Editing Generic programming (section)

=====Basic, unconstrained genericity=====
Generic classes are declared with their class name and a list of one or more ''formal generic parameters''. In the following code, class <code lang=Eiffel>LIST</code> has one formal generic parameter <code lang=Eiffel>G</code>

<syntaxhighlight lang="eiffel">
class
    LIST [G]
            ...
feature   -- Access
    item: G
            -- The item currently pointed to by cursor
            ...
feature   -- Element change
    put (new_item: G)
            -- Add `new_item' at the end of the list
            ...
</syntaxhighlight>

The formal generic parameters are placeholders for arbitrary class names that will be supplied when a declaration of the generic class is made, as shown in the two ''generic derivations'' below, where <code lang=Eiffel>ACCOUNT</code> and <code lang=Eiffel>DEPOSIT</code> are other class names. <code lang=Eiffel>ACCOUNT</code> and <code lang=Eiffel>DEPOSIT</code> are considered ''actual generic parameters'' as they provide real class names to substitute for <code lang=Eiffel>G</code> in actual use.

<syntaxhighlight lang="eiffel">
    list_of_accounts: LIST [ACCOUNT]
            -- Account list

    list_of_deposits: LIST [DEPOSIT]
            -- Deposit list
</syntaxhighlight>

Within the Eiffel type system, although class <code lang=Eiffel>LIST [G]</code> is considered a class, it is not considered a type. However, a generic derivation of <code lang=Eiffel>LIST [G]</code> such as <code lang=Eiffel>LIST [ACCOUNT]</code> is considered a type.