Enum lambda_calculus::term::Term

pub enum Term {
    Var(usize),
    Abs(Box<Term>),
    App(Box<Term>, Box<Term>),
}

A lambda term that is either a variable with a De Bruijn index, an abstraction over a term or an applicaction of one term to another.

Variants

Var(usize)

a variable

Abs(Box<Term>)

an abstraction

App(Box<Term>, Box<Term>)

an application

Methods

impl Term

fn app(self, argument: Term) -> Term

Applies self to another term without substitution or reduction.

Example

use lambda_calculus::term::*;

assert_eq!(Var(1).app(Var(2)), App(Box::new(Var(1)), Box::new(Var(2))));

fn unvar(self) -> Result<usize, Error>

Consumes a lambda variable and returns its De Bruijn index.

Example

use lambda_calculus::term::*;

assert_eq!(Var(1).unvar(), Ok(1));

Errors

The function will return an error if self is not a Variable.

fn unvar_ref(&self) -> Result<&usize, Error>

Returns a reference to a variable's index.

Example

use lambda_calculus::term::*;

assert_eq!(Var(1).unvar_ref(), Ok(&1));

Errors

The function will return an error if self is not a Variable.

fn unvar_mut(&mut self) -> Result<&mut usize, Error>

Returns a mutable reference to a variable's index.

Example

use lambda_calculus::term::*;

assert_eq!(Var(1).unvar_mut(), Ok(&mut 1));

Errors

The function will return an error if self is not a Variable.

fn unabs(self) -> Result<Term, Error>

Consumes an abstraction and returns its underlying term.

Example

use lambda_calculus::term::*;

assert_eq!(abs(Var(1)).unabs(), Ok(Var(1)));

Errors

The function will return an error if self is not an Abstraction.

fn unabs_ref(&self) -> Result<&Term, Error>

Returns a reference to an abstraction's underlying term.

Example

use lambda_calculus::term::*;

assert_eq!(abs(Var(1)).unabs_ref(), Ok(&Var(1)));

Errors

The function will return an error if self is not an Abstraction.

fn unabs_mut(&mut self) -> Result<&mut Term, Error>

Returns a mutable reference to an abstraction's underlying term.

Example

use lambda_calculus::term::*;

assert_eq!(abs(Var(1)).unabs_mut(), Ok(&mut Var(1)));

Errors

The function will return an error if self is not an Abstraction.

fn unapp(self) -> Result<(Term, Term), Error>

Consumes an application and returns a pair containing its underlying terms.

Example

use lambda_calculus::term::*;

assert_eq!(app(Var(1), Var(2)).unapp(), Ok((Var(1), Var(2))));

Errors

The function will return an error if self is not an Application.

fn unapp_ref(&self) -> Result<(&Term, &Term), Error>

Returns a pair containing references to an application's underlying terms.

Example

use lambda_calculus::term::*;

assert_eq!(app(Var(1), Var(2)).unapp_ref(), Ok((&Var(1), &Var(2))));

Errors

The function will return an error if self is not an Application.

fn unapp_mut(&mut self) -> Result<(&mut Term, &mut Term), Error>

Returns a pair containing mutable references to an application's underlying terms.

Example

use lambda_calculus::term::*;

assert_eq!(app(Var(1), Var(2)).unapp_mut(), Ok((&mut Var(1), &mut Var(2))));

Errors

The function will return an error if self is not an Application.

fn lhs(self) -> Result<Term, Error>

Returns the left-hand side term of an application. Consumes self.

Example

use lambda_calculus::term::*;

assert_eq!(Var(1).app(Var(2)).lhs(), Ok(Var(1)));

Errors

The function will return an error if self is not an Application.

fn lhs_ref(&self) -> Result<&Term, Error>

Returns a reference to the left-hand side term of an application.

Example

use lambda_calculus::term::*;

assert_eq!(app(Var(1), Var(2)).lhs_ref(), Ok(&Var(1)));

Errors

The function will return an error if self is not an Application.

fn lhs_mut(&mut self) -> Result<&mut Term, Error>

Returns a mutable reference to the left-hand side term of an application.

