Editing Eiffel (programming language) (section)

===Tuples===
Tuples types may be viewed as a simple form of class, providing only attributes and the corresponding "setter" procedure. A typical tuple type reads

<syntaxhighlight lang="eiffel">
   TUPLE [name: STRING; weight: REAL; date: DATE]
</syntaxhighlight>

and could be used to describe a simple notion of birth record if a class is not needed. An instance of such a tuple is simply a sequence of values with the given types, given in brackets, such as

<syntaxhighlight lang="eiffel">
   ["Brigitte", 3.5, Last_night]
</syntaxhighlight>

Components of such a tuple can be accessed as if the tuple tags were attributes of a class, for example if <code>t</code> has been assigned the above tuple then <code>t.weight</code> has value 3.5.

Thanks to the notion of assigner command (see below), dot notation can also be used to assign components of such a tuple, as in

<syntaxhighlight lang="eiffel">
   t.weight := t.weight + 0.5
</syntaxhighlight>

The tuple tags are optional, so that it is also possible to write a tuple type as <code>TUPLE [STRING, REAL, DATE]</code>. (In some compilers this is the only form of tuple, as tags were introduced with the ECMA standard.)

The precise specification of e.g. <code>TUPLE [A, B, C]</code> is that it describes sequences of ''at least'' three elements, the first three being of types <code>A</code>, <code>B</code>, <code>C</code> respectively. As a result, <code>TUPLE [A, B, C]</code> conforms to (may be assigned to) <code>TUPLE [A, B]</code>, to <code>TUPLE [A]</code> and to <code>TUPLE</code> (without parameters), the topmost tuple type to which all tuple types conform.