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//! This module holds the machinery behind LabelledGeneric. //! //! A LabelledGeneric instance is pretty much exactly the same as a Generic instance, except //! that the generic representation should contain information about field names. //! //! Having a separate trait for LabelledGenerics gives us the freedom to derive both //! lablled and non-labelled generic type class instances for our types. //! //! Asides from the main LabelledGeneric trait, this module holds helper methods that allow //! users to use LabelledGeneric without using universal function call syntax. //! //! In addition, this module holds macro-generated enums that map to letters in field names (identifiers). //! //! # Examples //! //! ``` //! # #[macro_use] extern crate frunk_core; //! # use frunk_core::labelled::*; //! # use frunk_core::hlist::*; //! # fn main() { //! // Optionally alias our tuple that represents our type-level string //! type name = (n,a,m,e); //! let labelled = field![name, "Lloyd"]; //! assert_eq!(labelled.name, "name"); //! assert_eq!(labelled.value, "Lloyd") //! # } //! ``` //! //! A more common usage is to use LabelledGeneric to transform strucst that have mis-matched //! fields ! //! //! ``` //! # #[allow(unused_imports)] //! # #[macro_use] extern crate frunk_derives; //! # #[macro_use] extern crate frunk_core; //! # use frunk_core::hlist::*; fn main() { //! # use frunk_core::hlist::*; //! # use frunk_core::labelled::*; //! #[derive(LabelledGeneric)] //! struct NewUser<'a> { //! first_name: &'a str, //! last_name: &'a str, //! age: usize, //! } //! //! // Notice that the fields are mismatched in terms of ordering //! // *and* also in terms of the number of fields. //! #[derive(LabelledGeneric)] //! struct ShortUser<'a> { //! last_name: &'a str, //! first_name: &'a str, //! } //! //! let n_user = NewUser { //! first_name: "Joe", //! last_name: "Blow", //! age: 30, //! }; //! //! // transform_from automagically sculpts the labelled generic //! // representation of the source object to that of the target type //! let s_user: ShortUser = transform_from(n_user); // done //! # } //! ``` use std::marker::PhantomData; use hlist::*; use std::fmt; /// A trait that converts from a type to a labelled generic representation /// /// LabelledGenerics allow us to have completely type-safe, boilerplate free conversions /// between different structs. /// /// For the most part, you should be using the derivation that is available through /// frunk_derive to generate instances of this typeclass for your types. /// /// # Examples /// /// ```rust /// # #[allow(unused_imports)] /// # #[macro_use] extern crate frunk_derives; /// # #[macro_use] extern crate frunk_core; /// # use frunk_core::hlist::*; fn main() { /// use frunk_core::hlist::*; /// use frunk_core::labelled::*; /// #[derive(LabelledGeneric)] /// struct NewUser<'a> { /// first_name: &'a str, /// last_name: &'a str, /// age: usize, /// } /// /// // Notice that the fields are mismatched in terms of ordering /// #[derive(LabelledGeneric)] /// struct SavedUser<'a> { /// last_name: &'a str, /// age: usize, /// first_name: &'a str, /// } /// /// let n_user = NewUser { /// first_name: "Joe", /// last_name: "Blow", /// age: 30, /// }; /// /// // transform_from automagically sculpts the labelled generic /// // representation of the source object to that of the target type /// let s_user: SavedUser = transform_from(n_user); // done /// # } pub trait LabelledGeneric { /// The labelled generic representation type type Repr; /// Go from something to Repr fn into(self) -> Self::Repr; /// Go from labelled Repr to something fn from(r: Self::Repr) -> Self; /// From one type to another using a type with a compatible labelled generic representation fn convert_from<A>(a: A) -> Self where A: LabelledGeneric<Repr = Self::Repr>, Self: Sized, { let repr = <A as LabelledGeneric>::into(a); <Self as LabelledGeneric>::from(repr) } /// Converts from another type A into Self assuming that A and Self have