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//! A helper trait to improve the ergonomics when working with multiple [`Option`]s. After //! importing [`TupleCombinator`], you can treat a tuple of `Option`s as one `Option`. //! //! # Example //! //! ``` //! use tuple_combinator::TupleCombinator; //! //! fn main() { //! let tuples = (Some(1), Some(2), Some(3)); //! //! assert_eq!(tuples.map(|(a,b,c)| a + b + c), Some(6)); //! assert_eq!(tuples.and_then(|(a,b,c)| Some(a + b - c)), Some(0)); //! assert_eq!(tuples.transpose(), Some((1,2,3))); //! assert_eq!((Some(1), None).map(|(a, b): (i32, i32)| 100), None); //! } //! ``` use std::any::Any; /// The traits that provides helper functions for tuples. This trait implementation mirros most of /// the methods defined in [`Option`]. #[doc(inline)] pub trait TupleCombinator: Sized { type Tuple; /// Transposes a tuple of [`Option`]s into an `Option` of tuples. This function returns `None` /// if any of the `Option` is `None`. /// ``` /// # use tuple_combinator::TupleCombinator; /// let left = (Some("foo"), Some(123)); /// assert_eq!(left.transpose(), Some(("foo", 123))); /// ``` fn transpose(self) -> Option<Self::Tuple>; /// See [`Option::map`]. /// /// # Examples /// /// ``` /// # use tuple_combinator::TupleCombinator; /// let tuples = (Some("foo"), Some("bar")); /// assert_eq!(tuples.map(|(a, b)| format!("{}{}", a, b)).unwrap(), "foobar"); /// ``` fn map<U, F: FnOnce(Self::Tuple) -> U>(self, f: F) -> Option<U> { self.transpose().map(f) } /// See [`Option::expect`]. /// /// # Examples /// /// ``` /// # use tuple_combinator::TupleCombinator; /// let tuples = (Some("foo"), Some(123)); /// assert_eq!(tuples.expect("should not panic"), ("foo", 123)); /// ``` /// /// ```{.should_panic} /// # use tuple_combinator::TupleCombinator; /// let tuples: (_, Option<i32>) = (Some("foo"), None); /// tuples.expect("will panic"); /// ``` fn expect(self, msg: &str) -> Self::Tuple { self.transpose().expect(msg) } /// See [`Option::unwrap`]. /// ``` /// # use tuple_combinator::TupleCombinator; /// let tuples = (Some("foo"), Some(123)); /// assert_eq!(tuples.unwrap(), ("foo", 123)); /// ``` /// /// This example will panic: /// /// ```{.should_panic} /// # use tuple_combinator::TupleCombinator; /// let tuples: (_, Option<i32>) = (Some("foo"), None); /// tuples.unwrap(); /// ``` fn unwrap(self) -> Self::Tuple { self.transpose().unwrap() } /// See [`Option::and`]. /// ``` /// # use tuple_combinator::TupleCombinator; /// let left = (Some("foo"), Some(123)); /// let right = Some(("bar", 456)); /// assert_eq!(left.and(right), right); /// /// let left_none = (None, Some(123)); /// assert_eq!(left_none.and(right), None); /// ``` fn and(self, optb: Option<Self::Tuple>) -> Option<Self::Tuple> { self.transpose().and(optb) } /// See [`Option::and_then`]. /// ``` /// # use tuple_combinator::TupleCombinator; /// let tuples = (Some("foobar"), Some(123)); /// assert_eq!(tuples.and_then(|(a, b)| Some(a.len() + b)), Some(129)); /// /// assert_eq!(tuples.and_then(|(a, b)| if b % 2 != 1 { Some(b) } else { None }), None); /// ``` fn and_then<U, F: FnOnce(Self::Tuple) -> Option<U>>(self, f: F) -> Option<U> { self.transpose().and_then(f) } /// See [`Option::filter`]. /// ``` /// # use tuple_combinator::TupleCombinator; /// let tuples = (Some("foobar"), Some(123)); /// assert_eq!(tuples.filter(|(a, b)| b % 2 == 1), Some(("foobar", 123))); /// assert_eq!(tuples.filter(|(a, b)| b % 2 != 1), None); /// ``` fn filter<P: FnOnce(&Self::Tuple) -> bool>(self, predicate: P) -> Option<Self::Tuple> { self.transpose().filter(predicate) } /// See [`Option::or`]. /// ``` /// # use tuple_combinator::TupleCombinator; /// let left = (Some("foo"), Some(123)); /// let right = Some(("bar", 456)); /// assert_eq!