Call by reference of bool types

Question

How can I change this piece of code to a working one?!

#include <iostream>

void foo( bool &b )  // ERROR in passing argument 1 of ‘void foo(bool&)’
{
   std::cout << b << '\n';
}

int main()
{
  foo( false );   // ERROR invalid initialization of non-const reference of type ‘bool&’ from a temporary of type ‘bool’
  return 0;
}

Please note that I want to use call by reference method using &b.

Also note this has nothing to do with the type being `bool`. — juanchopanza, May 24 '14 at 14:56
@keyser: Yes that is also possible based on michaelBurns's answer — mahmood, May 24 '14 at 15:02

score 2 · Answer 1 · edited May 24 '14 at 14:59

2

call by reference requires an address, you're passing a constant. why no

bool aValue;
aValue = false;
foo(aValue);

edited May 24 '14 at 14:59

keyser

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answered May 24 '14 at 14:50

michaelBurns

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That is also possible. – mahmood May 24 '14 at 14:52
It doesn't really require "an address". – juanchopanza May 24 '14 at 15:00
forgive me if im wrong, but is it not the memory location on the stack/heap that is passed to the function, as opposed to the value that resides at the memory location? – michaelBurns May 24 '14 at 15:05
That would be an implementation detail. Semantically, a reference is just an alias for an object. In this case, what is needed is an *lvalue*. – juanchopanza May 24 '14 at 15:07

score 1 · Accepted Answer · answered May 24 '14 at 14:52

1

foo( false );

this calls foo with a temporary object of type bool.

You cannot bind a temporary to non-const reference thus the error. It is possible in case of const reference

void foo( const bool &b );
//...
foo( false ); // OK

In your case it seems that you don't want to change an object being passed to the function but just to print it. Then there is no need to pass a reference, you can just pass object by value.

void foo( bool b ) { std::cout << b;}
//...
foo( false ); // OK

answered May 24 '14 at 14:52

4pie0

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`Then there is no need to pass a reference, you can just pass object by value.` Only true with small objects. What if the object passed was a large datastructure? still better to have &. – cade Mar 22 '17 at 05:30

Call by reference of bool types

2 Answers2