Struct mentat_transaction::query::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) -> Keyword where
    T: Into<String>, 

impl Keyword

pub fn namespaced<N, T>(namespace: N, name: T) -> Keyword 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 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 Hash for Keyword

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

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 PartialOrd<Keyword> 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 From<Keyword> for PatternNonValuePlace

fn from(value: Keyword) -> PatternNonValuePlace

Performs the conversion.

impl From<Keyword> for EntidOrIdent

fn from(v: Keyword) -> EntidOrIdent

Performs the conversion.

impl From<Keyword> for PatternValuePlace

fn from(value: Keyword) -> PatternValuePlace

Performs the conversion.

impl Debug for Keyword

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

Formats the value using the given formatter.

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 Serialize for Keyword

fn serialize<__S>(
    &self,
    __serializer: __S
) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error> where
    __S: Serializer, 

Serialize this value into the given Serde serializer.

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 Eq for Keyword

impl Display for Keyword

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

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());

impl PartialEq<Keyword> 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<'de> Deserialize<'de> for Keyword

fn deserialize<__D>(
    __deserializer: __D
) -> Result<Keyword, <__D as Deserializer<'de>>::Error> where
    __D: Deserializer<'de>, 

Deserialize this value from the given Serde deserializer.

impl From<Keyword> for TypedValue

fn from(value: Keyword) -> TypedValue

Performs the conversion.