Differences between ETL 2nd printing and Eiffel Software implementation

See Also: See also: Differences between standard ECMA-367 and Eiffel Software implementation

"ETL 2nd printing" refers to the book "Eiffel: The Language" (2nd printing), published by Prentice Hall.

Added classes

• New basic classes have been added: INTEGER_8, INTEGER_16, INTEGER_64, CHARACTER_32. INTEGER, CHARACTER, REAL, DOUBLE are aliases to INTEGER_32, CHARACTER_8, REAL_32, REAL_64.

  See Also: Differences between standard ECMA-367 and Eiffel Software implementation

• New TUPLE, ROUTINE, PROCEDURE, FUNCTION, PREDICATE classes required by the agent mechanism.

Added keywords

• Precursor
• reference (now obsolete): a keyword to specify that a type is used as a reference type.
• agent: a keyword used by the agent mechanism.
• create: Instead of using the famous exclamation mark to create an instance of a class, you can use the keyword create. Below you will find a correspondence table between the old and the new syntaxes. The old syntax is still valid, but at some points Eiffel Software will remove it from its implementation:

• Old syntax !! a => new syntax create a
• Old syntax !! a.make => new syntax create a.make
• Old syntax !B! a => new syntax create {B} a
• Old syntax !B! a.make => new syntax create {B} a.make

• note: replacement for the keyword indexing.
• attribute: a keyword to declare attribute body.
• attached: a keyword to specify attached types and object tests.
• detachable: a keyword to specify detachable types.

Added semantics

• Generic creation
• Expression creation: you can now create an object within an expression. For example, you want to create an object and pass it as an argument to a function. Whereas you had to create a local variable, create the object and pass it to the function, you now simply need to pass to the function the creation expression. Here is a small example:
  • Old method:

local a: STRING do ‼ a.make (10) f (a) end

• 'New method:

do f (create {STRING}.make (10)) end

This is also very useful since it can improve the power of assertions.

• Mutually recursive constraints: one can now write class A [H, G->H] or class B [H -> C, G -> ARRAY [H]]. As a result, the declaration A [D, E] is valid only if E is a descendant of D. Similarly, the declaration B [E, ARRAY [D]] is not valid, if E is a descendant of D.
• Tuples
• Agents
• Feature access:
  

local value: INTEGER do value := {MY_CLASS}.value end
The previous call is valid, if and only if:

• value is a feature representing a constant of a basic type (INTEGER, DOUBLE or CHARACTER)
• value is a C/C++/DLL external feature
• value is an IL static external feature

Obsolete constructs

• Explicit values should be used to specify constant attributes instead of keyword unique.

Added external support

Look at the page for C and C++ with the introduction of struct and C++ external features encapsulation.