      break;
   case 2:
      Console.WriteLine("Two");
      break;
   default:
      Console.WriteLine("?");
      break;
}

F#

Übereinstimmung von n mit

| 0 -> Console.WriteLine("Zero")

| 1 -> Console.WriteLine("One")

| 2 -> Console.WriteLine("Two")

| _ -> Console.WriteLine("?")

For-Schleifen

Visual Basic

For n = 1 To 10 
   MsgBox("The number is " & n)
Next

For Each prop In obj
    prop = 42
Next prop

C++

for(int n=1; n<11; n++)
 printf_s("%d\n",n);

C#

for (int i = 1; i <= 10; i++) 
   Console.WriteLine("The number is {0}", i);
foreach (int i in testArr) 
{
   Console.WriteLine(i);
}

F#

for i = 1 to 10 do
    printfn "%d" i
for i in testCollection do
    printfn "%d" i

Verbergen von Basisklassenmembern

Visual Basic

Public Class BaseCls
   Public Z As Integer = 100   ' The element to be shadowed
   public Sub Test()
      System.Console.WriteLine("Test in BaseCls")
   End Sub
End Class

Public Class DervCls
   Inherits BaseCls
   Public Shadows Z As String = "*"   ' The shadowing element.
   public Shadows Sub Test()
      System.Console.WriteLine("Test in DervCls")
   End Sub
End Class

Public Class UseClasses
   Dim BObj As BaseCls = New DervCls()   ' DervCls widens to BaseCls. 
   Dim DObj As DervCls = New DervCls()   ' Access through derived class.
   Public Sub ShowZ()
      System.Console.WriteLine("Accessed through base class: " & BObj.Z)
      System.Console.WriteLine("Accessed through derived class: " & DObj.Z)
      BObj.Test()
      DObj.Test()
   End Sub 
End Class

C++

#using <mscorlib.dll>
#include <stdio.h>
public __gc class BaseCls
{
public:
   int Z;   // The element to be hidden
   void Test()
   {
      printf_s("Test in BaseCls\n");
   }

};

public __gc class DervCls : public BaseCls
{
public:
   char Z;   // The hiding element
   void Test()
   {
      printf_s("Test in DervCls\n");
   }

};

public __gc class UseClasses
{
public:
   BaseCls * BObj;   // DervCls widens to BaseCls
   DervCls * DObj;   // Access through derived class
   void ShowZ()
   {
      BObj = new DervCls;
      BObj->Z = 100;
      DObj = new DervCls;
      DObj->Z = '*';
      printf_s("Accessed through base class: %d\n", BObj->Z);
      printf_s("Accessed through derived class: %c\n", DObj->Z);
      BObj->Test();
      DObj->Test();
   }
};

C#

public class BaseCls
{
   public int Z = 100;   // The element to be hidden
   public void Test()
   {
      System.Console.WriteLine("Test in BaseCls");
   }
}

public class DervCls : BaseCls
{
   public new string Z = "*";   // The hiding element
   public new void Test()
   {
      System.Console.WriteLine("Test in DervCls");
   }
}

public class UseClasses
{
   BaseCls BObj = new DervCls();   // DervCls widens to BaseCls
   DervCls DObj = new DervCls();   // Access through derived class
   public void ShowZ()
   {
      System.Console.WriteLine("Accessed through base class: {0}", BObj.Z);
      System.Console.WriteLine("Accessed through derived class: {0}", DObj.Z);
      BObj.Test();
      DObj.Test();
   }
}

F#

type BaseCls() =
    member this.Z = 100
    member this.Test() =
        System.Console.WriteLine("Test in BaseCls")

type DervCls() =
    inherit BaseCls()
    member this.Z = "*"
    member this.Test() =
       System.Console.WriteLine("Test in DervCls")

type UseClasses() =
    let BObj : BaseCls = new DervCls() :> BaseCls
    let DObj : DervCls = new DervCls()
    member this.ShowZ() =
        System.Console.WriteLine("Accessed through base class: {0}", BObj.Z)
        System.Console.WriteLine("Accessed through derived class: {0}", DObj.Z)
        BObj.Test()
        DObj.Test()

let useClassesObj = new UseClasses()
useClassesObj.ShowZ()

While-Schleifen

Visual Basic

While n < 100 ' Test at start of loop.
   n += 1     ' Same as n = n + 1.
End While '

C++

while(int n < 100)
   n++;

C#

while (n < 100)
   n++;

F#

while n < 100 do
     n <- n + 1

Parameterübergabe durch Wert

Visual Basic

Public Sub ABC(ByVal y As Long) ' The argument Y is passed by value.
' If ABC changes y, the changes do not affect x.
End Sub
   
