Struct egg::Symbol

pub struct Symbol(_);

An interned string.

Internally, egg frequently compares Vars and elements of Languages. To keep comparisons fast, egg provides Symbol a simple wrapper providing interned strings.

You may wish to use Symbol in your own Languages to increase performance and keep enode sizes down (a Symbol is only 4 bytes, compared to 24 for a String.)

A Symbol is simply a wrapper around an integer. When creating a Symbol from a string, egg looks up it up in a global table, returning the index (inserting it if not found). That integer is used to cheaply implement Copy, Clone, PartialEq, Eq, PartialOrd, Ord, and Hash.

The internal symbol cache leaks the strings, which should be fine if you only put in things like variable names and identifiers.

Example

use egg::Symbol;

assert_eq!(Symbol::from("foo"), Symbol::from("foo"));
assert_eq!(Symbol::from("foo"), "foo".parse().unwrap());

assert_ne!(Symbol::from("foo"), Symbol::from("bar"));

Implementations

impl Symbol

pub fn as_str(self) -> &'static str

Get the string that this symbol represents

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 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<S: AsRef<str>> From<S> for Symbol

fn from(s: S) -> Self

Performs the conversion.

impl From<Symbol> for &'static str

fn from(s: Symbol) -> Self

Performs the conversion.

impl FromStr for Symbol

type Err = Infallible

The associated error which can be returned from parsing.

fn from_str(s: &str) -> Result<Self, Self::Err>

Parses a string s to return a value of this type.

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 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

Restrict a value to a certain interval.

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 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: &Rhs) -> bool

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

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

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

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

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

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

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

impl Copy for Symbol

impl Eq for Symbol

impl StructuralEq for Symbol

impl StructuralPartialEq for Symbol