pub struct Symbol(_);
Expand description
An interned string.
This is provided by the symbol_table
crate.
Internally, egg
frequently compares Var
s and elements of
Language
s. To keep comparisons fast, egg
provides Symbol
a simple
wrapper providing interned strings.
You may wish to use Symbol
in your own Language
s 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"));
A interned string in the global symbol table.
This requires the global
feature on the crate.
GlobalSymbol
is a wrapper around Symbol
that knows to refer to a
built-in, global SymbolTable
. Strings into the global table are never freed.
This enables a lot of convience methods and trait implementations over
GlobalSymbol
(see below). In particular,
you can convert it to &'static str
,
convert From
and Into
a &str
,
and de/serialize using serde
if the serde
feature is enabled.
Implementations§
Trait Implementations§
source§impl Clone for GlobalSymbol
impl Clone for GlobalSymbol
source§fn clone(&self) -> GlobalSymbol
fn clone(&self) -> GlobalSymbol
1.0.0 · source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moresource§impl Debug for GlobalSymbol
impl Debug for GlobalSymbol
source§impl<'de> Deserialize<'de> for GlobalSymbol
impl<'de> Deserialize<'de> for GlobalSymbol
source§fn deserialize<__D>(
__deserializer: __D
) -> Result<GlobalSymbol, <__D as Deserializer<'de>>::Error>where
__D: Deserializer<'de>,
fn deserialize<__D>( __deserializer: __D ) -> Result<GlobalSymbol, <__D as Deserializer<'de>>::Error>where __D: Deserializer<'de>,
source§impl Display for GlobalSymbol
impl Display for GlobalSymbol
source§impl From<&String> for GlobalSymbol
impl From<&String> for GlobalSymbol
source§fn from(s: &String) -> GlobalSymbol
fn from(s: &String) -> GlobalSymbol
source§impl From<&str> for GlobalSymbol
impl From<&str> for GlobalSymbol
source§fn from(s: &str) -> GlobalSymbol
fn from(s: &str) -> GlobalSymbol
source§impl From<GlobalSymbol> for &'static str
impl From<GlobalSymbol> for &'static str
source§fn from(sym: GlobalSymbol) -> &'static str
fn from(sym: GlobalSymbol) -> &'static str
source§impl From<String> for GlobalSymbol
impl From<String> for GlobalSymbol
source§fn from(s: String) -> GlobalSymbol
fn from(s: String) -> GlobalSymbol
source§impl FromStr for GlobalSymbol
impl FromStr for GlobalSymbol
§type Err = Infallible
type Err = Infallible
source§fn from_str(s: &str) -> Result<GlobalSymbol, <GlobalSymbol as FromStr>::Err>
fn from_str(s: &str) -> Result<GlobalSymbol, <GlobalSymbol as FromStr>::Err>
s
to return a value of this type. Read moresource§impl Hash for GlobalSymbol
impl Hash for GlobalSymbol
source§impl Ord for GlobalSymbol
impl Ord for GlobalSymbol
source§fn cmp(&self, other: &GlobalSymbol) -> Ordering
fn cmp(&self, other: &GlobalSymbol) -> Ordering
1.21.0 · source§fn max(self, other: Self) -> Selfwhere
Self: Sized,
fn max(self, other: Self) -> Selfwhere Self: Sized,
source§impl PartialEq<GlobalSymbol> for GlobalSymbol
impl PartialEq<GlobalSymbol> for GlobalSymbol
source§fn eq(&self, other: &GlobalSymbol) -> bool
fn eq(&self, other: &GlobalSymbol) -> bool
self
and other
values to be equal, and is used
by ==
.source§impl PartialOrd<GlobalSymbol> for GlobalSymbol
impl PartialOrd<GlobalSymbol> for GlobalSymbol
source§fn partial_cmp(&self, other: &GlobalSymbol) -> Option<Ordering>
fn partial_cmp(&self, other: &GlobalSymbol) -> Option<Ordering>
1.0.0 · source§fn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
self
and other
) and is used by the <=
operator. Read moresource§impl Serialize for GlobalSymbol
impl Serialize for GlobalSymbol
source§fn serialize<__S>(
&self,
__serializer: __S
) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error>where
__S: Serializer,
fn serialize<__S>( &self, __serializer: __S ) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error>where __S: Serializer,
impl Copy for GlobalSymbol
impl Eq for GlobalSymbol
impl StructuralEq for GlobalSymbol
impl StructuralPartialEq for GlobalSymbol
Auto Trait Implementations§
impl RefUnwindSafe for GlobalSymbol
impl Send for GlobalSymbol
impl Sync for GlobalSymbol
impl Unpin for GlobalSymbol
impl UnwindSafe for GlobalSymbol
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<Q, K> Equivalent<K> for Qwhere
Q: Eq + ?Sized,
K: Borrow<Q> + ?Sized,
impl<Q, K> Equivalent<K> for Qwhere Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,
source§fn equivalent(&self, key: &K) -> bool
fn equivalent(&self, key: &K) -> bool
key
and return true
if they are equal.