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Author:manus

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Date:2009-12-07T22:28:01.000000Z


git-svn-id: https://svn.eiffel.com/eiffel-org/trunk@367 abb3cda0-5349-4a8f-a601-0c33ac3a8c38
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manus
2009-12-07 22:28:01 +00:00
parent 9999e50aec
commit 9206abfd4b
2 changed files with 12 additions and 3 deletions
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documentation/current/method/eiffel-tutorial-et/et-dynamic-structure-execution-model.wiki
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@@ -447,7 +447,7 @@ As with assignment, there is also a form that works on objects rather than refer
</code>
will return true when <code>x</code> and <code>y</code> are both non-void and attached to field-by-field identical objects. This can be true even when <code>x = y</code> is not, for example, in the figure, ''before'' the assignment, if the two objects shown are field-by-field equal.
The expression <code>x.is_equal (y)</code> can be written alternatively in a notation similar in form to <code>x = y</code> . The expression:
The expression <code>x.is_equal (y)</code> can be written alternatively, using the ''tilde'' ('~") character, in a notation similar in form to <code>x = y</code> . The expression:
<code>
x ~ y
</code>
@@ -459,6 +459,8 @@ A more general variant of <code>is_equal</code> is used under the form:
</code>
This is always defined, even if <code>x</code> is void, returning true whenever <code>is_equal</code> would but also if <code>x</code> and <code>y</code> are both void. (In contrast, <code>x.is_equal (y)</code> is not defined for void <code>x</code> and would, if evaluated, yield an exception as explained in [[ET: Design by Contract (tm), Assertions and Exceptions#Exception_handling|"Exception handling"]] below.)
{{note|The <code>~</code> operator performs an object equality comparison, using the (possibly redefined) version of feature <code>is_equal</code> that is appropriate for the operand types. The operand types must be the same, or the result will be <code>False</code>. As such, the use of <code>~</code> is preferred to over the use of direct use of either <code>x.is_equal (y)</code> or <code>equal (x, y)</code>, which can be susceptible to [[ET: Inheritance#Catcalls|catcalls]].}}
<code>Void</code> denotes a void reference. So you can make <code>x</code> void through the assignment
<code>
x := Void