labelled generic representations /// that can be sculpted into each other. /// /// Note that this method tosses away the "remainder" of the sculpted representation. In other /// words, anything that is not needed from A gets tossed out. #[deprecated = "obsolete, transform_from instead"] fn sculpted_convert_from<A, Indices>(a: A) -> Self where A: LabelledGeneric, Self: Sized, // The labelled representation of A must be sculpt-able into the labelled representation of Self <A as LabelledGeneric>::Repr: Sculptor<<Self as LabelledGeneric>::Repr, Indices>, { <Self as LabelledGeneric>::transform_from(a) } /// Converts from another type A into Self assuming that A and Self have labelled generic representations /// that can be sculpted into each other. /// /// Note that this method tosses away the "remainder" of the sculpted representation. In other /// words, anything that is not needed from A gets tossed out. fn transform_from<A, Indices>(a: A) -> Self where A: LabelledGeneric, Self: Sized, // The labelled representation of A must be sculpt-able into the labelled representation of Self <A as LabelledGeneric>::Repr: Sculptor<<Self as LabelledGeneric>::Repr, Indices>, { let a_gen = <A as LabelledGeneric>::into(a); // We toss away the remainder. let (self_gen, _): (<Self as LabelledGeneric>::Repr, _) = a_gen.sculpt(); <Self as LabelledGeneric>::from(self_gen) } } /// Given a labelled generic Representation of an A, returns A pub fn from_labelled_generic<A, Repr>(gen: Repr) -> A where A: LabelledGeneric<Repr = Repr>, { <A as LabelledGeneric>::from(gen) } /// Given an A, returns its labelled generic Representation pub fn into_labelled_generic<A, Repr>(a: A) -> Repr where A: LabelledGeneric<Repr = Repr>, { <A as LabelledGeneric>::into(a) } /// Converts one type into another assuming they have the same labelled generic Representation pub fn labelled_convert_from<A, B, Repr>(a: A) -> B where A: LabelledGeneric<Repr = Repr>, B: LabelledGeneric<Repr = Repr>, { <B as LabelledGeneric>::convert_from(a) } /// Converts from one type into another assuming that their labelled generic representations /// can be sculpted into each other. /// /// The "Indices" type parameter allows the compiler to figure out that the two representations /// can indeed be morphed into each other. #[deprecated = "obsolete, transform_from instead"] pub fn sculpted_convert_from<A, B, Indices>(a: A) -> B where A: LabelledGeneric, B: LabelledGeneric, // The labelled representation of A must be sculpt-able into the labelled representation of B <A as LabelledGeneric>::Repr: Sculptor<<B as LabelledGeneric>::Repr, Indices>, { <B as LabelledGeneric>::transform_from(a) } /// Converts from one type into another assuming that their labelled generic representations /// can be sculpted into each other. /// /// The "Indices" type parameter allows the compiler to figure out that the two representations /// can indeed be morphed into each other. pub fn transform_from<A, B, Indices>(a: A) -> B where A: LabelledGeneric, B: LabelledGeneric, // The labelled representation of A must be sculpt-able into the labelled representation of B <A as LabelledGeneric>::Repr: Sculptor<<B as LabelledGeneric>::Repr, Indices>, { <B as LabelledGeneric>::transform_from(a) } // Create a bunch of enums that can be used to represent characters on the type level macro_rules! create_enums_for { ($($i: ident)*) => { $( #[allow(non_snake_case, non_camel_case_types)] #[derive(PartialEq, Debug, Eq, Clone, Copy, PartialOrd, Ord, Hash)] pub enum $i {} )* } } // Add more as needed. create_enums_for! { a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z __ _1 _2 _3 _4 _5 _6 _7 _8 _9 _0 } /// A Label contains a type-level Name, a runtime value, and /// a reference to a `&'static str` name. /// /// To construct one, use the `field!` macro. /// /// # Examples /// /// ``` /// # #[macro_use] extern crate frunk_core; /// # use frunk_core::labelled::*; /// # use frunk_core::hlist::*; /// # fn main() { /// let labelled = field![(n,a,m,e), "joe"]; /// assert_eq!