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use core::marker::PhantomData;
use core::ops::Deref;
use curry2::Curry2;
use curry3::Curry3;
use self::compose::Compose;
/// Function composition
pub mod compose;
/// Currying functions with 2 arguments
pub mod curry2;
/// Currying functions with 3 arguments
pub mod curry3;
/// Create a tuple
///
/// ```
/// use naan::prelude::*;
///
/// let a = Some("a");
/// let b = Some(2);
///
/// let tup: Option<(&'static str, usize)> = a.and_then(|a| b.map(|b| (a, b)));
/// let tup: Option<(&'static str, usize)> = Some(tuple2.curry()).apply1(a).apply1(b);
/// ```
pub fn tuple2<A, B>(a: A, b: B) -> (A, B) {
(a, b)
}
/// Create a 3-tuple
///
/// ```
/// use naan::prelude::*;
///
/// let a = Some("a");
/// let b = Some(2);
/// let c = Some([1, 2, 3]);
///
/// let tup: Option<(&'static str, usize, [usize; 3])> =
/// a.and_then(|a| b.and_then(|b| c.map(|c| (a, b, c))));
/// let tup: Option<(&'static str, usize, [usize; 3])> =
/// Some(tuple3.curry()).apply1(a).apply1(b).apply1(c);
/// ```
pub fn tuple3<A, B, C>(a: A, b: B, c: C) -> (A, B, C) {
(a, b, c)
}
pub(self) mod arg {
#[allow(unreachable_pub)]
pub trait Arg {
/// The type of the argument
type T;
}
}
/// Type-level marker indicating that the curried function has been applied with this argument
#[derive(Clone, Copy)]
pub struct Just<T>(/// The argument
pub T);
/// Type-level marker indicating that the curried function has **not** been applied with this argument
pub struct Nothing<T>(pub(self) PhantomData<T>);
impl<T> Nothing<T> {
/// Create a Nothing
pub fn new() -> Self {
Self(PhantomData)
}
}
impl<T> Default for Nothing<T> {
fn default() -> Self {
Self::new()
}
}
impl<T> Clone for Nothing<T> {
fn clone(&self) -> Self {
Self::new()
}
}
impl<T> arg::Arg for Just<T> {
type T = T;
}
impl<T> arg::Arg for Nothing<T> {
type T = T;
}
/// Type of [`fn@call_deref`]
#[allow(non_camel_case_types)]
pub type call_deref<F, A, B> = fn(f: F, a: A) -> B;
/// Lift a function from `&ADeref -> B` to `A -> B`
/// where `A` can [`Deref::deref`] as `ADeref`
///
/// Used by [`F1Once::chain_ref`].
pub fn call_deref<F, A, ADeref: ?Sized, B>(f: F, a: A) -> B
where A: Deref<Target = ADeref>,
F: for<'a> F1Once<&'a ADeref, Ret = B>
{
f.call1(a.deref())
}
/// A function that accepts 1 argument
/// and can be called at most once.
pub trait F1Once<A> {
/// The type returned by this function
type Ret;
/// Call the function
fn call1(self, a: A) -> Self::Ret;
/// Create a new function that passes this one's output to `g`'s input
///
/// (Left-to-right function composition)
///
/// ```no_run
/// use std::path::{Path, PathBuf};
///
/// use naan::prelude::*;
///
/// fn ensure_trailing_slash(s: &str) -> String {
/// if !s.ends_with("/") {
/// format!("{s}/")
/// } else {
/// s.into()
/// }
/// }
///
/// fn main() {
/// let dir_contains_readme = ensure_trailing_slash.chain(|path| format!("{path}README.md"))
/// .chain(PathBuf::from)
/// .chain_ref(Path::exists);
///
/// assert!(dir_contains_readme.call("toad-lib/toad/toad"));
/// assert!(!dir_contains_readme.call("toad-lib/toad"));
/// }
/// ```
///
/// ## A Note on Type Errors
/// TLDR: try `chain_ref` if the function is a receiver of `&self` or a similar shape,
/// and if that fails wrap the composed function with `Box::new(...) as Box<dyn F1<.., ..>>`
/// for more valuable compiler errors.
///
/// <details>
///
/// The type errors from chained composition type errors tend to be very complex.
///
/// While debugging type errors like this, it may help to use `Box<dyn F1>` to
/// provide more type information to the compiler, e.g.
