Enum lexpr::value::Value

pub enum Value {
    Nil,
    Null,
    Bool(bool),
    Number(Number),
    Char(char),
    String(Box<str>),
    Symbol(Box<str>),
    Keyword(Box<str>),
    Bytes(Box<[u8]>),
    Cons(Cons),
    Vector(Box<[Value]>),
}

Represents an S-expression value.

See the lexpr::value module documentation for usage examples.

Variants

Nil

The special "nil" value.

This is kind of an oddball value. In traditional Lisps (e.g., Common Lisp or Emacs Lisp) the empty list can be written as the symbol nil, while in Scheme, nil is just a regular symbol. Furthermore, traditional Lisps don't have a separate boolean data type, and represent true and false by the symbols t and nil instead. The lexpr parser can be instructed to parse the nil symbol as the Nil value (see NilSymbol::Special), allowing to choose its representation when converting to text again (see NilSyntax). Note that the empty list, when written as () or implicitly constructed as a list terminator, is always parsed as Value::Null, not Value::Nil.

In addition to being useful for conversions between S-expression variants, this value is also potentially returned when using the square bracket indexing operator on Value.

Null

The empty list.

This value terminates a chain of cons cells forming a proper list.

Bool(bool)

A boolean value.

Number(Number)

A number.

Char(char)

A character.

String(Box<str>)

A string.

Symbol(Box<str>)

A symbol.

Keyword(Box<str>)

A keyword.

Bytes(Box<[u8]>)

A byte vector.

Cons(Cons)

Represents a Lisp "cons cell".

Cons cells are often used to form singly-linked lists.

let v = sexp!((a list 1 2 3));
assert!(v.is_cons());
assert_eq!(v[4], sexp!(3));

Vector(Box<[Value]>)

A Lisp vector.

Methods

impl Value

pub fn symbol(name: impl Into<Box<str>>) -> Self

Construct a symbol, given its name.

pub fn keyword(name: impl Into<Box<str>>) -> Self

Construct a keyword, given its name.

let value = Value::keyword("foo");
assert!(value.is_keyword());
assert_eq!(value.as_keyword().unwrap(), "foo");

pub fn string(s: impl Into<Box<str>>) -> Self

Construct a string.

let value = Value::string("foo");
assert!(value.is_string());
assert_eq!(value.as_str().unwrap(), "foo");

pub fn bytes(bv: impl Into<Box<[u8]>>) -> Self

Construct a byte vector.

let value = Value::bytes(b"foo" as &[u8]);
assert!(value.is_bytes());
assert_eq!(value.as_bytes().unwrap(), b"foo");

pub fn cons<T, U>(car: T, cdr: U) -> Self where
    T: Into<Value>,
    U: Into<Value>, 

Create a cons cell given its car and cdr fields.

let value = Value::cons(1, Value::Null);
assert!(value.is_cons());
assert_eq!(value.as_pair().unwrap(), (&Value::from(1), &Value::Null));

Note that you can also construct a cons cell from a Rust pair via the From trait:

let value = Value::from((42, "answer"));
assert!(value.is_cons());
assert_eq!(value.as_pair().unwrap(), (&Value::from(42), &Value::string("answer")));

pub fn list<I>(elements: I) -> Self where
    I: IntoIterator,
    I::Item: Into<Value>, 

Create a list value from elements convertible into Value.

assert_eq!(Value::list(vec![1, 2, 3]), sexp!((1 2 3)));

pub fn is_list(&self) -> bool

Returns true if the value is a (proper) list.

pub fn is_dotted_list(&self) -> bool

Returns true if the value is a dotted (improper) list.

