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CONSTRET.CPP
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1995-02-23
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64 lines
// File from page 282 in "Thinking in C++" by Bruce Eckel
//////////////////////////////////////////////////
// From the compressed package ECKELT01.ZIP 2/21/95
// Copyright (c) Bruce Eckel, 1995
// Source code file from the book "Thinking in C++",
// Prentice Hall, 1995, ISBN: 0-13-917709-4
// All rights reserved EXCEPT as allowed by the following
// statements: You may freely use this file for your own
// work, including modifications and distribution in
// executable form only. You may copy and distribute this
// file, as long as it is only distributed in the complete
// (compressed) package with the other files from this
// book and you do not remove this copyright and notice.
// You may not distribute modified versions of the source
// code in this package. This package may be freely placed
// on bulletin boards, internet nodes, shareware disks and
// product vendor disks. You may not use this file in
// printed media without the express permission of the
// author. Bruce Eckel makes no
// representation about the suitability of this software
// for any purpose. It is provided "as is" without express
// or implied warranty of any kind. The entire risk as to
// the quality and performance of the software is with
// you. Should the software prove defective, you assume
// the cost of all necessary servicing, repair, or
// correction.
// If you think you've found an error, please
// email all modified files with loudly commented changes
// to: eckel@aol.com (please use the same
// address for non-code errors found in the book).
//////////////////////////////////////////////////
//: CONSTRET.CPP -- Constant return by value
// Result cannot be used as an lvalue
class X {
int i;
public:
X(int I = 0) : i(I) {}
void modify() { i++; }
};
X f5() {
return X();
}
const X f6() {
return X();
}
void f7(X& x) { // Pass by non-const reference
x.modify();
}
main() {
f5() = X(1); // OK -- non-const return value
f5().modify(); // OK
f7(f5()); // OK
// Causes compile-time errors:
//! f6() = X(1);
//! f6().modify();
//! f7(f6());
}