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//! Provides parsers for literals.
use nom::branch::alt;
use nom::combinator::map;
use nom::Parser;
use crate::parsers::prefix_expr;
use crate::parsers::{atomic_formula, ParseError, Span};
use crate::types::Literal;
/// Parser combinator that parses a literal, i.e. `<atomic formula(t)> | (not <atomic formula(t)>)`.
///
/// ## Example
/// ```
/// # use nom::character::complete::alpha1;
/// # use nom::Parser;
/// # use pddl::parsers::{literal, parse_name, preamble::*};
/// # use pddl::{AtomicFormula, EqualityAtomicFormula, PredicateAtomicFormula, Predicate, Literal};
/// assert!(literal(parse_name).parse(Span::new("(= x y)")).is_value(
/// Literal::AtomicFormula(
/// AtomicFormula::Equality(
/// EqualityAtomicFormula::new(
/// "x".into(),
/// "y".into()
/// )
/// )
/// )
/// ));
/// assert!(literal(parse_name).parse(Span::new("(not (= x y))")).is_value(
/// Literal::NotAtomicFormula(
/// AtomicFormula::Equality(
/// EqualityAtomicFormula::new(
/// "x".into(),
/// "y".into()
/// )
/// )
/// )
/// ));
/// ```
pub fn literal<'a, F, O>(
inner: F,
) -> impl Parser<Span<'a>, Output = Literal<O>, Error = ParseError<'a>>
where
F: Clone + Parser<Span<'a>, Output = O, Error = ParseError<'a>>,
{
let is = map(atomic_formula(inner.clone()), |af| Literal::new(af));
let is_not = map(prefix_expr("not", atomic_formula(inner)), |af| {
Literal::new_not(af)
});
alt((is_not, is))
}
#[cfg(test)]
mod tests {
use crate::parsers::{literal, parse_name, Span, UnwrapValue};
use crate::{AtomicFormula, EqualityAtomicFormula, Literal};
use nom::Parser;
#[test]
fn test_parse() {
assert!(literal(parse_name)
.parse(Span::new("(= x y)"))
.is_value(Literal::AtomicFormula(AtomicFormula::Equality(
EqualityAtomicFormula::new("x".into(), "y".into())
))));
assert!(literal(parse_name)
.parse(Span::new("(not (= x y))"))
.is_value(Literal::NotAtomicFormula(AtomicFormula::Equality(
EqualityAtomicFormula::new("x".into(), "y".into())
))));
}
}