Macro next_gen::gen_iter

macro_rules! gen_iter {
    (
        for $pat:pat in $generator:tt ($($args:expr),* $(,)?) $block:block
    ) => { ... };
    (
        for $pat:pat in $generator:tt $block:block
    ) => { ... };
}

Emulate a for-loop iteration over a generator. The call itself evaluates to the Return value of the Generator.

Example

use ::next_gen::prelude::*;

type Question = &'static str;
type Answer = i32;

#[generator(Question)]
fn answer () -> Answer
{
    yield_!("What is the answer to life, the universe and everything?");
    42
}

let ret = gen_iter!(
    for question in answer() {
        assert_eq!(
            question,
            "What is the answer to life, the universe and everything?",
        );
    }
);
assert_eq!(ret, 42);

// You can also give it an already instanced generator:

mk_gen!(let mut generator = answer());
assert_eq!(
    generator.as_mut().resume(),
    ::next_gen::GeneratorState::Yield(
        "What is the answer to life, the universe and everything?"
    ),
);

let ret = gen_iter!(
    for _ in generator {
        unreachable!();
    }
);
assert_eq!(ret, 42);

---

Note that you do not need this macro when you don't care about the return value:

use ::next_gen::prelude::*;

type Question = &'static str;
type Answer = i32;

#[generator(Question)]
fn answer () -> Answer
{
    yield_!("What is the answer to life, the universe and everything?");
    42
}

mk_gen!(let generator = answer());

for question in generator {
    assert_eq!(
        question,
        "What is the answer to life, the universe and everything?",
    );
}