Note that all values that are not pairs are considered dotted lists.

let list = sexp!((1 2 3));
assert!(!list.is_dotted_list());
let dotted = sexp!((1 2 . 3));
assert!(dotted.is_dotted_list());

pub fn append<I, T>(elements: I, tail: T) -> Self where
    I: IntoIterator,
    I::Item: Into<Value>,
    T: Into<Value>, 

Create a list value from elements convertible into Value, using a given value as a tail.

assert_eq!(Value::append(vec![1u32, 2], 3), sexp!((1 2 . 3)));
assert_eq!(Value::append(vec![1u32, 2, 3], sexp!((4 5))), sexp!((1 2 3 4 5)));

pub fn vector<I>(elements: I) -> Self where
    I: IntoIterator,
    I::Item: Into<Value>, 

Create a vector value from elements convertible into Value.

assert_eq!(Value::vector(vec![1u32, 2, 3]), sexp!(#(1 2 3)));

pub fn is_string(&self) -> bool

Returns true if the value is a String. Returns false otherwise.

For any Value on which is_string returns true, as_str is guaranteed to return the string slice.

let v = sexp!(((a . "some string") (b . #f)));

assert!(v["a"].is_string());

// The boolean `false` is not a string.
assert!(!v["b"].is_string());

pub fn as_str(&self) -> Option<&str>

If the value is a String, returns the associated str. Returns None otherwise.

let v = sexp!(((a . "some string") (b . #f)));

assert_eq!(v["a"].as_str(), Some("some string"));

// The boolean `false` is not a string.
assert_eq!(v["b"].as_str(), None);

// S-expression values are printed in S-expression
// representation, so strings are in quotes.
//    The value is: "some string"
println!("The value is: {}", v["a"]);

// Rust strings are printed without quotes.
//
//    The value is: some string
println!("The value is: {}", v["a"].as_str().unwrap());

pub fn is_symbol(&self) -> bool

Returns true if the value is a symbol. Returns false otherwise.

For any Value on which is_symbol returns true, as_symbol is guaranteed to return the string slice.

let v = sexp!((#:foo bar "baz"));

assert!(v[1].is_symbol());

// Keywords and strings are not symbols.
assert!(!v[0].is_symbol());
assert!(!v[2].is_symbol());

pub fn as_symbol(&self) -> Option<&str>

If the value is a symbol, returns the associated str. Returns None otherwise.

let v = sexp!(foo);

assert_eq!(v.as_symbol(), Some("foo"));

pub fn is_keyword(&self) -> bool

Returns true if the value is a keyword. Returns false otherwise.

For any Value on which is_keyword returns true, as_keyword is guaranteed to return the string slice.

let v = sexp!((#:foo bar "baz"));

assert!(v[0].is_keyword());

// Symbols and strings are not keywords.
assert!(!v[1].is_keyword());
assert!(!v[2].is_keyword());

pub fn as_keyword(&self) -> Option<&str>

If the value is a keyword, returns the associated str. Returns None otherwise.

let v = sexp!(#:foo);

assert_eq!(v.as_keyword(), Some("foo"));

pub fn as_name(&self) -> Option<&str>

Get the name of a symbol or keyword, or the value of a string.

This is useful if symbols, keywords and strings need to be treated equivalently in some context.

let kw = sexp!(#:foo);
assert_eq!(kw.as_name(), Some("foo"));

let sym = sexp!(bar);
assert_eq!(sym.as_name(), Some("bar"));

let s = sexp!("baz");
assert_eq!(s.as_name(), Some("baz"));

pub fn is_bytes(&self) -> bool

Returns true if the value is a byte vector. Returns false otherwise.

For any Value on which is_bytes returns true, as_bytes is guaranteed to return the byte slice.

let v = sexp!(((a . ,(b"some bytes" as &[u8])) (b . "string")));

assert!(v["a"].is_bytes());

// A string is not a byte vector.
assert!(!v["b"].is_bytes());

pub fn as_bytes(&self) -> Option<&[u8]>

If the value is a byte vector, returns the associated byte slice. Returns None otherwise.

let v = sexp!(((a . ,(b"some bytes" as &[u8])) (b . "string")));

assert_eq!(v["a"].as_bytes(), Some(b"some bytes" as &[u8]));

// A string is not a byte vector.
assert_eq!(v["b"].as_bytes(), None);

pub fn is_number(&self) -> bool

Return true if the value is a number.

pub fn as_number(&self) -> Option<&Number>

For numbers, return a reference to them. For other values, return None.

pub fn is_i64(&self) -> bool

Returns true if the value is an integer between i64::MIN and i64::MAX.