(left.or(right), left.transpose()); /// /// let left_none = (None, Some(123)); /// assert_eq!(left_none.or(right), right); /// ``` fn or(self, optb: Option<Self::Tuple>) -> Option<Self::Tuple> { self.transpose().or(optb) } /// See [`Option::or_else`]. /// ``` /// # use tuple_combinator::TupleCombinator; /// let left = (Some("foo"), Some(123)); /// let right = Some(("bar", 456)); /// assert_eq!(left.or_else(|| right), left.transpose()); /// assert_eq!((None, Some(456)).or_else(|| right), right); /// ``` fn or_else<F: FnOnce() -> Option<Self::Tuple>>(self, f: F) -> Option<Self::Tuple> { self.transpose().or_else(f) } /// See [`Option::xor`]. /// ``` /// # use tuple_combinator::TupleCombinator; /// let left = (Some("foo"), Some(123)); /// let right = Some(("bar", 456)); /// assert_eq!(left.xor(None), left.transpose()); /// assert_eq!(None.xor(left.transpose()), left.transpose()); /// assert_eq!(left.xor(right), None); /// ``` fn xor(self, optb: Option<Self::Tuple>) -> Option<Self::Tuple> { self.transpose().xor(optb) } } /// Reduce tuples of [`Option`]s into results of various form, act in comparable to the iterators. /// ``` /// use tuple_combinator::TupleReducer; /// /// let res = (Some(1), Some(5), Some("rust_tuple")).fold(0, |sum, item| { /// sum.and_then(|s| { /// if let Some(raw_i32) = item.downcast_ref::<Option<i32>>() { /// return raw_i32.as_ref() /// .and_then(|val| { /// Some(s + val) /// }); /// } /// /// if let Some(raw_str) = item.downcast_ref::<Option<&str>>() { /// return raw_str.as_ref() /// .and_then(|val| { /// Some(s + val.len() as i32) /// }); /// } /// /// Some(s) /// }) /// }); /// /// assert_eq!(res, Some(16)); /// ``` #[doc(inline)] pub trait TupleReducer: Sized { /// Fold the tuple to obtain a final outcome. Depending on the implementation of the handler /// function, the fold can behave differently on various option types or values. /// /// # Examples /// /// Reduce tuples of i32 options to the sum of the contained values: /// /// ```rust /// use tuple_combinator::TupleReducer; /// /// let res = (Some(17), Some(20)).fold(5, |sum, item| { /// sum.and_then(|s| { /// item.downcast_ref::<Option<i32>>() /// .and_then(|raw| raw.as_ref()) /// .and_then(|val| { /// Some(s + val) /// }) /// }) /// }); /// /// assert_eq!(res, Some(42)); /// ``` fn fold<U, F: Fn(Option<U>, &dyn Any) -> Option<U>>(&self, init: U, f: F) -> Option<U>; /// `fold_strict` works very much like `fold`, except that only options with the same wrapped data /// type as the output type will be "folded", i.e. invoking the supplied folding function. This /// function will come into handy when the caller only care about the options in the tuples that /// match the output type. /// /// # Examples /// ```rust /// use tuple_combinator::TupleReducer; /// /// let res = (Some(40), Some("noise"), None as Option<i32>, Some(2)) /// .fold_strict(0i32, |sum, item| { /// sum.and_then(|s| { /// Some(s + item) /// }) /// }); /// /// assert_eq!(res, Some(42)); /// ``` fn fold_strict<U: Any, F: Fn(Option<U>, &U) -> Option<U>>(&self, init: U, f: F) -> Option<U>; /// Convert the tuples to a reference slice, where caller can use native iteration tools. Note /// that this is re-export of the tuples' internal content, hence the slice can't live longer /// than the tuple self. /// /// # Examples /// /// ```rust /// use std::any::Any; /// use tuple_combinator::TupleReducer; /// /// let mut src = (Some(1), None as Option<&str>, Some(2), None as Option<i32>, Some(())); /// /// // convert the tuples to a slice of `Any` type /// let slice: Box<[&dyn Any]> = src.ref_slice(); /// /// // the slice has the same amount of elements as in the tuples. /// assert_eq!