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/// Pins a local to the stack. /// /// This is used by [`mk_gen`]`!` to get a pollable generator without going /// through a heap allocation (as [`Box::pin`] would do). #[macro_export] macro_rules! stack_pinned { ( $var:ident ) => ( let (ref $var,) = ($var,); let $var = unsafe { /// # Safety /// /// - This is pin_utils' `pin_mut!` macro: the shadowing ensures /// there is no longer access to the original stack variable, /// which is thus impossible to move or forget. extern {} $crate::core::pin::Pin::new_unchecked($var) }; ); ( mut $var:ident ) => ( let (ref mut $var,) = ($var,); #[allow(unused_mut)] let mut $var = unsafe { /// # Safety /// /// - This is pin_utils' `pin_mut!` macro: the shadowing ensures /// there is no longer access to the original stack variable, /// which is thus impossible to move or forget. extern {} $crate::core::pin::Pin::new_unchecked($var) }; ); } /// Instances a generator and pins it(required to be able to poll it). /// /// By default it pins to the stack, but by using `box` it can pin to the heap /// (necessary when wanting to return the generator itself). /// /// # Usage /// /// > `mk_gen!(let $(mut)? <varname> = $(box)? <generator fn> (<args>));` /// /// # Example /// /// ```rust /// use ::next_gen::prelude::*; /// /// #[generator(bool)] /// fn toggler (initial: bool) /// { /// use ::core::ops::Not; /// /// let mut current = initial; /// loop { /// yield_!(current); /// current = current.not(); /// } /// } /// /// mk_gen!(let generator = toggler(true)); /// // a generator is not an iterator but an iterable: /// let mut iterator = generator.into_iter(); /// /// assert_eq!(iterator.next(), Some(true)); /// assert_eq!(iterator.next(), Some(false)); /// assert_eq!(iterator.next(), Some(true)); /// assert_eq!(iterator.next(), Some(false)); /// assert_eq!(iterator.take(10_000).count(), 10_000); /// ``` /// /// See [`GeneratorFn`] for more examples. #[macro_export] macro_rules! mk_gen { (@input let [$($mut:tt)?] $var:ident = box $generator:tt ( $($args:expr),* $(,)? ) $(;)? ) => ( let generator = $generator; let var = $crate::GeneratorFn::empty(); let mut $var = ::std::boxed::Box::pin(var); $var .as_mut() .init( generator, ($($args, )*), ) ; ); (@input let [$($mut:tt)?] $var:ident = $generator:tt ( $($args:expr),* $(,)? ) $(;)? ) => ( let var = $crate::GeneratorFn::empty(); $crate::stack_pinned!(mut var); var .as_mut() .init( $generator, ($($args, )*), ) ; let $($mut)? $var = var; ); ( let mut $($tt:tt)* ) => ( $crate::mk_gen!(@input let [mut] $($tt)*) ); ( let $($tt:tt)* ) => ( $crate::mk_gen!(@input let [] $($tt)*) ); } /// Emulate a `for`-loop iteration over a generator. The call itself evaluates /// to the [`Return`][`crate::Generator::Return`] value of the [`Generator`][ /// `crate::Generator`]. /// /// # Example /// /// ```rust /// 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: /// /// ```rust /// 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?", /// ); /// } /// ``` #[macro_export] macro_rules! gen_iter { ( for $pat:pat in $generator:tt ($($args:expr),* $(,)?) $block:block ) => ({ $crate::mk_gen!(let generator = $generator ($($args),*)); $crate::gen_iter!( for $pat in generator $block ) }); ( for $pat:pat in $generator:tt $block:block ) => (match $generator { mut generator => { use $crate::{ core::pin::Pin, Generator, GeneratorState, }; let mut resume_generator = || -> GeneratorState<_, _> { Generator::resume( Pin::as_mut(&mut generator) ) }; loop { match resume_generator() { | GeneratorState::Yield($pat) => $block, | GeneratorState::Return(ret) => break ret, } } }}); }