For any Value on which is_i64 returns true, as_i64 is guaranteed to return the integer value.

let big = i64::max_value() as u64 + 10;
let v = sexp!(((a . 64) (b . ,big) (c . 256.0)));

assert!(v["a"].is_i64());

// Greater than i64::MAX.
assert!(!v["b"].is_i64());

// Numbers with a decimal point are not considered integers.
assert!(!v["c"].is_i64());

pub fn is_u64(&self) -> bool

Returns true if the value is an integer between zero and u64::MAX.

For any Value on which is_u64 returns true, as_u64 is guaranteed to return the integer value.

let v = sexp!(((a . 64) (b . -64) (c . 256.0)));

assert!(v["a"].is_u64());

// Negative integer.
assert!(!v["b"].is_u64());

// Numbers with a decimal point are not considered integers.
assert!(!v["c"].is_u64());

pub fn is_f64(&self) -> bool

Returns true if the value is a number that can be represented by f64.

For any Value on which is_f64 returns true, as_f64 is guaranteed to return the floating point value.

Currently this function returns true if and only if both is_i64 and is_u64 return false but this is not a guarantee in the future.

let v = sexp!(((a . 256.0) (b . 64) (c . -64)));

assert!(v["a"].is_f64());

// Integers.
assert!(!v["b"].is_f64());
assert!(!v["c"].is_f64());

pub fn as_i64(&self) -> Option<i64>

If the value is an integer, represent it as i64 if possible. Returns None otherwise.

let big = i64::max_value() as u64 + 10;
let v = sexp!(((a . 64) (b . ,big) (c . 256.0)));

assert_eq!(v["a"].as_i64(), Some(64));
assert_eq!(v["b"].as_i64(), None);
assert_eq!(v["c"].as_i64(), None);

pub fn as_u64(&self) -> Option<u64>

If the value is an integer, represent it as u64 if possible. Returns None otherwise.

let v = sexp!(((a . 64) (b . -64) (c . 256.0)));

assert_eq!(v["a"].as_u64(), Some(64));
assert_eq!(v["b"].as_u64(), None);
assert_eq!(v["c"].as_u64(), None);

pub fn as_f64(&self) -> Option<f64>

If the value is a number, represent it as f64 if possible. Returns None otherwise.

let v = sexp!(((a . 256.0) (b . 64) (c . -64)));

assert_eq!(v["a"].as_f64(), Some(256.0));
assert_eq!(v["b"].as_f64(), Some(64.0));
assert_eq!(v["c"].as_f64(), Some(-64.0));

pub fn is_boolean(&self) -> bool

Returns true if the value is a Boolean. Returns false otherwise.

For any Value on which is_boolean returns true, as_bool is guaranteed to return the boolean value.

let v = sexp!(((a . #f) (b . #nil)));

assert!(v["a"].is_boolean());

// The nil value is special, and not a boolean.
assert!(!v["b"].is_boolean());

pub fn as_bool(&self) -> Option<bool>

If the value is a Boolean, returns the associated bool. Returns None otherwise.

let v = sexp!(((a . #f) (b . "false")));

assert_eq!(v["a"].as_bool(), Some(false));

// The string `"false"` is a string, not a boolean.
assert_eq!(v["b"].as_bool(), None);

pub fn is_char(&self) -> bool

Returns true if the value is a character. Returns false otherwise.

pub fn as_char(&self) -> Option<char>

If the value is a character, returns the associated char. Returns None otherwise.

let v = sexp!(((a . 'c') (b . "c")));

assert_eq!(v["a"].as_char(), Some('c'));

// The string `"c"` is a single-character string, not a character.
assert_eq!(v["b"].as_char(), None);

pub fn is_nil(&self) -> bool

Returns true if the value is Nil. Returns false otherwise.