(slice.len(), 5); /// /// // downcast the element to its actual type; wrong type cast will be rejected with a `None` /// // output from the API call. /// assert_eq!(slice[0].downcast_ref::<Option<i32>>().unwrap(), &Some(1)); /// assert_eq!(slice[0].downcast_ref::<Option<&str>>(), None); /// assert_eq!(slice[1].downcast_ref::<Option<&str>>().unwrap(), &None); /// /// // unlike `mut_slice` API, the line below won't compile even if adding the `mut` keyword /// // to the `slice` variable, because the source slice is immutable. /// // let first = slice[0].downcast_mut::<Option<i32>>().unwrap().take(); /// ``` fn ref_slice(&self) -> Box<[&dyn Any]>; /// Convert the tuples to a reference slice which only include options wrapping the data of the /// desired type [`T`]. Options with types other than the given one will be excluded from the slice. /// Note that if the slice length is 0, it means the source tuple does not contain elements in /// options that can be converted to type ['T']. /// /// # Examples /// ```rust /// use tuple_combinator::TupleReducer; /// /// let src = (Some(1), None as Option<&str>, Some(2), None as Option<i32>, Some(())); /// let slice = src.strict_ref_slice::<i32>(); /// /// // The above variable initiation is equivalent to the following: /// // let slice: Box<[&i32]> = src.strict_ref_slice(); /// /// assert_eq!(slice.len(), 3); /// assert_eq!( /// slice, /// vec![&Some(1), &Some(2), &None as &Option<i32>].into_boxed_slice() /// ); /// /// // The line below won't compile because the immutability of the slice. /// // let first = slice[0].downcast_mut::<Option<i32>>().unwrap().take(); /// ``` fn strict_ref_slice<T: Any>(&self) -> Box<[&Option<T>]>; /// This method works similar to `ref_slice`, except that the members of the slice are mutable, /// such that it is possible to make updates, or taking ownership from the underlying tuples data. /// Note that modifying or altering the slice data will also cause the same data in the tuples to /// be altered. /// /// # Examples /// /// ```rust /// use std::any::Any; /// use tuple_combinator::TupleReducer; /// /// let mut src = (Some(1), None as Option<&str>, Some(2), None as Option<i32>, Some(())); /// let slice: Box<[&mut dyn Any]> = src.mut_slice(); /// /// assert_eq!(slice.len(), 5); /// assert_eq!(slice[0].downcast_ref::<Option<i32>>().unwrap(), &Some(1)); /// assert_eq!(slice[1].downcast_ref::<Option<&str>>().unwrap(), &None); /// /// let first = slice[0].downcast_mut::<Option<i32>>().unwrap().take(); /// assert_eq!(first, Some(1)); /// ``` fn mut_slice(&mut self) -> Box<[&mut dyn Any]>; /// This method works similar to `strict_ref_slice`, except that the members of the slice are /// mutable, such that it is possible to make updates, or taking ownership from the underlying /// tuples data. Note that modifying or altering the slice data will also cause the same data /// in the tuples to be altered. /// /// # Examples /// /// ```rust /// use tuple_combinator::TupleReducer; /// /// let mut src = (Some(1), None as Option<&str>, Some(2), None as Option<i32>, Some(())); /// let slice = src.strict_mut_slice::<i32>(); /// /// // The above variable initiation is equivalent to the following: /// // let slice: Box<[&mut i32]> = src.strict_mut_slice(); /// /// assert_eq!(slice.len(), 3); /// assert_eq!( /// slice, /// vec![&mut Some(1), &mut Some(2), &mut None as &mut Option<i32>].into_boxed_slice() /// ); /// /// // Now you can take the wrapped content out of the tuples/slice and operate on the element. /// // Note that operations on the slice element will take the same effect on the origin tuples, /// // since slice elements are merely mutable borrows. /// let first = slice[0].take(); /// assert_eq!(first, Some(1)); /// assert_eq!