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//! Provides parsers for derived predicates.
use nom::character::complete::multispace1;
use nom::combinator::map;
use nom::sequence::{preceded, tuple};
use crate::parsers::{parse_atomic_formula_skeleton, parse_gd};
use crate::parsers::{prefix_expr, ParseResult, Span};
use crate::types::DerivedPredicate;
/// Parses a derived predicate, i.e. `(:derived <atomic formula skeleton> <GD>)`.
///
/// ## Example
/// ```
/// # use pddl::parsers::{parse_derived_predicate, preamble::*};
/// # use pddl::GoalDefinition;
/// let input = r#"(:derived (train-usable ?t - train)
/// (and
/// (train-has-guard ?t)
/// (train-has-driver ?t)
/// )
/// )"#;
///
/// let (remaining, predicate) = parse_derived_predicate(input).unwrap();
/// assert_eq!(predicate.predicate().name(), "train-usable");
/// assert!(matches!(predicate.expression(), &GoalDefinition::And(..)));
///```
pub fn parse_derived_predicate<'a, T: Into<Span<'a>>>(
input: T,
) -> ParseResult<'a, DerivedPredicate> {
map(
prefix_expr(
":derived",
tuple((
parse_atomic_formula_skeleton,
preceded(multispace1, parse_gd),
)),
),
DerivedPredicate::from,
)(input.into())
}
impl crate::parsers::Parser for DerivedPredicate {
type Item = DerivedPredicate;
/// See [`parse_derived_predicate`].
fn parse<'a, S: Into<Span<'a>>>(input: S) -> ParseResult<'a, Self::Item> {
parse_derived_predicate(input)
}
}
#[cfg(test)]
mod tests {
use crate::{DerivedPredicate, GoalDefinition, Parser};
#[test]
fn test_parse() {
let input = r#"(:derived (train-usable ?t - train)
(and
(train-has-guard ?t)
(train-has-driver ?t)
)
)"#;
let (_, predicate) = DerivedPredicate::parse(input).unwrap();
assert_eq!(predicate.predicate().name(), "train-usable");
assert!(matches!(predicate.expression(), &GoalDefinition::And(..)));
}
}