Schemas Quiz

1. When you need to add a new method to a class, on what basis should you decide whether to declare it as a function or as a schema?

If the method needs to modify something, it must be declared as a schema, since functions cannot modify anything.

If the method merely needs to compute and return one or more values, it should be declared as a function.

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2. You are given the following partial class declaration:

class ListOfIntegers ^=
abstract
  var list: seq of int;
interface
  build{}
    post list! = seq of int{};
end;

Write a method to return the number of items in the list and a method to add a new item to the end of the list.

Insert the following in the interface section:

  function itemCount: nat
    ^= #list;

  schema !addItem(item: int)
    post list! = list.append(item);

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