(slice[0], &mut None); /// ``` fn strict_mut_slice<T: Any>(&mut self) -> Box<[&mut Option<T>]>; } macro_rules! tuple_impls { ( $( $v:ident: $T:ident, )* ) => { impl<$($T,)*> TupleCombinator for ($(Option<$T>,)*) { type Tuple = ($($T,)*); fn transpose(self) -> Option<Self::Tuple> { if let ($(Some($v),)*) = self { Some(($($v,)*)) } else { None } } } }; } macro_rules! tuple_impl_reduce { () => {}; ( $( $ntyp:ident => $nidx:tt, )+ ) => { impl<$( $ntyp, )+> TupleReducer for ( $( Option<$ntyp>, )+ ) where $( $ntyp: Any, )* { fn fold<U, F: Fn(Option<U>, &dyn Any) -> Option<U>>(&self, init: U, f: F) -> Option<U> { let mut accu = Some(init); $( accu = f(accu, &self.$nidx); )* accu } fn fold_strict<U: Any, F: Fn(Option<U>, &U) -> Option<U>>(&self, init: U, f: F) -> Option<U> { let mut accu = Some(init); $( let opt = (&self.$nidx as &dyn Any) .downcast_ref::<Option<U>>() .and_then(|opt| opt.as_ref()); // avoid using combinator here since closure will cause `accu` to move and lead // to all sorts of headache. if let Some(value) = opt { accu = f(accu, value); } )* accu } fn ref_slice(&self) -> Box<[&dyn Any]> { // The maximum amount of elements in a tuple is 12, that's the upper-bound let mut vec: Vec<&dyn Any> = Vec::with_capacity(12); $( vec.push(&self.$nidx); )* vec.into_boxed_slice() } fn strict_ref_slice<T: Any>(&self) -> Box<[&Option<T>]> { // The maximum amount of elements in a tuple is 12, that's the upper-bound let mut vec: Vec<&Option<T>> = Vec::with_capacity(12); $( (&self.$nidx as &dyn Any) .downcast_ref::<Option<T>>() .and_then(|opt| { vec.push(opt); Some(()) }); )* vec.into_boxed_slice() } fn mut_slice(&mut self) -> Box<[&mut dyn Any]> { // The maximum amount of elements in a tuple is 12, that's the upper-bound let mut vec: Vec<&mut dyn Any> = Vec::with_capacity(12); $( vec.push(&mut self.$nidx); )* vec.into_boxed_slice() } fn strict_mut_slice<T: Any>(&mut self) -> Box<[&mut Option<T>]> { // The maximum amount of elements in a tuple is 12, that's the upper-bound let mut vec: Vec<&mut Option<T>> = Vec::with_capacity(12); $( (&mut self.$nidx as &mut dyn Any) .downcast_mut::<Option<T>>() .and_then(|opt| { vec.push(opt); Some(()) }); )* vec.into_boxed_slice() } } }; } // Impl TupleCombinator tuple_impls! { t1: T1, } tuple_impls! { t1: T1, t2: T2, } tuple_impls! { t1: T1, t2: T2, t3: T3, } tuple_impls! { t1: T1, t2: T2, t3: T3, t4: T4, } tuple_impls! { t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, } tuple_impls! { t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, } tuple_impls! { t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, } tuple_impls! { t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8, } tuple_impls! { t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8, t9: T9, } tuple_impls! { t1: T1, t2: T2, t3: T3, t4: T4, t5: T5, t6: T6, t7: T7, t8: T8, t9: T9, t10: T10, } // Impl TupleReducer tuple_impl_reduce! { T0 => 0, } tuple_impl_reduce! { T0 => 0, T1 => 1, } tuple_impl_reduce! { T0 => 0, T1 => 1, T2 => 2, } tuple_impl_reduce! { T0 => 0, T1 => 1, T2 => 2, T3 => 3, } tuple_impl_reduce! { T0 => 0, T1 => 1, T2 => 2, T3 => 3, T4 => 4, } tuple_impl_reduce! { T0 => 0, T1 => 1, T2 => 2, T3 => 3, T4 => 4, T5 => 5, } tuple_impl_reduce! { T0 => 0, T1 => 1, T2 => 2, T3 => 3, T4 => 4, T5 => 5, T6 => 6, } tuple_impl_reduce! { T0 => 0, T1 => 1, T2 => 2, T3 => 3, T4 => 4, T5 => 5, T6 => 6, T7 => 7, } tuple_impl_reduce! { T0 => 0, T1 => 1, T2 => 2, T3 => 3, T4 => 4, T5 => 5, T6 => 6, T7 => 7, T8 => 8, } tuple_impl_reduce! { T0 => 0, T1 => 1, T2 => 2, T3 => 3, T4 => 4, T5 => 5, T6 => 6, T7 => 7, T8 => 8, T9 => 9, } #[cfg(test)] mod impl_tests { use super::TupleReducer; use std::any::Any; #[test] fn fold_sum() { let res = (Some(17), Some(20)).fold(5, |sum, item| { sum.and_then(|s| { item.downcast_ref::<Option<i32>>() .and_then(|raw| raw.as_ref()) .and_then(|val| Some(s + val)) }) }); assert_eq!