Example

use lambda_calculus::term::*;

assert_eq!(app(Var(1), Var(2)).lhs_mut(), Ok(&mut Var(1)));

fn rhs(self) -> Result<Term, Error>

Returns the right-hand side term of an application. Consumes self.

Example

use lambda_calculus::term::*;

assert_eq!(app(Var(1), Var(2)).rhs(), Ok(Var(2)));

Errors

The function will return an error if self is not an Application.

fn rhs_ref(&self) -> Result<&Term, Error>

Returns a reference to the right-hand side term of an application.

Example

use lambda_calculus::term::*;

assert_eq!(app(Var(1), Var(2)).rhs_ref(), Ok(&Var(2)));

Errors

The function will return an error if self is not an Application.

fn rhs_mut(&mut self) -> Result<&mut Term, Error>

Returns a mutable reference to the right-hand side term of an application.

Example

use lambda_calculus::term::*;

assert_eq!(app(Var(1), Var(2)).rhs_mut(), Ok(&mut Var(2)));

Errors

The function will return an error if self is not an Application.

impl Term

fn apply(self, rhs: &Term) -> Result<Term, Error>

Applies self to another Term and performs substitution, consuming self in the process.

Example

use lambda_calculus::parser::*;

let lhs    = parse(&"λλ42(λ13)", DeBruijn).unwrap();
let rhs    = parse(&"λ51", DeBruijn).unwrap();
let result = parse(&"λ3(λ61)(λ1(λ71))", DeBruijn).unwrap();

assert_eq!(lhs.apply(&rhs), Ok(result));

Errors

The function will return an error if self is not an Abstraction.

fn eval(self) -> Result<Term, Error>

Reduces an Application by substitution and variable update.

Example

use lambda_calculus::*;
use lambda_calculus::combinators::i;

assert_eq!(app(i(), Var(1)).eval(), Ok(Var(1)));

Errors

The function will return an error if self is not an Application or if its left hand side term is not an Abstraction.

fn beta(&mut self, order: Order, limit: usize, verbose: bool) -> usize

Performs β-reduction on a Term with the specified evaluation Order, an optional limit on number of reductions (0 means no limit) and optional display of reduction steps; it returns the number of performed reductions.

Example

use lambda_calculus::*;

let expression = parse(&"(λa.λb.λc.b (a b c)) (λa.λb.b)", Classic);
let reduced    = parse(&"λa.λb.a b", Classic);

assert!(expression.is_ok());
assert!(reduced.is_ok());

let mut expression = expression.unwrap();
expression.beta(NOR, 0, false);

assert_eq!(expression, reduced.unwrap());

impl Term

fn value(&self) -> Result<usize, Error>

Returns the value of self if it's a Church-encoded number.

Example

use lambda_calculus::*;

assert_eq!(Term::from(1).value(), Ok(1));

Errors

The function will return an error if self is not a Church number.

fn is_cnum(&self) -> bool

Checks whether self is a Church-encoded number.

Example

use lambda_calculus::*;

assert!(Term::from(1).is_cnum());
assert!(!Var(1).is_cnum());
assert!(!Term::from(true).is_cnum(), false);

impl Term

fn is_pair(&self) -> bool

Checks whether self is a Church-encoded pair.

Example

use lambda_calculus::*;

assert!(Term::from((1.into(), 2.into())).is_pair());

fn unpair(self) -> Result<(Term, Term), Error>

Splits a Church-encoded pair into a pair of terms, consuming self.

Example

use lambda_calculus::*;

assert_eq!(
    Term::from((1.into(), 2.into())).unpair(),
    Ok((1.into(), 2.into()))
);

Errors

The function will return an error if self is not a Church pair.

fn unpair_ref(&self) -> Result<(&Term, &Term), Error>

Splits a Church-encoded pair into a pair of references to its underlying terms.

