C++11 Change `auto` Lambda to a different Lambda?

Say I have the following variable containing a lambda:

auto a = [] { return true };

And I want a to return false later on. Could I do something along the lines of this?

a = [] { return false };

This syntax gives me the following errors:

binary '=' : no operator found which takes a right-hand operand of type 
'main::<lambda_a7185966f92d197a64e4878ceff8af4a>' (or there is no acceptable conversion)

IntelliSense: no operator "=" matches these operands
        operand types are: lambda []bool ()->bool = lambda []bool ()->bool

Is there any way to achieve something like this? I would like to change the auto variable to a different lambda. I'm relitively a beginner so I may be missing some knowledge about auto or lambdas. Thanks.