Pass a lambda into the second clause of a ternary operator - c++

Question

I am trying make ternary operator work with lambda. Following is the logic that I want to cast into a ternary operation
if (boolean_condition_var == false) {
RandomMethod();
}
// From here some logic to execute
int i = 0;
// blah blah logic
Following is how I am trying to make it work after reading through this link.
boolean_condition_var == false ? RandomMethod() : std::function<void(void)>([this](){
// execute some logic here
int i = 0;
//blah blah logic
});
But I am getting the following error:
Issue:
error: left operand to ? is void, but right operand is of type 'std::function<void ()>'
boolean_condition_var == false ? RandomMethod() : std::function<void(void)>([this](){ int i = 0; });
Question:
How can I pass a lambda into the second clause of my ternary operator?

Answer 1

Since you are not calling the lambda, it makes little sense to create it. What you are trying to do is equivalent to
boolean_condition_var ? void(0) : RandomMethod();
On the other hand, if you want to call the lambda, use the call operator:
boolean_condition_var? ([this](){...your code...}) ( ) : RandomMethod();
// ^
// |
//--------------------------------------------------+
There's no need to cast anything to std::function.
A plain old if-then-else statement would be more welcome here.
On the third hand, if you want your ternary operator to return a callable, you probably need something like
using voidf = std::function<void(void)>;
auto result = boolean_condition_var?
voidf([this](){...your code...}):
voidf([this](){RandomNethod();});
.... result();
Capturing boolean_condition_var by value and moving the condition into the (now single) lambda could be more readable and more efficient though.

Answer 2

How can I pass a lambda into the second clause of my ternary operator?
Using comma operator ?
boolean_condition_var == false
? (RandomMethod(), 0)
: (std::function<void(void)>([this](){ /*...*/ })(), 0);
Or, I suppose better,
std::function<void(void)> logicElse { [this](){ /*...*/ } };
boolean_condition_var == false
? (RandomMethod(), 0)
: (logicElse(), 0);