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//! A simple crate exposing tapping functionality for all types, and extended functionality for `Option`, `Result` & `Future`. //! //! The tap operation takes, and then returns, full ownership of the variable being tapped. //! This means that the closure may have mutable access to the variable, even if the variable is otherwise immutable. //! //! # Examples //! //! Logging error values: //! //! ```rust //! # use tap::*; //! let values: [Result<i32, &str>; 4] = [Ok(3), Err("foo"), Err("bar"), Ok(8)]; //! //! let _ = values.iter().filter_map(|result| //! // print error information before discarding them //! result.tap_err(|error| eprintln!("Invalid entry: {}", error)).ok() //! ); //! ``` //! //! Chaining methods: //! //! ```rust //! # use tap::*; //! fn get_numbers() -> Vec<u32> { //! vec![4, 9, 1, 17, 3] //! } //! //! let mut old = get_numbers(); //! old.sort(); //! //! // can now be written like this instead //! let new = get_numbers().tap(|data| data.sort()); //! //! assert_eq!(old, new) //! ``` //! //! Reducing the amount of mutable variables: //! //! ```rust //! # use tap::*; //! let tapped = [1, 2, 3]; // does not need to be mutable, preventing accidental mutations //! let tapped = tapped.tap(|arr| { //! for elt in arr.iter_mut() { //! *elt *= 2; //! } //! }); //! //! // instead of //! let mut untapped = [1, 2, 3]; //! for elt in untapped.iter_mut() { //! *elt *= 2; //! } //! assert_eq!(tapped, untapped); //! ``` #[cfg(feature = "future")] pub use self::future::TapFutureOps; #[cfg(feature = "future")] mod future; #[cfg(feature = "nom3")] pub use self::nom::TapNomOps; #[cfg(feature = "nom3")] mod nom; /// Tap operations for `bool`. pub trait TapBooleanOps { /// Executes a closure if `self` is `true`. /// /// # Examples /// /// ```rust /// # use tap::*; /// let mut foo = 0; /// let boolean = false; /// assert_eq!(boolean.tap_true(|| foo += 5), false); /// assert_eq!(foo, 0); /// ``` /// /// ```rust /// # use tap::*; /// let mut foo = 0; /// let boolean = true; /// assert_eq!(boolean.tap_true(|| foo += 5), true); /// assert_eq!(foo, 5); /// ``` fn tap_true<R, F: FnOnce() -> R>(self, f: F) -> Self; /// Executes a closure if `self` is `false`. /// /// # Examples /// /// ```rust /// # use tap::*; /// let mut foo = 0; /// let boolean = false; /// assert_eq!(boolean.tap_false(|| foo += 5), false); /// assert_eq!(foo, 5); /// ``` /// /// ```rust /// # use tap::*; /// let mut foo = 0; /// let boolean = true; /// assert_eq!(boolean.tap_false(|| foo += 5), true); /// assert_eq!(foo, 0); /// ``` fn tap_false<R, F: FnOnce() -> R>(self, f: F) -> Self; } impl TapBooleanOps for bool { fn tap_true<R, F: FnOnce() -> R>(self, f: F) -> Self { if self { let _ = f(); } self } fn tap_false<R, F: FnOnce() -> R>(self, f: F) -> Self { if !self { let _ = f(); } self } } /// Tap operations for `Result`. pub trait TapResultOps<T, E> { /// Executes a closure if the value is `Result::Ok(T)`. /// /// # Examples /// /// ```rust /// # use tap::*; /// let mut foo = 0; /// let res: Result<u32, u32> = Ok(4); /// assert_eq!(res.tap_ok(|&mut v| foo += v), Ok(4)); /// assert_eq!(foo, 4); /// ``` /// /// ```rust /// # use tap::*; /// let mut foo = 0; /// let res: Result<u32, u32> = Err(4); /// assert_eq!(res.tap_ok(|&mut v| foo += v), Err(4)); /// assert_eq!(foo, 0); /// ``` fn tap_ok<R, F: FnOnce(&mut T) -> R>(self, f: F) -> Self; /// Executes a closure if the value is `Result::Err(E)`. /// /// # Examples /// /// ```rust /// # use tap::*; /// let mut foo = 0; /// let res: Result<u32, u32> = Ok(4); /// assert_eq!(res.tap_err(|&mut v| foo += v), Ok(4)); /// assert_eq!(foo, 0); /// ``` /// /// ```rust /// # use tap::*; /// let mut foo = 0; /// let res: Result<u32, u32> = Err(4); /// assert_eq!(res.tap_err(|&mut v| foo += v), Err(4)); /// assert_eq!(foo, 4); /// ``` fn tap_err<R, F: FnOnce(&mut E) -> R>(self, f: F) -> Self; } impl<T, E> TapResultOps<T, E> for Result<T, E> { fn tap_ok<R, F: FnOnce(&mut T) -> R>(mut self, f: F) -> Self { if let Ok(mut val) = self.as_mut() { let _ = f(&mut val); } self } fn tap_err<R, F: FnOnce(&mut E) -> R>(mut self, f: F) -> Self { if let Err(mut val) = self.as_mut() { let _ = f(&mut val); } self } } /// Tap operations for `Option`. pub trait TapOptionOps<T> { /// Executes a closure if the value is `Option::Some(T)`. /// /// # Examples /// /// ```rust /// # use tap::*; /// let mut foo = 0; /// let res: Option<u32> = Some(4); /// assert_eq!(res.tap_some(|&mut v| foo += v), Some(4)); /// assert_eq!(foo, 4); /// ``` /// /// ```rust /// # use tap::*; /// let mut foo = 0; /// let res: Option<u32> = None; /// assert_eq!(res.tap_some(|&mut v| foo += v), None); /// assert_eq!(foo, 0); /// ``` fn tap_some<R, F: FnOnce(&mut T) -> R>(self, f: F) -> Self; /// Executes a closure if the value is `Option::None`. /// /// # Examples /// /// ```rust /// # use tap::*; /// let mut foo = 0; /// let res: Option<u32> = Some(4); /// assert_eq!(res.tap_none(|| foo += 5), Some(4)); /// assert_eq!(foo, 0); /// ``` /// /// ```rust /// # use tap::*; /// let mut foo = 0; /// let res: Option<u32> = None; /// assert_eq!(res.tap_none(|| foo += 5), None); /// assert_eq!(foo, 5); /// ``` fn tap_none<R, F: FnOnce() -> R>(self, f: F) -> Self; } impl<T> TapOptionOps<T> for Option<T> { fn tap_some<R, F: FnOnce(&mut T) -> R>(mut self, f: F) -> Self { if let Some(val) = self.as_mut() { let _ = f(val); } self } fn tap_none<R, F: FnOnce() -> R>(self, f: F) -> Self { if self.is_none() { let _ = f(); } self } } /// Tap operations for all types. pub trait TapOps: Sized { /// Executes a closure on an object, discarding the result. /// /// # Examples /// /// ```rust /// # use tap::*; /// let mut max = 0; /// let data: [u32; 5] = [2, 8, 3, 4, 0]; /// assert_eq!( /// data.tap(|x| x.sort()).tap(|x| max += x.last().unwrap()), /// [0, 2, 3, 4, 8] /// ); /// assert_eq!(max, 8); /// ``` fn tap<R, F>(self, f: F) -> Self where F: FnOnce(&mut Self) -> R; } impl<T> TapOps for T where T: Sized { fn tap<R, F>(mut self, f: F) -> Self where F: FnOnce(&mut Self) -> R { let _ = f(&mut self); self } }