Enum logos::Filter

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pub enum Filter<T> {
    Emit(T),
    Skip,
}
Expand description

Type that can be returned from a callback, either producing a field for a token, or skipping it.

§Example

use logos::{Logos, Filter};

#[derive(Logos, Debug, PartialEq)]
enum Token {
    #[regex(r"[ \n\f\t]+", logos::skip)]
    Ignored,

    #[regex("[0-9]+", |lex| {
        let n: u64 = lex.slice().parse().unwrap();

        // Only emit a token if `n` is an even number
        match n % 2 {
            0 => Filter::Emit(n),
            _ => Filter::Skip,
        }
    })]
    EvenNumber(u64)
}

let tokens: Vec<_> = Token::lexer("20 11 42 23 100 8002").collect();

assert_eq!(
    tokens,
    &[
        Ok(Token::EvenNumber(20)),
        // skipping 11
        Ok(Token::EvenNumber(42)),
        // skipping 23
        Ok(Token::EvenNumber(100)),
        Ok(Token::EvenNumber(8002))
    ]
);

Variants§

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Emit(T)

Emit a token with a given value T. Use () for unit variants without fields.

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Skip

Skip current match, analog to Skip.

Auto Trait Implementations§

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impl<T> Freeze for Filter<T>
where T: Freeze,

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impl<T> RefUnwindSafe for Filter<T>
where T: RefUnwindSafe,

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impl<T> Send for Filter<T>
where T: Send,

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impl<T> Sync for Filter<T>
where T: Sync,

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impl<T> Unpin for Filter<T>
where T: Unpin,

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impl<T> UnwindSafe for Filter<T>
where T: UnwindSafe,

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.