Example

use lambda_calculus::*;

assert_eq!(
    Term::from((1.into(), 2.into())).unpair_ref(),
    Ok((&1.into(), &2.into()))
);

Errors

The function will return an error if self is not a Church pair.

fn unpair_mut(&mut self) -> Result<(&mut Term, &mut Term), Error>

Splits a Church-encoded pair into a pair of mutable references to its underlying terms.

Example

use lambda_calculus::*;

assert_eq!(
    Term::from((1.into(), 2.into())).unpair_mut(),
    Ok((&mut 1.into(), &mut 2.into()))
);

Errors

The function will return an error if self is not a Church pair.

fn fst(self) -> Result<Term, Error>

Returns the first term from a Church-encoded pair, consuming self.

Example

use lambda_calculus::*;

assert_eq!(Term::from((1.into(), 2.into())).fst(), Ok(1.into()));

Errors

The function will return an error if self is not a Church pair.

fn fst_ref(&self) -> Result<&Term, Error>

Returns a reference to the first term of a Church-encoded pair.

Example

use lambda_calculus::*;

assert_eq!(Term::from((1.into(), 2.into())).fst_ref(), Ok(&1.into()));

Errors

The function will return an error if self is not a Church pair.

fn fst_mut(&mut self) -> Result<&mut Term, Error>

Returns a mutable reference to the first term of a Church-encoded pair. Returns a reference to the first term of a Church-encoded pair.

Example

use lambda_calculus::*;

assert_eq!(Term::from((1.into(), 2.into())).fst_mut(), Ok(&mut 1.into()));

Errors

The function will return an error if self is not a Church pair.

fn snd(self) -> Result<Term, Error>

Returns the second term from a Church-encoded pair, consuming self.

Example

use lambda_calculus::*;

assert_eq!(Term::from((1.into(), 2.into())).snd(), Ok(2.into()));

Errors

The function will return an error if self is not a Church pair.

fn snd_ref(&self) -> Result<&Term, Error>

Returns a reference to the second term of a Church-encoded pair.

Example

use lambda_calculus::*;

assert_eq!(Term::from((1.into(), 2.into())).snd_ref(), Ok(&2.into()));

Errors

The function will return an error if self is not a Church pair.

fn snd_mut(&mut self) -> Result<&mut Term, Error>

Returns a mutable reference to the second term of a Church-encoded pair.

Example

use lambda_calculus::*;

assert_eq!(Term::from((1.into(), 2.into())).snd_mut(), Ok(&mut 2.into()));

Errors

The function will return an error if self is not a Church pair.

impl Term

fn is_empty(&self) -> bool

Checks whether self is a empty Church list, i.e. nil().

Example

use lambda_calculus::church::lists::nil;

assert!(nil().is_empty());

fn is_list(&self) -> bool

Checks whether self is a Church list.

Example

use lambda_calculus::*;

assert!(Term::from(vec![1.into(), 2.into(), 3.into()]).is_list());

fn uncons(self) -> Result<(Term, Term), Error>

Splits a Church list into a pair containing its first term and a list of all the other terms, consuming self.

Example

use lambda_calculus::*;

assert_eq!(
    Term::from(vec![1.into(), 2.into(), 3.into()]).uncons(),
    Ok((1.into(), vec![2.into(), 3.into()].into()))
);

Errors

The function will return an error if self is not a Church list.

fn uncons_ref(&self) -> Result<(&Term, &Term), Error>

Splits a Church list into a pair containing references to its first term and a to list of all the other terms.

Example

use lambda_calculus::*;

assert_eq!(
    Term::from(vec![1.into(), 2.into(), 3.into()]).uncons_ref(),
    Ok((&1.into(), &vec![2.into(), 3.into()].into()))
);

Errors

The function will return an error if self is not a Church list.

fn uncons_mut(&mut self) -> Result<(&mut Term, &mut Term), Error>

Splits a Church list into a pair containing mutable references to its first term and a to list of all the other terms.