(labelled.name, "name"); /// assert_eq!(labelled.value, "joe") /// # } /// ``` #[cfg_attr(feature = "with_serde", derive(Serialize, Deserialize))] #[derive(PartialEq, Eq, Clone, Copy, PartialOrd, Ord, Hash)] pub struct Field<Name, Type> { name_type_holder: PhantomData<Name>, pub name: &'static str, pub value: Type, } /// A version of Field that doesn't have a type-level label, just a /// value-level one #[cfg_attr(feature = "with_serde", derive(Serialize, Deserialize))] #[derive(PartialEq, Eq, Clone, Copy, PartialOrd, Ord, Hash)] pub struct ValueField<Type> { pub name: &'static str, pub value: Type, } impl<Name, Type> fmt::Debug for Field<Name, Type> where Type: fmt::Debug, { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { let v_debug = format!("{:?}", self.value); write!(f, "Field{{ name: {}, value: {} }}", self.name, v_debug) } } impl<Type> fmt::Debug for ValueField<Type> where Type: fmt::Debug, { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { let v_debug = format!("{:?}", self.value); write!(f, "ValueField{{ name: {}, value: {} }}", self.name, v_debug) } } /// Returns a new Field for a given value and custom name. /// /// If you don't want to provide a custom name and want to rely on the type you provide /// to build a name, then please use the field! macro. /// /// # Examples /// /// ``` /// # use frunk_core::labelled::*; /// let l = field_with_name::<(n,a,m,e),_>("name", "joe"); /// assert_eq!(l.value, "joe"); /// assert_eq!(l.name, "name"); /// ``` pub fn field_with_name<Label, Value>(name: &'static str, value: Value) -> Field<Label, Value> { Field { name_type_holder: PhantomData, name: name, value: value, } } /// Trait for turning a Field HList into an un-labelled HList pub trait IntoUnlabelled { type Output; /// Turns the current HList into an unlabelled one. /// /// Effectively extracts the values held inside the individual Field /// /// # Examples /// /// ``` /// # #[macro_use] extern crate frunk_core; /// # use frunk_core::labelled::*; /// # use frunk_core::hlist::*; /// # fn main() { /// /// let labelled_hlist = hlist![ /// field!((n, a, m, e), "joe"), /// field!((a, g, e), 3) /// ]; /// /// let unlabelled = labelled_hlist.into_unlabelled(); /// /// assert_eq!(unlabelled, hlist!["joe", 3]) /// # } /// ``` fn into_unlabelled(self) -> Self::Output; } /// Implementation for HNil impl IntoUnlabelled for HNil { type Output = HNil; fn into_unlabelled(self) -> Self::Output { self } } /// Implementation when we have a non-empty HCons holding a label in its head impl<Label, Value, Tail> IntoUnlabelled for HCons<Field<Label, Value>, Tail> where Tail: IntoUnlabelled, { type Output = HCons<Value, <Tail as IntoUnlabelled>::Output>; fn into_unlabelled(self) -> Self::Output { HCons { head: self.head.value, tail: self.tail.into_unlabelled(), } } } /// Used for creating a Field /// /// There are 3 forms of this macro: /// /// * Create an instance of the `Field` struct with a tuple name type /// and any given value. The runtime-retrievable static name /// field will be set to the the concatenation of the types passed in the /// tuple type used as the first argument. /// /// # Examples /// /// ``` /// # #[macro_use] extern crate frunk_core; /// # use frunk_core::labelled::*; /// # use frunk_core::hlist::*; /// # fn main() { /// let labelled = field![(n,a,m,e), "joe"]; /// assert_eq!(labelled.name, "name"); /// assert_eq!(labelled.value, "joe") /// # } /// ``` /// /// * Create an instance of the `Field` struct with a custom, non-tuple /// name type and a value. The runtime-retrievable static name field /// will be set to the stringified version of the type provided. /// /// ``` /// # #[macro_use] extern crate frunk_core; /// # use frunk_core::labelled::*; /// # use frunk_core::hlist::*; /// # fn main() { /// enum first_name {} /// let labelled = field![first_name, "Joe"]; /// assert_eq!(labelled.name, "first_name"); /// assert_eq!