///
/// ```compile_fail
/// use std::path::{Path, PathBuf};
///
/// use naan::prelude::*;
///
/// fn ensure_trailing_slash(s: &str) -> String {
/// if !s.ends_with("/") {
/// format!("{s}/")
/// } else {
/// s.into()
/// }
/// }
///
/// fn main() {
/// let dir_contains_readme =
/// ensure_trailing_slash.chain(|path| format!("{path}README.md")).chain(PathBuf::from)
/// .chain(Path::exists);
///
/// assert!(dir_contains_readme.call("toad-lib/toad/toad"));
/// }
/// ```
/// produces type error:
/// ```text
/// error[E0599]: the method `call1` exists for struct `Compose<Compose<Compose<..>, ..>, .., ..>`, but its trait bounds were not satisfied
/// --> src/fun/mod.rs:37:31
/// |
/// 19 | assert!(dir_contains_readme.call1("toad-lib/toad/toad"));
/// | ^^^^^ method cannot be called on `Compose<Compose<Compose<..>, ..>, .., ..>` due to unsatisfied trait bounds
/// ```
///
/// when we box it, the compiler much more helpfully tells us that the issue is that `Path::exists` is `&Path -> bool`, rather than `PathBuf -> bool`:
///
/// ```compile_fail
/// # use std::path::{Path, PathBuf};
/// # use naan::prelude::*;
/// # fn ensure_trailing_slash(s: &str) -> String {
/// # if !s.ends_with("/") {
/// # format!("{s}/")
/// # } else {
/// # s.into()
/// # }
/// # }
/// fn main() {
/// let dir_contains_readme =
/// ensure_trailing_slash.chain(|path| format!("{path}README.md")).chain(PathBuf::from)
/// .chain(Path::exists);
///
/// let dir_contains_readme_boxed: Box<dyn F1<&str, Ret = bool>> = Box::new(dir_contains_readme) as _;
///
/// assert!(dir_contains_readme_boxed.call("toad-lib/toad/toad"));
/// }
/// ```
/// yields
/// ```text
/// error[E0631]: type mismatch in function arguments
/// --> src/fun/compose.rs:91:75
/// |
/// 17 | ... .chain(Path::exists);
/// | ----- ^^^^^^^^^^^^
/// | | |
/// | | expected due to this
/// | | found signature defined here
/// | required by a bound introduced by this call
/// |
/// = note: expected function signature `fn(PathBuf) -> _`
/// found function signature `for<'r> fn(&'r Path) -> _`
/// = note: required for `for<'r> fn(&'r Path) -> bool {Path::exists}` to implement `F1Once<PathBuf, _>`
/// ```
/// Once all type errors are resolved, the Box debugging can be undone and you can use the concrete
/// nested `Compose` types.
/// </details>
fn chain<G, C>(self, g: G) -> Compose<Self, G, Self::Ret>
where Self: Sized,
G: F1Once<Self::Ret, Ret = C>
{
Compose::compose(self, g)
}
/// [`chain`](F1Once::chain) that passes a reference to this function's return type
/// to function `g`.
///
/// Also performs [`Deref::deref`], allowing you to do things like pipe a `Vec`
/// to a function expecting a slice or `String` to a function expecting `&str`.
fn chain_ref<G, BDeref: ?Sized, C>(
self,
g: G)
-> Compose<Self, curry2::Applied1<call_deref<G, Self::Ret, C>, G, Self::Ret, C>, Self::Ret>
where Self: Sized,
G: for<'any> F1Once<&'any BDeref, Ret = C>,
Self::Ret: Deref<Target = BDeref>
{
Compose::compose(self,
(call_deref as call_deref<G, Self::Ret, C>).curry().call(g))
}
}
/// A function that accepts 2 arguments
/// and can be called at most once.
pub trait F2Once<A, B>: Sized {
/// The type returned by this function
type Ret;
/// The concrete type that `curry` returns.
type Curried;
/// Call the function
fn call1(self, a: A, b: B) -> Self::Ret;
/// Curry this function, transforming it from
/// `fn(A, B) -> C` to `fn(A) -> fn(B) -> C`
fn curry(self) -> Self::Curried;
}
/// A function that accepts 3 arguments
/// and can be called at most once.
pub trait F3Once<A, B, C>: Sized {
/// The type returned by this function
type Ret;
/// The concrete type that `curry` returns.
type Curried;
/// Call the function
fn call1(self, a: A, b: B, c: C) -> Self::Ret;
/// Curry this function, transforming it from
/// `fn(A, B, C) -> D` to `fn(A) -> fn(B) -> fn(C) -> Self::Ret`
fn curry(self) -> Self::Curried;
}
/// A function that accepts 1 argument
/// and can be called any number of times.
pub trait F1<A>: F1Once<A> {
/// Call the function
fn call(&self, a: A) -> Self::Ret;
}
/// A function that accepts 2 arguments
/// and can be called any number of times.
pub trait F2<A, B>: F2Once<A, B> {
/// Call the function with all arguments
fn call(&self, a: A, b: B) -> Self::Ret;
}
/// A function that accepts 3 arguments
/// and can be called any number of times.
pub trait F3<A, B, C>: F3Once<A, B, C> {
/// Call the function with all arguments
fn call(&self, a: A, b: B, c: C) -> Self::Ret;
}
impl<F, A, B> F1<A> for F where F: Fn(A) -> B
{
fn call(&self, a: A) -> B {
self(a)
}
}
impl<F, A, B> F1Once<A> for F where F: FnOnce(A) -> B
{
type Ret = B;
fn call1(self, a: A) -> B {
self(a)
}
}
impl<F, A, B, C> F2<A, B> for F where F: Fn(A, B) -> C
{
fn call(&self, a: A, b: B) -> Self::Ret {
self(a, b)
}
}
impl<F, A, B, C> F2Once<A, B> for F where F: FnOnce(A, B) -> C
{
type Ret = C;
type Curried = curry2::Applied0<Self, A, B, C>;
fn call1(self, a: A, b: B) -> C {
self(a, b)
}
fn curry(self) -> Self::Curried {
Curry2::curry(self)
}
}
impl<F, A, B, C, D> F3<A, B, C> for F where F: Fn(A, B, C) -> D
{
fn call(&self, a: A, b: B, c: C) -> D {
self(a, b, c)
}
}
impl<F, A, B, C, D> F3Once<A, B, C> for F where F: FnOnce(A, B, C) -> D
{
type Ret = D;
type Curried = curry3::Applied0<Self, A, B, C, D>;
fn call1(self, a: A, b: B, c: C) -> D {
self(a, b, c)
}
fn curry(self) -> Self::Curried {
Curry3::curry(self)
}
}