Struct parol::analysis::k_tuple::Terminals

pub struct Terminals { /* private fields */ }

A collection of terminals

The terminals are stored in a 128 bit integer where each terminal is stored in a fixed number of bits. The number of bits is determined by the number of terminals to store. The maximum number of terminals when storing MAX_K terminals in 128 bits is: 128 / MAX_K = 128 / 10 = 12.8 => 12 bits The maximum number of terminals that can be stored is 2^12 = 4096. The maximum value of the bit count is therefore 12 and can safely be stored in four bits. We store a mask to more easily extract the terminals from the 128 bits unsigned integer. The mask to extract single terminals from the 128 bit unsigned integer is calculated as 2^bits - 1 that is equivalent to the expression !(!0u128 << bits) at runtime.

Since we use only 120 bits to store the terminals, we have 8 bits left. We use the 8 bits to store the index of the next insertion as well as the bit count used to calculate the mask. Therefore we split the highest 8 bits of the 128 bits unsigned integer as follows:

• The higher 4 bits are used to store the number of bits used per terminal
• The lower 4 bits are used to store the index of the next insertion

Implementations

impl Terminals

pub fn new(max_terminal_index: usize) -> Self

Creates a new item

use parol::analysis::k_tuple::Terminals;
use parol::analysis::compiled_terminal::CompiledTerminal;
let t = Terminals::new(1);
assert!(t.is_empty());
assert_eq!(0, t.len(), "len");
assert_eq!(0, t.k_len(5), "k_len");
assert_eq!(None, t.get(0));
assert_eq!(None, t.get(9));

pub fn eps(max_terminal_index: usize) -> Terminals

Creates a new item with epsilon semantic

use parol::analysis::k_tuple::{Terminals, TerminalMappings};
use parol::analysis::compiled_terminal::CompiledTerminal;
let t = Terminals::eps(1);
assert!(!t.is_empty());
assert_eq!(1, t.len(), "len");
assert_eq!(1, t.k_len(5), "k_len");
assert_eq!(Some(CompiledTerminal::eps()), t.get(0));
assert_eq!(None, t.get(1));
assert_eq!(None, t.get(9));

pub fn end(max_terminal_index: usize) -> Terminals

Creates a new item with end (EOI) semantic Such a terminal can’t be extended, i.e. you can’t append more terminals

use parol::analysis::k_tuple::{Terminals, TerminalMappings};
use parol::analysis::compiled_terminal::CompiledTerminal;
let t = Terminals::end(1);
assert!(!t.is_empty());
assert_eq!(1, t.len());
assert_eq!(1, t.k_len(5));
assert_eq!(Some(CompiledTerminal::end()), t.get(0));
assert_eq!(None, t.get(1));
assert_eq!(None, t.get(9));

pub fn of(k: usize, other: Self) -> Self

Creates a new object with maximum k length from another object

pub fn len(&self) -> usize

Returns the length of the collection

pub fn is_empty(&self) -> bool

Checks if the collection is empty

pub fn next_index(&self) -> u8

Returns the index of the next insertion The highest 8 bits of t are used to store the index of the next insertion in it’s lowest 4 bits.

pub fn inc_index(&mut self)

Increments the index of the next insertion

pub fn bits(&self) -> u8

Returns the bits used per terminal The highest 8 bits of t are used to store the number of bits used per terminal in it’s highest 4 bits.

use parol::analysis::k_tuple::Terminals;
let t = Terminals::eps(1);
assert_eq!(2, t.bits());

pub fn set_bits(&mut self, bits: u8)

Sets the number of bits used per terminal

pub fn mask(&self) -> u128

Returns the mask used to extract the terminal at position i The mask is calculated as 2^bits - 1 that is equivalent to the expression !(!0u128 << bits).

pub fn is_k_complete(&self, k: usize) -> bool

Checks if the collection is k-complete, i.e. no terminals can be added

use parol::analysis::k_tuple::Terminals;
let t = Terminals::end(1);
assert!(t.is_k_complete(5));

pub fn k_len(&self, k: usize) -> usize

Returns the k-length, i.e. the number of symbols that contributes to lookahead sizes

pub fn clear(&mut self)

Clears the collection

pub fn k_concat(self, other: &Self, k: usize) -> Self

Concatenates two collections with respect to the rules of k-concatenation

use parol::analysis::k_tuple::{Terminals, TerminalMappings};
use parol::analysis::compiled_terminal::CompiledTerminal;
let t1 = Terminals::eps(1);
let t2 = Terminals::end(1);
let t = t1.k_concat(&t2, 5);
assert!(t.is_k_complete(5));
assert_eq!(1, t.len());
assert_eq!(Some(CompiledTerminal::end()), t.get(0));
let t = t2.k_concat(&t1, 5);
assert!(t.is_k_complete(5));
assert_eq!(1, t.len());
assert_eq!(Some(CompiledTerminal::end()), t.get(0));
let mut t1 = Terminals::new(6);
t1.extend([1, 2, 3].iter().cloned());
let mut t2 = Terminals::new(6);
t2.extend([4, 5, 6].iter().cloned());
let t = t1.k_concat(&t2, 5);
assert!(t.is_k_complete(5));
assert_eq!(5, t.len());
assert_eq!(Some(CompiledTerminal(1)), t.get(0));
assert_eq!(Some(CompiledTerminal(2)), t.get(1));
assert_eq!(Some(CompiledTerminal(3)), t.get(2));
assert_eq!(Some(CompiledTerminal(4)), t.get(3));
assert_eq!(Some(CompiledTerminal(5)), t.get(4));
assert_eq!(None, t.get(5));

pub fn push(&mut self, t: CompiledTerminal) -> Result<(), String>

Adds a new terminal to self if max size is not reached yet and if last is not EOI

pub fn is_eps(&self) -> bool

Checks if self is an Epsilon

pub fn iter(&self) -> TermIt

Creates an iterator over the terminals

pub fn get(&self, i: usize) -> Option<CompiledTerminal>

Returns the terminal at position i

pub fn set(&mut self, i: usize, t: CompiledTerminal)

Sets the terminal at position i

Trait Implementations

impl Clone for Terminals

fn clone(&self) -> Terminals

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Terminals

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

Formats the value using the given formatter.

impl Default for Terminals

fn default() -> Terminals

Returns the “default value” for a type.

impl Display for Terminals

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

Formats the value using the given formatter.

impl Extend<CompiledTerminal> for Terminals

fn extend<I: IntoIterator<Item = CompiledTerminal>>(&mut self, iter: I)

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements.

impl Extend<u16> for Terminals

fn extend<I: IntoIterator<Item = TerminalIndex>>(&mut self, iter: I)

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements.

impl From<&Terminals> for u128

fn from(t: &Terminals) -> Self

Converts to this type from the input type.

impl Hash for Terminals

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 Terminals

fn cmp(&self, other: &Self) -> 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 + PartialOrd,

Restrict a value to a certain interval.

impl PartialEq for Terminals

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

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

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

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

impl PartialOrd for Terminals

fn partial_cmp(&self, other: &Self) -> 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 Terminals

impl Eq for Terminals

impl StructuralPartialEq for Terminals