Struct knightrs::Variable

pub struct Variable(_);

A variable within Knight.

Note that there is no way to create Variables directly—they must to be fetched via Environment::get.

All variables with the same from the same Environment are identical. Updating any one of them (via Variable::assign) will update them all.

Implementations

impl Variable

#[must_use]

pub fn name(&self) -> &str

Fetches the name of the variable.

Examples

let mut env = Environment::default();
let var = env.get("plato");

assert_eq!(var.name(), "plato");

#[must_use = "this simply checks to see if it's assigned, and doesn't do anthing on its own."]

pub fn is_assigned(&self) -> bool

Checks to see if the variable has been assigned to yet.

Examples

let mut env = Environment::default();
let var = env.get("plato");

assert!(!var.is_assigned());
 
var.assign(Value::Null);
assert!(var.is_assigned());

pub fn assign(&self, value: Value)

Associates value with this variable, so that fetch will return it.

Any previously associated Values are discarded.

Note that all variables with the same name from the same environment will be affected. After all, that’s the point of having variables.

Examples

let mut env = Environment::default();
let var = env.get("plato");
let var2 = env.get("plato");
 
var.assign(Value::Null);
assert_eq!(var.fetch().unwrap(), Value::Null);
assert_eq!(var2.fetch().unwrap(), Value::Null);

#[must_use = "simply fetching a value does nothing; the return value should be inspected."]

pub fn fetch(&self) -> Option<Value>

Returns the last value associated with this variable, or None if nothing’s been associated.

Note that all variables with the same name from the same environment will be affected. After all, that’s the point of having variables.

Examples

let mut env = Environment::default();
let var = env.get("plato");
 
assert_eq!(var.fetch(), None);
var.assign(Value::from(true));
assert_eq!(var.fetch(), Some(Value::from(true)));

pub fn run(&self) -> Result<Value>

Executes this variable, returning an Error if the variable doesn’t exist.

Trait Implementations

impl Borrow<str> for Variable

fn borrow(&self) -> &str

Immutably borrows from an owned value.

impl Clone for Variable

fn clone(&self) -> Variable

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Variable

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

Formats the value using the given formatter.

impl From<Variable> for Value

fn from(variable: Variable) -> Self

Performs the conversion.

impl Hash for Variable

fn hash<H: Hasher>(&self, h: &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 PartialEq<Variable> for Variable

fn eq(&self, rhs: &Self) -> bool

Checks to see if two variables are the same.

This will only return true if they both originate from the same Environment and have the same name.

#[must_use]

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

This method tests for !=.

impl Eq for Variable