For any Value on which is_nil returns true, as_nil is guaranteed to return Some(()).

let v = sexp!(((a . #nil) (b . #f)));

assert!(v["a"].is_nil());

// The boolean `false` is not nil.
assert!(!v["b"].is_nil());

pub fn as_nil(&self) -> Option<()>

If the value is Nil, returns (). Returns None otherwise.

let v = sexp!(((a . #nil) (b . #f) (c . ())));

assert_eq!(v["a"].as_nil(), Some(()));

// The boolean `false` is not nil.
assert_eq!(v["b"].as_nil(), None);
// Neither is the empty list.
assert_eq!(v["c"].as_nil(), None);

pub fn is_null(&self) -> bool

Returns true if the value is Null. Returns false otherwise.

pub fn as_null(&self) -> Option<()>

If the value is Null, returns (). Returns None otherwise.

pub fn is_cons(&self) -> bool

Returns true if the value is a cons cell. Returns False otherwise.

pub fn as_cons(&self) -> Option<&Cons>

If the value is a cons cell, returns a reference to it. Returns None otherwise.

pub fn as_cons_mut(&mut self) -> Option<&mut Cons>

If the value is a cons cell, returns a mutable reference to it. Returns None otherwise.

pub fn as_pair(&self) -> Option<(&Value, &Value)>

If the value is a cons cell, return references to its car and cdr fields.

let cell = sexp!((foo . bar));
assert_eq!(cell.as_pair(), Some((&sexp!(foo), &sexp!(bar))));
assert_eq!(sexp!("not-a-pair").as_pair(), None);

pub fn is_vector(&self) -> bool

Returns true if the value is a vector.

pub fn as_slice(&self) -> Option<&[Value]>

If the value is a vector, return a reference to its elements.

let v = sexp!(#(1 2 "three"));
let slice: &[Value] = &[sexp!(1), sexp!(2), sexp!("three")];
assert_eq!(v.as_slice(), Some(slice));

pub fn as_slice_mut(&mut self) -> Option<&mut [Value]>

If the value is a vector, return a mutable reference to its elements.

let mut v = sexp!(#(1 2 "three"));
v.as_slice_mut().unwrap()[2] = sexp!(3);
let slice: &[Value] = &[sexp!(1), sexp!(2), sexp!(3)];
assert_eq!(v.as_slice(), Some(slice));

pub fn to_vec(&self) -> Option<Vec<Value>>

Attempts conversion to a vector, cloning the values.

For proper lists (including Value::Null), this returns a vector of values. If you want to handle improper list in a similar way, combine as_cons and the Cons::to_vec method.

assert_eq!(sexp!((1 2 3)).to_vec(), Some(vec![sexp!(1), sexp!(2), sexp!(3)]));
assert_eq!(sexp!(()).to_vec(), Some(vec![]));
assert_eq!(sexp!((1 2 . 3)).to_vec(), None);

pub fn to_ref_vec(&self) -> Option<Vec<&Value>>

Attempts conversion to a vector, taking references to the values.

For proper lists (including Value::Null), this returns a vector of value references. If you want to handle improper list in a similar way, combine as_cons and the Cons::to_ref_vec method.

assert_eq!(sexp!((1 2 3)).to_ref_vec(), Some(vec![&sexp!(1), &sexp!(2), &sexp!(3)]));
assert_eq!(sexp!(()).to_ref_vec(), Some(vec![]));
assert_eq!(sexp!((1 2 . 3)).to_ref_vec(), None);

pub fn get<I: Index>(&self, index: I) -> Option<&Value>

Index into a S-expression list. A string or Value value can be used to access a value in an association list, and a usize index can be used to access the n-th element of a list.

For indexing into association lists, the given string will match strings, symbols and keywords.

Returns None if the type of self does not match the type of the index, for example if the index is a string and self is not an association list. Also returns None if the given key does not exist in the map or the given index is not within the bounds of the list; note that the tail of an improper list is also considered out-of-bounds.

