Trait tap::Pipe

source · [−]
pub trait Pipe {
    fn pipe<R>(self, func: impl FnOnce(Self) -> R) -> R
    where
        Self: Sized,
        R: Sized,
    { ... }

    fn pipe_ref<'a, R>(&'a self, func: impl FnOnce(&'a Self) -> R) -> R
    where
        R: 'a + Sized,
    { ... }

    fn pipe_ref_mut<'a, R>(
        &'a mut self, 
        func: impl FnOnce(&'a mut Self) -> R
    ) -> R
    where
        R: 'a + Sized,
    { ... }

    fn pipe_borrow<'a, B, R>(&'a self, func: impl FnOnce(&'a B) -> R) -> R
    where
        Self: Borrow<B>,
        B: 'a + ?Sized,
        R: 'a + Sized,
    { ... }

    fn pipe_borrow_mut<'a, B, R>(
        &'a mut self, 
        func: impl FnOnce(&'a mut B) -> R
    ) -> R
    where
        Self: BorrowMut<B>,
        B: 'a + ?Sized,
        R: 'a + Sized,
    { ... }

    fn pipe_as_ref<'a, U, R>(&'a self, func: impl FnOnce(&'a U) -> R) -> R
    where
        Self: AsRef<U>,
        U: 'a + ?Sized,
        R: 'a + Sized,
    { ... }

    fn pipe_as_mut<'a, U, R>(
        &'a mut self, 
        func: impl FnOnce(&'a mut U) -> R
    ) -> R
    where
        Self: AsMut<U>,
        U: 'a + ?Sized,
        R: 'a + Sized,
    { ... }

    fn pipe_deref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R
    where
        Self: Deref<Target = T>,
        T: 'a + ?Sized,
        R: 'a + Sized,
    { ... }

    fn pipe_deref_mut<'a, T, R>(
        &'a mut self, 
        func: impl FnOnce(&'a mut T) -> R
    ) -> R
    where
        Self: DerefMut + Deref<Target = T>,
        T: 'a + ?Sized,
        R: 'a + Sized,
    { ... }
}
Expand description

Provides universal suffix-position call syntax for any function.

This trait provides methods that allow any closure or free function to be placed as a suffix-position call, by writing them as

fn not_a_method(x: i32) -> u8 { x as u8 }
receiver.pipe(not_a_method);

Piping into functions that take more than one argument still requires writing a closure with ordinary function-call syntax. This is after all only a library, not a syntax transformation:

use tap::pipe::Pipe;
fn add(x: i32, y: i32) -> i32 { x + y }

let out = 5.pipe(|x| add(x, 10));
assert_eq!(out, 15);

Like tapping, piping is useful for cases where you want to write a sequence of processing steps without introducing many intermediate bindings, and your steps contain functions which are not eligible for dot-call syntax.

The main difference between piping and tapping is that tapping always returns the value that was passed into the tap, while piping forwards the value into the effect function, and returns the output of evaluating the effect function with the value. Piping is a transformation, not merely an inspection or modification.

Provided methods

Pipes by value. This is generally the method you want to use.

Examples
use tap::pipe::Pipe;

fn triple(x: i32) -> i64 {
  x as i64 * 3
}

assert_eq!(
  10.pipe(triple),
  30,
);

Borrows self and passes that borrow into the pipe function.

Examples
use tap::pipe::Pipe;

fn fold(v: &Vec<i32>) -> i32 {
  v.iter().copied().sum()
}
let vec = vec![1, 2, 3, 4, 5];
let sum = vec.pipe_ref(fold);
assert_eq!(sum, 15);
assert_eq!(vec.len(), 5);

Mutably borrows self and passes that borrow into the pipe function.

Examples
use tap::pipe::Pipe;

let mut vec = vec![false, true];
let last = vec
  .pipe_ref_mut(Vec::pop)
  .pipe(Option::unwrap);
assert!(last);

Both of these functions are eligible for method-call syntax, and should not be piped. Writing out non-trivial examples for these is a lot of boilerplate.

Borrows self, then passes self.borrow() into the pipe function.

Examples
use std::borrow::Cow;
use tap::pipe::Pipe;

let len = Cow::<'static, str>::from("hello, world")
  .pipe_borrow(str::len);
assert_eq!(len, 12);

Mutably borrows self, then passes self.borrow_mut() into the pipe function.

use tap::pipe::Pipe;

let mut txt = "hello, world".to_string();
let ptr = txt
  .pipe_borrow_mut(str::as_mut_ptr);

This is a very contrived example, but the BorrowMut trait has almost no implementors in the standard library, and of the implementations available, there are almost no methods that fit this API.

Borrows self, then passes self.as_ref() into the pipe function.

Mutably borrows self, then passes self.as_mut() into the pipe function.

Borrows self, then passes self.deref() into the pipe function.

Mutably borrows self, then passes self.deref_mut() into the pipe function.

Implementors