Boost::optional<bool> dereference

Question

I am reviewing some code and have something like this:

boost::optional<bool> isSet = ...;
... some code goes here...
bool smthelse = isSet ? *isSet : false;

So my question is, is the last line equivalent to this:

bool smthelse = isSet; 

Answer 1

Here's the table:

boost::optional<bool> isSet | none | true | false |
----------------------------|------|------|-------|
isSet ? *isSet : false;     | false| true | false |
isSet                       | false| true | true  |

As you can see difference in the last column, where isSet has been assigned the boolean value false.

Alternatively, you can use isSet.get_value_or(false);.