In Scheme terms, this method can be thought of a combination of assoc-ref and list-ref, depending on the argument type. If you want to look up a number in an association list, use an Value value containing that number.

let alist = sexp!((("A" . 65) (B . 66) (#:C . 67) (42 . "The answer")));
assert_eq!(alist.get("A").unwrap(), &sexp!(65));
assert_eq!(alist.get("B").unwrap(), &sexp!(66));
assert_eq!(alist.get("C").unwrap(), &sexp!(67));
assert_eq!(alist.get(sexp!(42)).unwrap(), &sexp!("The answer"));

let list = sexp!(("A" "B" "C"));
assert_eq!(*list.get(2).unwrap(), sexp!("C"));

assert_eq!(list.get("A"), None);

Square brackets can also be used to index into a value in a more concise way. This returns the nil value in cases where get would have returned None. See Index for details.

let alist = sexp!((
    ("A" . ("a" "á" "à"))
    ("B" . ((b . 42) (c . 23)))
    ("C" . ("c" "ć" "ć̣" "ḉ"))
));
assert_eq!(alist["B"][0], sexp!((b . 42)));
assert_eq!(alist["C"][1], sexp!("ć"));

assert_eq!(alist["D"], sexp!(#nil));
assert_eq!(alist[0]["x"]["y"]["z"], sexp!(#nil));

Trait Implementations

impl Index for Value

fn index_into<'v>(&self, v: &'v Value) -> Option<&'v Value>

impl From<u8> for Value

fn from(n: u8) -> Self

Performs the conversion.

impl From<u16> for Value

fn from(n: u16) -> Self

Performs the conversion.

impl From<u32> for Value

fn from(n: u32) -> Self

Performs the conversion.

impl From<u64> for Value

fn from(n: u64) -> Self

Performs the conversion.

impl From<i8> for Value

fn from(n: i8) -> Self

Performs the conversion.

impl From<i16> for Value

fn from(n: i16) -> Self

Performs the conversion.

impl From<i32> for Value

fn from(n: i32) -> Self

Performs the conversion.

impl From<i64> for Value

fn from(n: i64) -> Self

Performs the conversion.

impl From<f32> for Value

fn from(n: f32) -> Self

Performs the conversion.

impl From<f64> for Value

fn from(n: f64) -> Self

Performs the conversion.

impl From<char> for Value

fn from(c: char) -> Self

Performs the conversion.

impl<'_> From<&'_ str> for Value

fn from(s: &str) -> Self

Performs the conversion.

impl<'a> From<Cow<'a, str>> for Value

fn from(s: Cow<'a, str>) -> Self

Performs the conversion.

impl From<Box<str>> for Value

fn from(s: Box<str>) -> Self

Performs the conversion.

impl From<String> for Value

fn from(s: String) -> Self

Performs the conversion.

impl From<bool> for Value

fn from(v: bool) -> Self

Performs the conversion.

impl<'_> From<&'_ [u8]> for Value

fn from(bytes: &[u8]) -> Self

Performs the conversion.

impl From<Box<[u8]>> for Value

fn from(bytes: Box<[u8]>) -> Self

Performs the conversion.

impl From<Vec<u8>> for Value

fn from(bytes: Vec<u8>) -> Self

Performs the conversion.

impl From<Number> for Value

fn from(n: Number) -> Self

Performs the conversion.

impl<T, U> From<(T, U)> for Value where
    T: Into<Value>,
    U: Into<Value>, 

fn from((car, cdr): (T, U)) -> Self

Performs the conversion.

impl From<Cons> for Value

fn from(pair: Cons) -> Self

Performs the conversion.

impl From<Vec<Value>> for Value

fn from(elts: Vec<Value>) -> Self

Performs the conversion.

impl From<Box<[Value]>> for Value

fn from(elts: Box<[Value]>) -> Self

Performs the conversion.

