Struct edn::symbols::Keyword

pub struct Keyword(_);

A keyword is a symbol, optionally with a namespace, that prints with a leading colon. This concept is imported from Clojure, as it features in EDN and the query syntax that we use.

Clojure's constraints are looser than ours, allowing empty namespaces or names:

user=> (keyword "" "")
:/
user=> (keyword "foo" "")
:foo/
user=> (keyword "" "bar")
:/bar

We think that's nonsense, so we only allow keywords like :bar and :foo/bar, with both namespace and main parts containing no whitespace and no colon or slash:

let bar     = Keyword::plain("bar");                         // :bar
let foo_bar = Keyword::namespaced("foo", "bar");        // :foo/bar
assert_eq!("bar", bar.name());
assert_eq!(None, bar.namespace());
assert_eq!("bar", foo_bar.name());
assert_eq!(Some("foo"), foo_bar.namespace());

If you're not sure whether your input is well-formed, you should use a parser or a reader function first to validate. TODO: implement read.

Callers are expected to follow these rules: http://www.clojure.org/reference/reader#_symbols

Future: fast equality (interning?) for keywords.

Methods

impl Keyword

pub fn plain<T>(name: T) -> Self where
    T: Into<String>, 

impl Keyword

pub fn namespaced<N, T>(namespace: N, name: T) -> Self where
    N: AsRef<str>,
    T: AsRef<str>, 

Creates a new Keyword.

Examples

let keyword = Keyword::namespaced("foo", "bar");
assert_eq!(keyword.to_string(), ":foo/bar");

See also the kw! macro in the main mentat crate.

pub fn name(&self) -> &str

pub fn namespace(&self) -> Option<&str>

pub fn components<'a>(&'a self) -> (&'a str, &'a str)

pub fn is_backward(&self) -> bool

Whether this Keyword should be interpreted in reverse order. For example, the two following snippets are identical:

[?y :person/friend ?x]
[?x :person/hired ?y]

[?y :person/friend ?x]
[?y :person/_hired ?x]

Examples

assert!(!Keyword::namespaced("foo", "bar").is_backward());
assert!(Keyword::namespaced("foo", "_bar").is_backward());

pub fn is_forward(&self) -> bool

Whether this Keyword should be interpreted in forward order. See symbols::Keyword::is_backward.

Examples

assert!(Keyword::namespaced("foo", "bar").is_forward());
assert!(!Keyword::namespaced("foo", "_bar").is_forward());

pub fn is_namespaced(&self) -> bool

pub fn to_reversed(&self) -> Keyword

Returns a Keyword with the same namespace and a 'backward' name. See symbols::Keyword::is_backward.

Returns a forward name if passed a reversed keyword; i.e., this function is its own inverse.

Examples

let nsk = Keyword::namespaced("foo", "bar");
assert!(!nsk.is_backward());
assert_eq!(":foo/bar", nsk.to_string());

let reversed = nsk.to_reversed();
assert!(reversed.is_backward());
assert_eq!(":foo/_bar", reversed.to_string());

pub fn unreversed(&self) -> Option<Keyword>

If this Keyword is 'backward' (see symbols::Keyword::is_backward), return Some('forward name'); otherwise, return None.

Examples

let nsk = Keyword::namespaced("foo", "bar");
assert_eq!(None, nsk.unreversed());

let reversed = nsk.to_reversed();
assert_eq!(Some(nsk), reversed.unreversed());

Trait Implementations

impl From<Keyword> for EntidOrIdent

fn from(v: Keyword) -> Self

Performs the conversion.

impl From<Keyword> for PatternNonValuePlace

fn from(value: Keyword) -> Self

Performs the conversion.

impl From<Keyword> for PatternValuePlace

fn from(value: Keyword) -> Self

Performs the conversion.

impl Clone for Keyword

fn clone(&self) -> Keyword

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Keyword

fn fmt(&self, __arg_0: &mut Formatter) -> Result

Formats the value using the given formatter.

impl Eq for Keyword

impl Hash for Keyword

fn hash<__H: Hasher>(&self, __arg_0: &mut __H)

Feeds this value into the given [Hasher].

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

Feeds a slice of this type into the given [Hasher].

impl Ord for Keyword

fn cmp(&self, __arg_0: &Keyword) -> Ordering

This method returns an Ordering between self and other.

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

Compares and returns the maximum of two values.

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

Compares and returns the minimum of two values.

impl PartialOrd for Keyword

fn partial_cmp(&self, __arg_0: &Keyword) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, __arg_0: &Keyword) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, __arg_0: &Keyword) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, __arg_0: &Keyword) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, __arg_0: &Keyword) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl PartialEq for Keyword

fn eq(&self, __arg_0: &Keyword) -> bool

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

fn ne(&self, __arg_0: &Keyword) -> bool

This method tests for !=.

impl Display for Keyword

fn fmt(&self, f: &mut Formatter) -> Result

Print the keyword in EDN format.

Examples

assert_eq!(":baz", Keyword::plain("baz").to_string());
assert_eq!(":bar/baz", Keyword::namespaced("bar", "baz").to_string());
assert_eq!(":bar/_baz", Keyword::namespaced("bar", "baz").to_reversed().to_string());
assert_eq!(":bar/baz", Keyword::namespaced("bar", "baz").to_reversed().to_reversed().to_string());