CODEWITHSUNDEEP
c++boostboost-phoenix
alxprogger
alxprogger

Reputation: 87

Motivation to use boost::phoenix::val?

Please, could you show situations, where the use of boost::phoenix::val is indispensable (or at least very handy), not just optional. Boost doc doesn't go far beyond examples like

std::cout<<boost::phoenix::val(3)();   //output is 3.

When and why one would prefer 

boost::phoenix::val(t)();

instead of just

t;

Upvotes: 1

Views: 284

Answers (1)

sehe
sehe

Reputation: 393114

You wouldn't.

You'd prefer it if you required a (lazy) callable:

template <typename F>
void print_three_times(F f) {
    std::cout << 3*f() << "\n";
}

Now you can call it using

print_three_times(phx::val(3));

int i;
std::cin >> i;
print_three_times(phx::val(i));

Also you can use it to coerce any reference to a phoenix lazy actor:

std::cout << 3; // not an actor
std::cout << val(3); // a lazy actor

Upvotes: 2

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