(res, Some(42)); } #[test] fn fold_mixed() { let res = ( Some(1), Some(5), Some("rust_tuple"), Some(String::from("tuple_reducer")), Some(vec![0u8, 1, 42]), // the vec that wraps all the wisdom of this universe ).fold(0, |sum, item| { sum.and_then(|s| { if let Some(raw_i32) = item.downcast_ref::<Option<i32>>() { return raw_i32.as_ref().and_then(|val| Some(s + val)); } if let Some(raw_str) = item.downcast_ref::<Option<&str>>() { return raw_str.as_ref().and_then(|val| Some(s + val.len() as i32)); } if let Some(raw_string) = item.downcast_ref::<Option<String>>() { return raw_string.as_ref().and_then(|val| Some(s + val.len() as i32)); } if let Some(raw_vec) = item.downcast_ref::<Option<Vec<u8>>>() { return raw_vec.as_ref().and_then(|val| Some(s + val.len() as i32)); } Some(s) }) }); assert_eq!(res, Some(32)); } #[test] fn fold_none_as_nuke() { let none: Option<i32> = None; let res = (Some(1), none, Some(5)).fold(0, |sum, item| { sum.and_then(|s| { item.downcast_ref::<Option<i32>>() .and_then(|raw| raw.as_ref()) .and_then(|val| Some(s + val)) }) }); assert_eq!(res, None); } #[test] fn fold_none_as_reset() { let none: Option<i32> = None; let init = 0; let res = (Some(1), none, Some(5)).fold(init, |sum, item| { item.downcast_ref::<Option<i32>>() .and_then(|raw| raw.as_ref()) .and_then(|val| { if let Some(s) = sum { Some(s + val) } else { Some(init + val) } }) }); assert_eq!(res, Some(5)); } #[test] fn fold_strict_base() { let res = (Some(40), Some("noise"), None as Option<i32>, Some(2)) .fold_strict(0i32, |sum, item| { sum.and_then(|s| { Some(s + item) }) }); assert_eq!(res, Some(42)); } #[test] fn ref_slice_base() { let src = (Some(1), None as Option<&str>, Some(2), None as Option<i32>, Some(())); // convert the tuples to a slice of `Any` type let slice: Box<[&dyn Any]> = src.ref_slice(); // the slice has the same amount of elements as in the tuples. assert_eq!(slice.len(), 5); // downcast the element to its actual type; wrong type cast will be rejected with a `None` // output from the API call. assert_eq!(slice[0].downcast_ref::<Option<i32>>().unwrap(), &Some(1)); assert_eq!(slice[0].downcast_ref::<Option<&str>>(), None); assert_eq!(slice[1].downcast_ref::<Option<&str>>().unwrap(), &None); } #[test] fn strict_ref_slice_base() { let src = (Some(1), None as Option<&str>, Some(2), None as Option<i32>, Some(())); let slice = src.strict_ref_slice::<i32>(); // The above variable initiation is equivalent to the following: // let slice: Box<[&i32]> = src.strict_ref_slice(); assert_eq!(slice.len(), 3); assert_eq!( slice, vec![&Some(1), &Some(2), &None as &Option<i32>].into_boxed_slice() ); } #[test] fn mut_slice_base() { let mut src = (Some(1), None as Option<&str>, Some(2), None as Option<i32>, Some(())); let slice: Box<[&mut dyn Any]> = src.mut_slice(); assert_eq!(slice.len(), 5); assert_eq!(slice[0].downcast_ref::<Option<i32>>().unwrap(), &Some(1)); assert_eq!(slice[1].downcast_ref::<Option<&str>>().unwrap(), &None); let first = slice[0].downcast_mut::<Option<i32>>().unwrap().take(); assert_eq!(first, Some(1)); } #[test] fn strict_mut_slice_base() { let mut src = (Some(1), None as Option<&str>, Some(2), None as Option<i32>, Some(())); let slice = src.strict_mut_slice::<i32>(); // The above variable initiation is equivalent to the following: // let slice: Box<[&mut i32]> = src.strict_mut_slice(); assert_eq!(slice.len(), 3); assert_eq!( slice, vec![&mut Some(1), &mut Some(2), &mut None as &mut Option<i32>].into_boxed_slice() ); let first = slice[0].take(); assert_eq!(first, Some(1)); assert_eq!(slice[0], &mut None); } }