Struct syntax_pos::symbol::Symbol

pub struct Symbol(_);

A symbol is an interned or gensymed string. A gensym is a symbol that is never equal to any other symbol. E.g.:

assert_eq!(Symbol::intern("x"), Symbol::intern("x"))
assert_ne!(Symbol::gensym("x"), Symbol::intern("x"))
assert_ne!(Symbol::gensym("x"), Symbol::gensym("x"))

Conceptually, a gensym can be thought of as a normal symbol with an invisible unique suffix. Gensyms are useful when creating new identifiers that must not match any existing identifiers, e.g. during macro expansion and syntax desugaring.

Internally, a Symbol is implemented as an index, and all operations (including hashing, equality, and ordering) operate on that index. The use of newtype_index! means that Option<Symbol> only takes up 4 bytes, because newtype_index! reserves the last 256 values for tagging purposes.

Note that Symbol cannot directly be a newtype_index! because it implements fmt::Debug, Encodable, and Decodable in special ways.

Methods

impl Symbol

pub fn intern(string: &str) -> Self

Maps a string to its interned representation.

pub fn gensym(string: &str) -> Self

Gensyms a new usize, using the current interner.

pub fn gensymed(self) -> Self

pub fn is_gensymed(self) -> bool

pub fn as_str(self) -> LocalInternedString

pub fn as_interned_str(self) -> InternedString

pub fn as_u32(self) -> u32

Trait Implementations

impl Clone for Symbol

fn clone(&self) -> Symbol

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Ord for Symbol

fn cmp(&self, other: &Symbol) -> 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.

fn clamp(self, min: Self, max: Self) -> Self

🔬 This is a nightly-only experimental API. (clamp)

Restrict a value to a certain interval.

impl Eq for Symbol

impl Copy for Symbol

impl PartialOrd<Symbol> for Symbol

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

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

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

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

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

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

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

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

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

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

impl PartialEq<Symbol> for Symbol

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

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

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

This method tests for !=.

impl Debug for Symbol

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

Formats the value using the given formatter.

impl Display for Symbol

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

Formats the value using the given formatter.

impl Hash for Symbol

fn hash<__H: Hasher>(&self, state: &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 Encodable for Symbol

fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error>

impl Decodable for Symbol

fn decode<D: Decoder>(d: &mut D) -> Result<Symbol, D::Error>