Trait Pipe

pub trait Pipe {
    // Provided methods
    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 { ... }
}

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

fn pipe<R>(self, func: impl FnOnce(Self) -> R) -> R

where Self: Sized, R: Sized,

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,
);

fn pipe_ref<'a, R>(&'a self, func: impl FnOnce(&'a Self) -> R) -> R

where R: 'a + Sized,

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);

fn pipe_ref_mut<'a, R>(&'a mut self, func: impl FnOnce(&'a mut Self) -> R) -> R

where R: 'a + Sized,

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.

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,

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);

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,

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.

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,

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

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,

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

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,

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

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,

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

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl<T> Pipe for T

where T: ?Sized,