pub enum CaseFold {
    Full,
    Ascii,
    Turkic,
    Lithuanian,
}
Expand description

Unicode case folding strategies.

Unicode case folding data supports both implementations that require simple case foldings (where string lengths don’t change), and implementations that allow full case folding (where string lengths may grow). Note that where they can be supported, the full case foldings are superior: for example, they allow “MASSE” and “Maße” to match.

The CaseFold enum supports the folding strategies available in Ruby.

Examples

For Unicode text, the default folding scheme is Full. To make a comparison:

let fold = CaseFold::Full;
assert_eq!(fold.casecmp("MASSE", "Maße"), Ordering::Equal);
assert_eq!(fold.casecmp("São Paulo", "Sao Paulo"), Ordering::Greater);

assert!(fold.case_eq("MASSE", "Maße"));
assert!(!fold.case_eq("São Paulo", "Sao Paulo"));

For text known to be ASCII, Focaccia can make a more performant comparison check:

let fold = CaseFold::Ascii;
assert_eq!(fold.casecmp("Crate: focaccia", "Crate: FOCACCIA"), Ordering::Equal);
assert_eq!(fold.casecmp("Fabled", "failed"), Ordering::Less);

assert!(fold.case_eq("Crate: focaccia", "Crate: FOCACCIA"));
assert!(!fold.case_eq("Fabled", "failed"));

Turkic case folding is similar to full case folding with additional mappings for dotted and dotless I:

let fold = CaseFold::Turkic;
assert_eq!(fold.casecmp("İstanbul", "istanbul"), Ordering::Equal);
assert_ne!(fold.casecmp("İstanbul", "Istanbul"), Ordering::Equal);

assert!(fold.case_eq("İstanbul", "istanbul"));
assert!(!fold.case_eq("İstanbul", "Istanbul"));

Variants§

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Full

Full Unicode case mapping, suitable for most languages (see Turkic and Lithuanian strategies for exceptions). Context-dependent case mapping as described in Table 3-14 of the Unicode standard is currently not supported.

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Ascii

Only the ASCII region, i.e. the characters “A” to “Z” and “a” to “z”, are affected.

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Turkic

Full Unicode case mapping, adapted for Turkic languages (Turkish, Azerbaijani, …). This means that upper case I is mapped to lower case dotless i, and so on.

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Lithuanian

Currently, just full Unicode case mapping. In the future, full Unicode case mapping adapted for Lithuanian (keeping the dot on the lower case i even if there is an accent on top).

Implementations§

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impl CaseFold

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pub const fn new() -> CaseFold

Construct a new full Unicode case folding.

See CaseFold::Full.

Examples
const FOLD: CaseFold = CaseFold::new();

assert_eq!(CaseFold::new(), CaseFold::Full);

assert!(CaseFold::new().case_eq("MASSE", "Maße"));
assert!(!CaseFold::new().case_eq("São Paulo", "Sao Paulo"));
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pub fn casecmp(self, left: &str, right: &str) -> Ordering

Make a case-insensitive string comparison based on the dispatching folding strategy.

Return Ordering::Equal if the given strings match when folding case. For example, when using CaseFold::Full, ß is considered equal to ss. The differences between the folding strategies are documented on the variants of the CaseFold enum.

This function is a wrapper around the underlying scheme-specific functions.

Examples – Full case folding
let fold = CaseFold::Full;
assert_eq!(fold.casecmp("MASSE", "Maße"), Ordering::Equal);
assert_eq!(fold.casecmp("São Paulo", "Sao Paulo"), Ordering::Greater);
Examples – ASCII case folding
let fold = CaseFold::Ascii;
assert_eq!(fold.casecmp("Crate: focaccia", "Crate: FOCACCIA"), Ordering::Equal);
assert_eq!(fold.casecmp("Fabled", "failed"), Ordering::Less);
Examples – Turkic case folding
let fold = CaseFold::Turkic;
assert_eq!(fold.casecmp("İstanbul", "istanbul"), Ordering::Equal);
assert_ne!(fold.casecmp("İstanbul", "Istanbul"), Ordering::Equal);
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pub fn case_eq(self, left: &str, right: &str) -> bool

Make a case-insensitive string equality check based on the dispatching folding strategy.

