vendor/generic-array-0.12.3/src/functional.rs

   1 //! Functional programming with generic sequences
   2 //!
   3 //! Please see `tests/generics.rs` for examples of how to best use these in your generic functions.
   4
   5 use super::ArrayLength;
   6 use core::iter::FromIterator;
   7 use sequence::*;
   8
   9 /// Defines the relationship between one generic sequence and another,
  10 /// for operations such as `map` and `zip`.
  11 pub unsafe trait MappedGenericSequence<T, U>: GenericSequence<T>
  12 where
  13     Self::Length: ArrayLength<U>,
  14 {
  15     /// Mapped sequence type
  16     type Mapped: GenericSequence<U, Length = Self::Length>;
  17 }
  18
  19 unsafe impl<'a, T, U, S: MappedGenericSequence<T, U>> MappedGenericSequence<T, U> for &'a S
  20 where
  21     &'a S: GenericSequence<T>,
  22     S: GenericSequence<T, Length = <&'a S as GenericSequence<T>>::Length>,
  23     <S as GenericSequence<T>>::Length: ArrayLength<U>,
  24 {
  25     type Mapped = <S as MappedGenericSequence<T, U>>::Mapped;
  26 }
  27
  28 unsafe impl<'a, T, U, S: MappedGenericSequence<T, U>> MappedGenericSequence<T, U> for &'a mut S
  29 where
  30     &'a mut S: GenericSequence<T>,
  31     S: GenericSequence<T, Length = <&'a mut S as GenericSequence<T>>::Length>,
  32     <S as GenericSequence<T>>::Length: ArrayLength<U>,
  33 {
  34     type Mapped = <S as MappedGenericSequence<T, U>>::Mapped;
  35 }
  36
  37 /// Accessor type for a mapped generic sequence
  38 pub type MappedSequence<S, T, U> =
  39     <<S as MappedGenericSequence<T, U>>::Mapped as GenericSequence<U>>::Sequence;
  40
  41 /// Defines functional programming methods for generic sequences
  42 pub unsafe trait FunctionalSequence<T>: GenericSequence<T> {
  43     /// Maps a `GenericSequence` to another `GenericSequence`.
  44     ///
  45     /// If the mapping function panics, any already initialized elements in the new sequence
  46     /// will be dropped, AND any unused elements in the source sequence will also be dropped.
  47     fn map<U, F>(self, f: F) -> MappedSequence<Self, T, U>
  48     where
  49         Self: MappedGenericSequence<T, U>,
  50         Self::Length: ArrayLength<U>,
  51         F: FnMut(Self::Item) -> U,
  52     {
  53         FromIterator::from_iter(self.into_iter().map(f))
  54     }
  55
  56     /// Combines two `GenericSequence` instances and iterates through both of them,
  57     /// initializing a new `GenericSequence` with the result of the zipped mapping function.
  58     ///
  59     /// If the mapping function panics, any already initialized elements in the new sequence
  60     /// will be dropped, AND any unused elements in the source sequences will also be dropped.
  61     #[inline]
  62     fn zip<B, Rhs, U, F>(self, rhs: Rhs, f: F) -> MappedSequence<Self, T, U>
  63     where
  64         Self: MappedGenericSequence<T, U>,
  65         Rhs: MappedGenericSequence<B, U, Mapped = MappedSequence<Self, T, U>>,
  66         Self::Length: ArrayLength<B> + ArrayLength<U>,
  67         Rhs: GenericSequence<B, Length = Self::Length>,
  68         F: FnMut(Self::Item, Rhs::Item) -> U,
  69     {
  70         rhs.inverted_zip2(self, f)
  71     }
  72
  73     /// Folds (or reduces) a sequence of data into a single value.
  74     ///
  75     /// If the fold function panics, any unused elements will be dropped.
  76     fn fold<U, F>(self, init: U, f: F) -> U
  77     where
  78         F: FnMut(U, Self::Item) -> U,
  79     {
  80         self.into_iter().fold(init, f)
  81     }
  82 }
  83
  84 unsafe impl<'a, T, S: GenericSequence<T>> FunctionalSequence<T> for &'a S
  85 where
  86     &'a S: GenericSequence<T>,
  87 {
  88 }
  89
  90 unsafe impl<'a, T, S: GenericSequence<T>> FunctionalSequence<T> for &'a mut S
  91 where
  92     &'a mut S: GenericSequence<T>,
  93 {
  94 }