Example

use lambda_calculus::*;

assert_eq!(
    Term::from(vec![1.into(), 2.into(), 3.into()]).uncons_mut(),
    Ok((&mut 1.into(), &mut vec![2.into(), 3.into()].into()))
);

Errors

The function will return an error if self is not a Church list.

fn head(self) -> Result<Term, Error>

Returns the first term from a Church list, consuming self.

Example

use lambda_calculus::*;

assert_eq!(
    Term::from(vec![1.into(), 2.into(), 3.into()]).head(),
    Ok(1.into())
);

Errors

The function will return an error if self is not a Church list.

fn head_ref(&self) -> Result<&Term, Error>

Returns a reference to the first term of a Church list.

Example

use lambda_calculus::*;

assert_eq!(
    Term::from(vec![1.into(), 2.into(), 3.into()]).head_ref(),
    Ok(&1.into())
);

Errors

The function will return an error if self is not a Church list.

fn head_mut(&mut self) -> Result<&mut Term, Error>

Returns a mutable reference to the first term of a Church list.

Example

use lambda_calculus::*;

assert_eq!(
    Term::from(vec![1.into(), 2.into(), 3.into()]).head_mut(),
    Ok(&mut 1.into())
);

Errors

The function will return an error if self is not a Church list.

fn tail(self) -> Result<Term, Error>

Returns a list of all the terms of a Church list but the first one, consuming self.

Example

use lambda_calculus::*;

assert_eq!(
    Term::from(vec![1.into(), 2.into(), 3.into()]).tail(),
    Ok(vec![2.into(), 3.into()].into())
);

Errors

The function will return an error if self is not a Church list.

fn tail_ref(&self) -> Result<&Term, Error>

Returns a reference to a list of all the terms of a Church list but the first one.

Example

use lambda_calculus::*;

assert_eq!(
    Term::from(vec![1.into(), 2.into(), 3.into()]).tail_ref(),
    Ok(&vec![2.into(), 3.into()].into())
);

Errors

The function will return an error if self is not a Church list.

fn tail_mut(&mut self) -> Result<&mut Term, Error>

Returns a mutable reference to a list of all the terms of a Church list but the first one.

Example

use lambda_calculus::*;

assert_eq!(
    Term::from(vec![1.into(), 2.into(), 3.into()]).tail_mut(),
    Ok(&mut vec![2.into(), 3.into()].into())
);

Errors

The function will return an error if self is not a Church list.

fn len(&self) -> Result<usize, Error>

Returns the length of a Church list

Example

use lambda_calculus::*;

assert_eq!(Term::from(vec![1.into(), 2.into(), 3.into()]).len(), Ok(3));

Errors

The function will return an error if self is not a Church list.

fn push(self, term: Term) -> Result<Term, Error>

Adds a term to the beginning of a Church list and returns the new list. Consumes self and the argument.

Example

use lambda_calculus::*;

let list_from_vec = Term::from(vec![1.into(), 2.into(), 3.into()]);
let list_pushed = Term::from(vec![])
                  .push(3.into())
                  .and_then(|t| t.push(2.into()))
                  .and_then(|t| t.push(1.into()))
                  .unwrap();

assert_eq!(list_from_vec, list_pushed);

Errors

The function will return an error if self is not a Church list or a nil().

fn pop(&mut self) -> Result<Term, Error>

Removes the first element from a Church list and returns it.

Example

use lambda_calculus::*;

let mut list = Term::from(vec![1.into(), 2.into(), 3.into()]);

assert_eq!(list.pop(), Ok(1.into()));
assert_eq!(list, vec![2.into(), 3.into()].into());
assert_eq!(list.pop(), Ok(2.into()));
assert_eq!(list, vec![3.into()].into());
assert_eq!(list.pop(), Ok(3.into()));
assert_eq!(list, vec![].into());

assert!(list.is_empty())

Errors

The function will return an error if self is not a Church list.