ABC(x) ' Call the procedure.
' You can force parameters to be passed by value, regardless of how 
' they are declared, by enclosing the parameters in extra parentheses.
ABC((x))

C++

testMethod(i,j);

C#

/* Note that there is no way to pass reference types (objects) strictly by value. 
You can choose to either pass the reference (essentially a pointer), 
or a reference to the reference (a pointer to a pointer).*/
// The method:
void ABC(int x)
{
   ...
}
// Calling the method:
ABC(i);

F#

let ABC(x) =
   ...
ABC(i)

Parameterübergabe durch Verweis

Visual Basic

Public Sub ABC(ByRef y As Long) 
' The parameter y is declared by by referece:
' If ABC changes y, the changes are made to the value of x.
End Sub

ABC(x) ' Call the procedure.

C++

// Prototype of ABC that takes a pointer to integer.
int ABC(long *py);
ABC(&VAR);
// Prototype of ABC that takes a reference to integer.
int ABC(long &y);
ABC(VAR);

C#

/* Note that there is no way to pass reference types (objects) strictly by value. 
You can choose to either pass the reference (essentially a pointer), 
or a reference to the reference (a pointer to a pointer).*/
/* Note also that unsafe C# methods can take pointers just like C++ methods. 
For details, see <MSHelp:link keywords="vclrfUnsafe" TABINDEX="0">unsafe</MSHelp:link>. */
// The method:
void ABC(ref int x)
{
   ...
}
// Calling the method:
ABC(ref i);

F#

let ABC(x : int byref) =
   ...
ABC(&i)

Strukturierte Ausnahmebehandlung

Visual Basic

Try
   If x = 0 Then
      Throw New Exception("x equals zero")
   Else
      Throw New Exception("x does not equal zero")
   End If
Catch err As System.Exception
   MsgBox("Error: " & Err.Description)
Finally
   MsgBox("Executing finally block.")
End Try

C++

      __try{
      if (x == 0)
         throw new Exception ("x equals zero");
      else
         throw new Exception ("x does not equal zero");
         }
      __catch(Exception e)
{
            Console.WriteLine("Caught Exception"); 
      }
      __finally
{
         Console.WriteLine("Executing finally block");
      }

C#

// try-catch-finally
try
{
   if (x == 0)
      throw new System.Exception ("x equals zero");
   else
      throw new System.Exception ("x does not equal zero");
}
catch (System.Exception err)
{
   System.Console.WriteLine(err.Message);
}
finally
{
   System.Console.WriteLine("executing finally block");
}

F#

try
    try
        if x = 0 then
             failwith "x equals zero"
        else
             failwith "x does not equal zero"
    with
        | Failure(msg) -> System.Console.WriteLine(msg)
finally
    printfn "executing finally block"

Objektreferenz auf "Nothing" setzen

Visual Basic

o = Nothing

C++

o = nullptr;  // when compiling with /clr

C#

o = null;

F#

// for an option type
o <- None
// when you really want a null value
o <- null

Initialisieren von Werttypen

Visual Basic

Dim dt as New System.DateTime(2001, 4, 12, 22, 16, 49, 844)

C++

System::DateTime dt = System::DateTime(2001, 4, 12, 22, 16, 49, 844);

C#

System.DateTime dt = new System.DateTime(2001, 4, 12, 22, 16, 49, 844);

F#

let dt = new System.DateTime(2001, 4, 12, 22, 16, 49, 844)

Generische Typen

Visual Basic

' Define a generic type
Public Class classMaker(Of t)
' Constrain a type parameter
Public Class classMaker(Of t As IComparable)
' Create an object from a generic type
Dim integerClass As New classMaker(Of Integer)

C++

// Define a generic type
generic <typename T> ref class testList { ... };
// Constrain a type parameter
generic <typename T> where T : IComparable<T>
ref class testList { ... };
// Create an object from a generic type
testList<int>^ list = gcnew testList<int>();

C#

// Define a generic type
public class testList<T>{...}
// Constrain a type parameter
public class testList<T> where T : IComparable<T>
// Create an object from a generic type
testList<int> list = new testList<int>();

F#

// Define a generic type
type testList<'T> =
    ...
// Constraint a type parameter
type testList<'T when 'T :> IComparable<'T>>
// Create an object from a generic type
let list1 = new testList<int>()

Siehe auch

Referenz

Vergleich der Schlüsselwörter in verschiedenen Sprachen

In verschiedenen Sprachen verglichene Datentypen

Operatorenvergleich in verschiedenen Sprachen

In zahlreichen Sprachen und Bibliotheken verglichene Steuerelemente und programmierbare Objekte

Weitere Ressourcen

Entsprechungen in verschiedenen Sprachen