Anonymous Function

Anonymous functions don’t have names. I first learned about this at Marianopolis College programming class, but it was actually super easy.

I wonder if every single person in that class went into Software Engineering / Computer Science lol.

Python

Don’t know if this is the perfect syntax for it.

a = lambda x: x+2

C++

https://stackoverflow.com/questions/7100889/how-can-i-access-local-variables-from-inside-a-c11-anonymous-function

Used for the first time when I was trying to write ORB-SLAM from scratch.

To access local variables from within anonymous function, you need a Closure.

• Source: https://stackoverflow.com/questions/7100889/how-can-i-access-local-variables-from-inside-a-c11-anonymous-function

float tot = std::accumulate(weights.begin(), weights.end(), 0);
std::transform(weights.begin(), weights.end(), [tot](float x)->float{return(x/tot);});

In this case tot is captured by value. C++11 lambdas support capturing by:

1. value [x]
2. reference [&x]
3. any variable currently in scope by reference [&]
4. same as 3, but by value [=]

You can mix any of the above in a comma separated list [x, &y].

Tip

Using the third way [&] is generally considered bad practice, because you aren’t explicit about the variables that you want to use.