Trait Implementations

impl PartialEq for Term

fn eq(&self, __arg_0: &Term) -> bool

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

fn ne(&self, __arg_0: &Term) -> bool

This method tests for !=.

impl Clone for Term

fn clone(&self) -> Term

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Hash for Term

fn hash<__H: Hasher>(&self, __arg_0: &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 Eq for Term

impl Display for Term

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

Formats the value using the given formatter.

impl Debug for Term

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

Formats the value using the given formatter.

impl From<usize> for Term

fn from(n: usize) -> Self

Performs the conversion.

impl From<bool> for Term

fn from(b: bool) -> Self

Performs the conversion.

impl From<(Term, Term)> for Term

fn from((t1, t2): (Term, Term)) -> Self

Performs the conversion.

impl From<Vec<Term>> for Term

fn from(terms: Vec<Term>) -> Self

Performs the conversion.

impl Iterator for Term

type Item = Term

The type of the elements being iterated over.

fn next(&mut self) -> Option<Term>

Advances the iterator and returns the next value.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the iterator.

fn count(self) -> usize

Consumes the iterator, counting the number of iterations and returning it.

fn last(self) -> Option<Self::Item>

Consumes the iterator, returning the last element.

fn nth(&mut self, n: usize) -> Option<Self::Item>

Returns the nth element of the iterator.

fn step_by(self, step: usize) -> StepBy<Self>

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

unstable replacement of Range::step_by

Creates an iterator starting at the same point, but stepping by the given amount at each iteration.

fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter> where
    U: IntoIterator<Item = Self::Item>, 

Takes two iterators and creates a new iterator over both in sequence.

fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter> where
    U: IntoIterator, 

'Zips up' two iterators into a single iterator of pairs.

fn map<B, F>(self, f: F) -> Map<Self, F> where
    F: FnMut(Self::Item) -> B, 

Takes a closure and creates an iterator which calls that closure on each element.

fn for_each<F>(self, f: F) where
    F: FnMut(Self::Item) -> (), 

Calls a closure on each element of an iterator.

fn filter<P>(self, predicate: P) -> Filter<Self, P> where
    P: FnMut(&Self::Item) -> bool, 

Creates an iterator which uses a closure to determine if an element should be yielded.

fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where
    F: FnMut(Self::Item) -> Option<B>, 

Creates an iterator that both filters and maps.

fn enumerate(self) -> Enumerate<Self>

Creates an iterator which gives the current iteration count as well as the next value.

fn peekable(self) -> Peekable<Self>

Creates an iterator which can use peek to look at the next element of the iterator without consuming it.

fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where
    P: FnMut(&Self::Item) -> bool, 

Creates an iterator that [skip]s elements based on a predicate.

fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where
    P: FnMut(&Self::Item) -> bool, 

Creates an iterator that yields elements based on a predicate.

fn skip(self, n: usize) -> Skip<Self>

Creates an iterator that skips the first n elements.

fn take(self, n: usize) -> Take<Self>

Creates an iterator that yields its first n elements.

fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> where
    F: FnMut(&mut St, Self::Item) -> Option<B>, 

An iterator adaptor similar to [fold] that holds internal state and produces a new iterator.

fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> where
    F: FnMut(Self::Item) -> U,
    U: IntoIterator, 

Creates an iterator that works like map, but flattens nested structure.

fn fuse(self) -> Fuse<Self>

Creates an iterator which ends after the first [None].

fn inspect<F>(self, f: F) -> Inspect<Self, F> where
    F: FnMut(&Self::Item) -> (), 

Do something with each element of an iterator, passing the value on.

fn by_ref(&mut self) -> &mut Self

Borrows an iterator, rather than consuming it.

fn collect<B>(self) -> B where
    B: FromIterator<Self::Item>, 

Transforms an iterator into a collection.

fn partition<B, F>(self, f: F) -> (B, B) where
    B: Default + Extend<Self::Item>,
    F: FnMut(&Self::Item) -> bool, 

Consumes an iterator, creating two collections from it.

fn fold<B, F>(self, init: B, f: F) -> B where
    F: FnMut(B, Self::Item) -> B, 

An iterator adaptor that applies a function, producing a single, final value.

