Data commit

Task/Null-object/M2000-Interpreter/null-object-1.m2000

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+Module CheckWord {
+      Declare Alfa "WORD.APPLICATION"
+      Declare Alfa Nothing
+      Print Type$(Alfa)="Nothing"
+      Try ok {
+            Declare Alfa "WORD.APPLICATION"
+            \\ we can't declare again Alfa
+
+      }
+      If Not Ok Then Print Error$  ' return Bad Object declaration
+}
+CheckWord

Task/Null-object/M2000-Interpreter/null-object-2.m2000

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+Module CheckContainers {
+      \\ Arrays  (A() and B() are value types)
+      Dim A(10)=1, B()
+      \\ B() get a copy of A(), is not a reference type
+      B()=A()
+      \\ we make a pointer to Array
+      B=A()
+      \\ now B is a reference type object
+      Print Len(B)=10  ' ten items
+      B+=10
+      Print A(3)=11, A(7)=11
+      \\ we can change pointer using a pointer to an empty array
+      B=(,)
+      \\ we can erase A() and B()
+      Dim A(0), B(0)
+      Print Len(A())=0, Len(B())=0
+      Print Len(B)=0
+      B=(123,)
+      \\ B() is a value type so get a copy
+      B()=B
+      Print Len(B)=1, B(0)=123
+      \\ Using Clear we pass a new empty array
+      Clear B
+      Print Type$(B)="mArray"
+      Print Len(B)=1, B(0)=123
+
+
+      \\ Inventrories. Keys must be unique (for normal inventories)
+      Inventory M=1,2,3,4:=400,5
+      Print M
+      Clear M
+      Inventory M=1,2,3,4,5
+      Print M
+
+      \\ Inventory Queue can have same keys.
+      Inventory Queue N=1,1,2:="old",2:="ok",3
+      If Exist(N,2) Then Print Eval$(N)="ok", Eval(N!)=3 ' 4th item
+      Clear N
+      Print Len(N)=0, Type$(N)="Inventory"
+
+      \\ Stack Object
+       Z=Stack:=1,2,3
+       Stack Z {
+            While not empty {Print Number}
+      }
+      Print Len(Z)=0
+      Z=Stack((Stack:=1,2,3,4),Stack:=20,30,40 )
+      Print Len(Z)=7
+      Print Z    ' 1 2 3 4 20 30 49
+      Z=Stack  ' This is an empty stacl
+      Print Len(Z)=0
+      Print Type$(Z)="mStiva"
+}
+CheckContainers

Task/Null-object/M2000-Interpreter/null-object-3.m2000

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+class something {
+}
+class alfa as something {
+	x=10, y=20
+}
+a->alfa()
+Print a is type alfa = true
+Print a is type something = true
+a->0&
+Print a is type null = true
+\\ beta is a named object, is static
+group beta {
+type: something, alfa
+	x=10, y=20
+}
+Print beta is type alfa = true
+Print beta is type something = true
+\\ now a is a pointer as a weak reference to beta
+a->beta
+print a is type alfa = true
+print a is type something = true
+a=pointer()   ' same as a->0&
+Print a is type null = true
+\\ now a is a pointer of a copy of beta
+a->(beta)
+print a is type alfa = true
+print a is type something = true
+a=pointer()   ' same as a->0&
+Print a is type null = true