B

Task/Abstract-type/BBC-BASIC/abstract-type.bbc

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+      INSTALL @lib$+"CLASSLIB"
+
+      REM Declare a class with no implementation:
+      DIM abstract{method}
+      PROC_class(abstract{})
+
+      REM Inherit from the abstract class:
+      DIM derived{member%}
+      PROC_inherit(derived{}, abstract{})
+      PROC_class(derived{})
+
+      REM Provide an implementation for the derived class:
+      DEF derived.method : PRINT "Hello world!" : ENDPROC
+
+      REM Instantiate the derived class:
+      PROC_new(instance{}, derived{})
+
+      REM Test by calling the method:
+      PROC(instance.method)