fn all<F>(&mut self, f: F) -> bool where
    F: FnMut(Self::Item) -> bool, 

Tests if every element of the iterator matches a predicate.

fn any<F>(&mut self, f: F) -> bool where
    F: FnMut(Self::Item) -> bool, 

Tests if any element of the iterator matches a predicate.

fn find<P>(&mut self, predicate: P) -> Option<Self::Item> where
    P: FnMut(&Self::Item) -> bool, 

Searches for an element of an iterator that satisfies a predicate.

fn position<P>(&mut self, predicate: P) -> Option<usize> where
    P: FnMut(Self::Item) -> bool, 

Searches for an element in an iterator, returning its index.

fn rposition<P>(&mut self, predicate: P) -> Option<usize> where
    P: FnMut(Self::Item) -> bool,
    Self: ExactSizeIterator + DoubleEndedIterator, 

Searches for an element in an iterator from the right, returning its index.

fn max(self) -> Option<Self::Item> where
    Self::Item: Ord, 

Returns the maximum element of an iterator.

fn min(self) -> Option<Self::Item> where
    Self::Item: Ord, 

Returns the minimum element of an iterator.

fn max_by_key<B, F>(self, f: F) -> Option<Self::Item> where
    B: Ord,
    F: FnMut(&Self::Item) -> B, 

Returns the element that gives the maximum value from the specified function.

fn max_by<F>(self, compare: F) -> Option<Self::Item> where
    F: FnMut(&Self::Item, &Self::Item) -> Ordering, 

Returns the element that gives the maximum value with respect to the specified comparison function.

fn min_by_key<B, F>(self, f: F) -> Option<Self::Item> where
    B: Ord,
    F: FnMut(&Self::Item) -> B, 

Returns the element that gives the minimum value from the specified function.

fn min_by<F>(self, compare: F) -> Option<Self::Item> where
    F: FnMut(&Self::Item, &Self::Item) -> Ordering, 

Returns the element that gives the minimum value with respect to the specified comparison function.

fn rev(self) -> Rev<Self> where
    Self: DoubleEndedIterator, 

Reverses an iterator's direction.

fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where
    FromA: Default + Extend<A>,
    FromB: Default + Extend<B>,
    Self: Iterator<Item = (A, B)>, 

Converts an iterator of pairs into a pair of containers.

fn cloned<'a, T>(self) -> Cloned<Self> where
    Self: Iterator<Item = &'a T>,
    T: 'a + Clone, 

Creates an iterator which [clone]s all of its elements.

fn cycle(self) -> Cycle<Self> where
    Self: Clone, 

Repeats an iterator endlessly.

fn sum<S>(self) -> S where
    S: Sum<Self::Item>, 

Sums the elements of an iterator.

fn product<P>(self) -> P where
    P: Product<Self::Item>, 

Iterates over the entire iterator, multiplying all the elements

fn cmp<I>(self, other: I) -> Ordering where
    I: IntoIterator<Item = Self::Item>,
    Self::Item: Ord, 

Lexicographically compares the elements of this Iterator with those of another.

fn partial_cmp<I>(self, other: I) -> Option<Ordering> where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Lexicographically compares the elements of this Iterator with those of another.

fn eq<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialEq<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are equal to those of another.

fn ne<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialEq<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are unequal to those of another.

fn lt<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are lexicographically less than those of another.

fn le<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are lexicographically less or equal to those of another.

fn gt<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are lexicographically greater than those of another.

fn ge<I>(self, other: I) -> bool where
    I: IntoIterator,
    Self::Item: PartialOrd<<I as IntoIterator>::Item>, 

Determines if the elements of this Iterator are lexicographically greater than or equal to those of another.

impl Index<usize> for Term

type Output = Term

The returned type after indexing.

fn index(&self, i: usize) -> &Self::Output

Performs the indexing (container[index]) operation.

impl From<Option<Term>> for Term

fn from(option: Option<Term>) -> Self

Performs the conversion.