Return true if the given strings match when folding case. For example, when using CaseFold::Full, ß is considered equal to ss. The differences between the folding strategies are documented on the variants of the CaseFold enum.

This function is a wrapper around the underlying scheme-specific functions.

Examples – Full case folding
let fold = CaseFold::Full;
assert!(fold.case_eq("MASSE", "Maße"));
assert!(!fold.case_eq("São Paulo", "Sao Paulo"));
Examples – ASCII case folding
let fold = CaseFold::Ascii;
assert!(fold.case_eq("Crate: focaccia", "Crate: FOCACCIA"));
assert!(!fold.case_eq("Fabled", "failed"));
Examples – Turkic case folding
let fold = CaseFold::Turkic;
assert!(fold.case_eq("İstanbul", "istanbul"));
assert!(!fold.case_eq("İstanbul", "Istanbul"));

Trait Implementations§

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impl Clone for CaseFold

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fn clone(&self) -> CaseFold

Returns a copy of the value. Read more
1.0.0 · source§

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

Performs copy-assignment from source. Read more
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impl Debug for CaseFold

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

Formats the value using the given formatter. Read more
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impl Default for CaseFold

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fn default() -> CaseFold

Default to full Unicode case folding.

See CaseFold::Full.

Examples
assert_eq!(CaseFold::default(), CaseFold::Full);

assert!(CaseFold::default().case_eq("MASSE", "Maße"));
assert!(!CaseFold::default().case_eq("São Paulo", "Sao Paulo"));
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impl Hash for CaseFold

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fn hash<__H>(&self, state: &mut __H)where
    __H: Hasher,

Feeds this value into the given Hasher. Read more
1.3.0 · source§

fn hash_slice<H>(data: &[Self], state: &mut H)where
    H: Hasher,
    Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl Ord for CaseFold

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fn cmp(&self, other: &CaseFold) -> Ordering

This method returns an Ordering between self and other. Read more
1.21.0 · source§

fn max(self, other: Self) -> Selfwhere
    Self: Sized,

Compares and returns the maximum of two values. Read more
1.21.0 · source§

fn min(self, other: Self) -> Selfwhere
    Self: Sized,

Compares and returns the minimum of two values. Read more
1.50.0 · source§

fn clamp(self, min: Self, max: Self) -> Selfwhere
    Self: Sized + PartialOrd<Self>,

Restrict a value to a certain interval. Read more
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impl PartialEq<CaseFold> for CaseFold

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fn eq(&self, other: &CaseFold) -> bool

This method tests for self and other values to be equal, and is used by ==.
1.0.0 · source§

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl PartialOrd<CaseFold> for CaseFold

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fn partial_cmp(&self, other: &CaseFold) -> Option<Ordering>

This method returns an ordering between self and other values if one exists. Read more
1.0.0 · source§

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more
1.0.0 · source§

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
1.0.0 · source§

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more
1.0.0 · source§

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more
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impl TryFrom<Option<&[u8]>> for CaseFold

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type Error = NoSuchCaseFoldingScheme

The type returned in the event of a conversion error.
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fn try_from(
    value: Option<&[u8]>
) -> Result<CaseFold, <CaseFold as TryFrom<Option<&[u8]>>>::Error>

Performs the conversion.
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impl TryFrom<Option<&str>> for CaseFold

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type Error = NoSuchCaseFoldingScheme

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

Performs the conversion.
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impl Copy for CaseFold

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impl Eq for CaseFold

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impl StructuralEq for CaseFold

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impl StructuralPartialEq for CaseFold

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for Twhere
    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 Twhere
    T: ?Sized,

const: unstable · source§

fn borrow(&self) -> &T

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

const: unstable · source§

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

const: unstable · source§

fn from(t: T) -> T

Returns the argument unchanged.

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

const: unstable · source§

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> ToOwned for Twhere
    T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for Twhere
    U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
const: unstable · source§

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 Twhere
    U: TryFrom<T>,

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

The type returned in the event of a conversion error.
const: unstable · source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.