Composability of STL algorithms

Question

The STL algorithms are a pretty useful thing in C++. But one thing that kind of irks me is that they seem to lack composability.

For example, let\'s say I have a v

Answer 1

Not sure if this is still active, but... A new light wait header only lib that does what you describe. Doc talks about lazy evaluation and com compossible generators.

Doc snippet:

• Read in up to 10 integers from a file "test.txt".
• filter for the even numbers, square them and sum their values.

    int total = lz::read(ifstream("test.txt")) | lz::limit(10) |
                lz::filter([](int i) { return i % 2 == 0; }) |
                lz::map([](int i) { return i *  i; }) | lz::sum();

you can split that line up into multiple expressions.

    auto numbers = lz::read(ifstream("test.txt")) | lz::limit(10);
    auto evenFilter = numbers | lz::filter([](int i) { return i % 2 == 0; });
    auto squares = evenFilter | lz::map([](int i) { return i *  i; });
    int total = squares | lz::sum();

• Even though this expression is split over multiple variable assignments, it is not any less efficient.
• Each intermediate variable simply describes a unit of code to be executed. All held in stack.

https://github.com/SaadAttieh/lazyCode