impl PartialEq<Value> for Value

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

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

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

This method tests for !=.

impl PartialEq<str> for Value

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<&'a str> for Value

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<Value> for str

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<Value> for &'a str

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<String> for Value

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<Value> for String

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<i8> for Value

fn eq(&self, other: &i8) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<Value> for i8

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<i8> for &'a Value

fn eq(&self, other: &i8) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<i8> for &'a mut Value

fn eq(&self, other: &i8) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<i16> for Value

fn eq(&self, other: &i16) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<Value> for i16

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<i16> for &'a Value

fn eq(&self, other: &i16) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<i16> for &'a mut Value

fn eq(&self, other: &i16) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<i32> for Value

fn eq(&self, other: &i32) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<Value> for i32

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<i32> for &'a Value

fn eq(&self, other: &i32) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<i32> for &'a mut Value

fn eq(&self, other: &i32) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<i64> for Value

fn eq(&self, other: &i64) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<Value> for i64

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<i64> for &'a Value

fn eq(&self, other: &i64) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<i64> for &'a mut Value

fn eq(&self, other: &i64) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<u8> for Value

fn eq(&self, other: &u8) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<Value> for u8

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<u8> for &'a Value

fn eq(&self, other: &u8) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<u8> for &'a mut Value

fn eq(&self, other: &u8) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<u16> for Value

fn eq(&self, other: &u16) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<Value> for u16

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<u16> for &'a Value

fn eq(&self, other: &u16) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<u16> for &'a mut Value

fn eq(&self, other: &u16) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<u32> for Value

fn eq(&self, other: &u32) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<Value> for u32

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<u32> for &'a Value

fn eq(&self, other: &u32) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<u32> for &'a mut Value

fn eq(&self, other: &u32) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<u64> for Value

fn eq(&self, other: &u64) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<Value> for u64

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<u64> for &'a Value

fn eq(&self, other: &u64) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<u64> for &'a mut Value

fn eq(&self, other: &u64) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<f32> for Value

fn eq(&self, other: &f32) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<Value> for f32

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<f32> for &'a Value

fn eq(&self, other: &f32) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<f32> for &'a mut Value

fn eq(&self, other: &f32) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<f64> for Value

fn eq(&self, other: &f64) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<Value> for f64

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<f64> for &'a Value

fn eq(&self, other: &f64) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<f64> for &'a mut Value

fn eq(&self, other: &f64) -> bool

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<bool> for Value

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialEq<Value> for bool

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<bool> for &'a Value

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<'a> PartialEq<bool> for &'a mut Value

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

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

#[must_use] fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl Clone for Value

fn clone(&self) -> Value

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Display for Value

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

Display an S-expression value as a string.

let value = sexp!(((city "London") (street "10 Downing Street")));

// Compact format:
//
// ((city "London") (street "10 Downing Street"))
let compact = format!("{}", value);
assert_eq!(compact,
    r#"((city "London") (street "10 Downing Street"))"#);

impl Debug for Value

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

Formats the value using the given formatter.

impl FromStr for Value

type Err = Error

Parse an S-expression value from a string.

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

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

impl<I> Index<I> for Value where
    I: Index, 

type Output = Value

The returned type after indexing.

fn index(&self, index: I) -> &Value

Index into a lexpr::Value using the syntax value[0] or value["k"].

Returns the nil value if the type of self does not match the type of the index, for example if the index is a string and self is not an association list. Also returns the nil value if the given key does not exist in the assication list or the given index is not within the bounds of the list.

Note that repeatedly indexing with a string is not possible, as the indexing operation returns the found association list entry, which is not an association list itself. This behavior, i.e. returning the whole entry including the key is due to the design decison of representing lists as Rust vectors.

Examples

let data = sexp!(((a . 42) (x . (y (z zz)))));

assert_eq!(data["x"], sexp!((y (z zz))));

assert_eq!(data["a"], sexp!(42)); // returns nil for undefined values
assert_eq!(data["b"], sexp!(#nil)); // does not panic