Enum Index

pub enum Index {
    Num(usize),
    Next,
}

Represents an abstract index into an array.

If provided an upper bound with Self::for_len or Self::for_len_incl, will produce a concrete numerical index.

Variants

Num(usize)

A non-negative integer value

Next

The - token, the position of the next would-be item in the array

Implementations

impl Index

pub fn for_len(&self, length: usize) -> Result<usize, OutOfBoundsError>

Bounds the index for a given array length (exclusive).

The upper range is exclusive, so only indices that are less than the given length will be accepted as valid. This ensures that the resolved numerical index can be used to access an existing array element.

Self::Next, by consequence, is always considered invalid, since it resolves to the array length itself.

See also Self::for_len_incl for an alternative if you wish to accept Self::Next (or its numerical equivalent) as valid.

Examples

assert_eq!(Index::Num(0).for_len(1), Ok(0));
assert!(Index::Num(1).for_len(1).is_err());
assert!(Index::Next.for_len(1).is_err());

Errors

Returns OutOfBoundsError if the index is out of bounds.

pub fn for_len_incl(&self, length: usize) -> Result<usize, OutOfBoundsError>

Bounds the index for a given array length (inclusive).

The upper range is inclusive, so an index pointing to the position after the last element will be considered valid. Be careful when using the resulting numerical index for accessing an array.

Self::Next is always considered valid.

See also Self::for_len for an alternative if you wish to ensure that the resolved index can be used to access an existing array element.

Examples

assert_eq!(Index::Num(1).for_len_incl(1), Ok(1));
assert_eq!(Index::Next.for_len_incl(1), Ok(1));
assert!(Index::Num(2).for_len_incl(1).is_err());

Errors

Returns OutOfBoundsError if the index is out of bounds.

pub fn for_len_unchecked(&self, length: usize) -> usize

Resolves the index for a given array length.

No bound checking will take place. If you wish to ensure the index can be used to access an existing element in the array, use Self::for_len - or use Self::for_len_incl if you wish to accept Self::Next as valid as well.

Examples

assert_eq!(Index::Num(42).for_len_unchecked(30), 42);
assert_eq!(Index::Next.for_len_unchecked(30), 30);

// no bounds checks
assert_eq!(Index::Num(34).for_len_unchecked(40), 34);
assert_eq!(Index::Next.for_len_unchecked(34), 34);

Trait Implementations

impl Clone for Index

fn clone(&self) -> Index

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Index

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

Formats the value using the given formatter.

impl Display for Index

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

Formats the value using the given formatter.

impl From<usize> for Index

fn from(value: usize) -> Self

Converts to this type from the input type.

impl FromStr for Index

type Err = ParseIndexError

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 Index

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, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for Index

fn cmp(&self, other: &Index) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

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

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for Index

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for Index

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

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

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

Tests less than (for self and other) and is used by the < operator.

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

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

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

Tests greater than (for self and other) and is used by the > operator.

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

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

impl TryFrom<&String> for Index

type Error = ParseIndexError

The type returned in the event of a conversion error.

fn try_from(value: &String) -> Result<Self, Self::Error>

Performs the conversion.

impl TryFrom<&Token<'_>> for Index

type Error = ParseIndexError

The type returned in the event of a conversion error.

fn try_from(value: &Token<'_>) -> Result<Self, Self::Error>

Performs the conversion.

impl TryFrom<&str> for Index

type Error = ParseIndexError

The type returned in the event of a conversion error.

fn try_from(value: &str) -> Result<Self, Self::Error>

Performs the conversion.

impl TryFrom<String> for Index

type Error = ParseIndexError

The type returned in the event of a conversion error.

fn try_from(value: String) -> Result<Self, Self::Error>

Performs the conversion.

impl TryFrom<Token<'_>> for Index

type Error = ParseIndexError

The type returned in the event of a conversion error.

fn try_from(value: Token<'_>) -> Result<Self, Self::Error>

Performs the conversion.

impl Copy for Index

impl Eq for Index

impl StructuralPartialEq for Index