(labelled.value, "Joe"); /// # } /// ``` /// /// * Create an instance of the `Field` struct with any name type and value, /// _and_ a custom name, passed as the last argument in the macro /// /// ``` /// # #[macro_use] extern crate frunk_core; /// # use frunk_core::labelled::*; /// # use frunk_core::hlist::*; /// # fn main() { /// // useful aliasing of our type-level string /// type age = (a, g, e); /// let labelled = field![age, 30, "Age"]; /// assert_eq!(labelled.name, "Age"); /// assert_eq!(labelled.value, 30); /// # } /// ``` #[macro_export] macro_rules! field { // No name provided and type is a tuple (($($repeated: ty),*), $value: expr) => { field!( ($($repeated),*), $value, concat!( $(stringify!($repeated)),* ) ) }; // No name provided and type is a tuple, but with trailing commas (($($repeated: ty,)*), $value: expr) => { field!( ($($repeated),*), $value ) }; // We are provided any type, with no stable name ($name_type: ty, $value: expr) => { field!( $name_type, $value, stringify!($name_type) ) }; // We are provided any type, with a stable name ($name_type: ty, $value: expr, $name: expr) => { $crate::labelled::field_with_name::<$name_type,_>($name, $value) } } /// A trait that strips type-level strings from the labels pub trait IntoValueLabelled { type Output; /// Turns the current HList into a value-labelled one. /// /// Effectively extracts the names and values held inside the individual Fields /// and puts them into ValueFields, which do not have type-level names. /// /// # Examples /// /// ``` /// # #[macro_use] extern crate frunk_core; /// # use frunk_core::labelled::*; /// # use frunk_core::hlist::*; /// # fn main() { /// /// let labelled_hlist = hlist![ /// field!((n, a, m, e), "joe"), /// field!((a, g, e), 3) /// ]; /// // Notice the lack of type-level names /// let value_labelled: Hlist![ValueField<&str>, ValueField<isize>] = labelled_hlist.into_value_labelled(); /// /// assert_eq!( /// value_labelled, /// hlist![ /// ValueField { /// name: "name", /// value: "joe", /// }, /// ValueField { /// name: "age", /// value: 3, /// }, /// ]); /// # } /// ``` fn into_value_labelled(self) -> Self::Output; } impl IntoValueLabelled for HNil { type Output = HNil; fn into_value_labelled(self) -> Self::Output { self } } impl<Label, Value, Tail> IntoValueLabelled for HCons<Field<Label, Value>, Tail> where Tail: IntoValueLabelled, { type Output = HCons<ValueField<Value>, <Tail as IntoValueLabelled>::Output>; fn into_value_labelled(self) -> Self::Output { HCons { head: ValueField { name: self.head.name, value: self.head.value }, tail: self.tail.into_value_labelled(), } } } #[cfg(test)] mod tests { use super::*; // Set up some aliases #[allow(non_camel_case_types)] type abc = (a, b, c); #[allow(non_camel_case_types)] type name = (n, a, m, e); #[allow(non_camel_case_types)] type age = (a, g, e); #[test] fn test_label_new_building() { let l1 = field!(abc, 3); assert_eq!(l1.value, 3); assert_eq!(l1.name, "abc"); let l2 = field!((a, b, c), 3); assert_eq!(l2.value, 3); assert_eq!(l2.name, "abc"); // test named let l3 = field!(abc, 3, "nope"); assert_eq!(l3.value, 3); assert_eq!(l3.name, "nope"); let l4 = field!((a, b, c), 3, "nope"); assert_eq!(l4.value, 3); assert_eq!(l4.name, "nope"); } #[test] fn test_field_construction() { let f1 = field!(age, 3); let f2 = field!((a, g, e), 3); assert_eq!(f1, f2) } #[test] fn test_anonymous_record_usage() { let record = hlist![field!(name, "Joe"), field!((a, g, e), 30)]; let (name, _): (Field<name, _>, _) = record.pluck(); assert_eq!(name.value, "Joe") } #[test] fn test_unlabelling() { let labelled_hlist = hlist![field!(name, "joe"), field!((a, g, e), 3)]; let unlabelled = labelled_hlist.into_unlabelled(); assert_eq!(unlabelled, hlist!["joe", 3]) } #[test] fn test_value_labelling() { let labelled_hlist = hlist![field!(name, "joe"), field!((a, g, e), 3)]; let value_labelled: Hlist![ValueField<&str>, ValueField<isize>] = labelled_hlist.into_value_labelled(); let hlist_pat!(f1, f2) = value_labelled; assert_eq!(f1.name, "name"); assert_eq!(f2.name, "age"); } #[test] fn test_name() { let labelled = field!(name, "joe"); assert_eq!(labelled.name, "name") } }