Question

I am translating some code from Python to C++. I came across the following:

set(x for listX in listY for x in listX)

I am quite well-versed in C++ and know some basic constructs in Python. In the above code, I know that a set is being created but I do not understand the code inside the brackets. Any help?

Answer 1

listY is probably something like the structure below, so the expanded code is:

listY = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
result = set()
for listX in listY:
    for x in listX:
        result.add(x)

notice: sets won’t allow duplicate entries