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Subject:
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copty constructor vs assignment operator
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Posted By:
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mitjit123
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Post Date:
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7/11/2006 12:41:34 AM
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In chapter 8 ,regarding the concept on page 180 181
In case of
string s1,
s1 = myCell2.getString();
the copy constructor is called for creating the temporary obj
and then the assignment operator.
Then in case of
String s2 = myCell3.getString();
2 copy constructors should be called . One for creating temporary object and another for s2.
But copy constructor is getting called only once.
Why is this?
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Reply By:
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klep
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Reply Date:
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9/3/2006 2:10:11 AM
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In the first example, s1 is already constructed (on the previous line) so the assignment operator will be used to assign the temporary result object to s1.
In the second example, the compiler recognizes that s2 is just being built, so it uses the copy constructor. The compiler is allowed to omit the temporary return object in this case as a performance enhancement -- there's really no need to call the copy constructor twice when the result value can be copied directly into s2.
Hope that helps!
Scott
----
Scott J. Kleper
Author, "Professional C++"
(Wrox, 2005)
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