Enum Either 

pub enum Either<A, B, C = Invalid, D = Invalid> {
    First(A),
    Second(B),
    Third(C),
    Fourth(D),
}

Disjunctive A or B or optional C or D tried in that order. When C and D are not used, they are set to Invalid.

Variants

First(A)

The first alternative

Second(B)

The second alternative

Third(C)

The third alternative

Fourth(D)

The fourth alternative

Implementations

impl<A, B, C, D> Either<A, B, C, D>

where C: 'static, D: 'static,

pub fn fold2<R, FA, FB>(self, first_fn: FA, second_fn: FB) -> R

where FA: FnOnce(A) -> R, FB: FnOnce(B) -> R,

Deconstructs an Either with 2 alternatives and produces a common result type, by applying one of the two functions depending on the alternative.

Panics

When the variant is Either::Third or Either::Fourth

Example

let either = Either::<LiteralInteger, Ident>::First(LiteralInteger::new(42));
let result: String = either.fold2(
    |a| a.tokens_to_string(),
    |b| b.tokens_to_string(),
);
assert_eq!(result, "42");

pub fn fold3<R, FA, FB, FC>( self, first_fn: FA, second_fn: FB, third_fn: FC, ) -> R

where FA: FnOnce(A) -> R, FB: FnOnce(B) -> R, FC: FnOnce(C) -> R,

Deconstructs an Either with 3 alternatives and produces a common result type, by applying one of the three functions depending on the alternative.

Panics

When the variant is Either::Fourth

pub fn fold4<R, FA, FB, FC, FD>( self, first_fn: FA, second_fn: FB, third_fn: FC, fourth_fn: FD, ) -> R

where FA: FnOnce(A) -> R, FB: FnOnce(B) -> R, FC: FnOnce(C) -> R, FD: FnOnce(D) -> R,

Deconstructs an Either with 4 alternatives and produces a common result type, by applying one of the provided functions.

pub fn into2<T>(self) -> T

where A: Into<T>, B: Into<T>,

Deconstructs an Either with 2 alternatives and produces a common result type for types that implement Into<T>.

Panics

When more then two alternatives are used.

Example

let either = Either::<LiteralInteger, Ident>::First(LiteralInteger::new(42));
let tt: TokenTree = either.into2();
assert_eq!(tt.tokens_to_string(), "42");

pub fn into3<T>(self) -> T

where A: Into<T>, B: Into<T>, C: Into<T>,

Deconstructs an Either with 3 alternatives and produces a common result type for types that implement Into<T>.

Panics

When more then three alternatives are used.

pub fn into4<T>(self) -> T

where A: Into<T>, B: Into<T>, C: Into<T>, D: Into<T>,

Deconstructs an Either with 4 alternatives and produces a common result type for types that implement Into<T>.

Trait Implementations

impl<A, B, C, D> Clone for Either<A, B, C, D>

where A: Clone, B: Clone, C: Clone, D: Clone,

fn clone(&self) -> Either<A, B, C, D>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<A, B, C, D> Debug for Either<A, B, C, D>

where A: Debug, B: Debug, C: Debug + 'static, D: Debug + 'static,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<A, B, C, D> Parser for Either<A, B, C, D>

where A: Parse, B: Parse, C: Parse, D: Parse,

fn parser( tokens: &mut ShadowCountedIter<'_, <TokenStream as IntoIterator>::IntoIter>, ) -> Result<Either<A, B, C, D>, Error>

The actual parsing function that must be implemented. This mutates the tokens iterator directly. It should not be called from user code except for implementing parsers itself and then only when the rules below are followed.

impl<A, B, C, D> ToTokens for Either<A, B, C, D>

where A: ToTokens, B: ToTokens, C: ToTokens, D: ToTokens,

fn to_tokens(&self, tokens: &mut TokenStream)

Write &self to the given TokenStream.

fn to_token_iter( &self, ) -> ShadowCountedIter<'_, <TokenStream as IntoIterator>::IntoIter>

Convert &self into a TokenIter object.

fn into_token_iter<'a>( self, ) -> ShadowCountedIter<'a, <TokenStream as IntoIterator>::IntoIter>

where Self: Sized,

Convert self into a TokenIter object.

fn to_token_stream(&self) -> TokenStream

Convert &self into a TokenStream object.

fn into_token_stream(self) -> TokenStream

where Self: Sized,

Convert self into a TokenStream object.

fn tokens_to_string(&self) -> String

Convert &self into a String object. This is mostly used in the test suite to compare the outputs. When the input is a &str then this parses it and returns a normalized String.