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//! Provides parsers for f-exps.
use nom::branch::alt;
use nom::bytes::complete::tag;
use nom::character::complete::multispace1;
use nom::combinator::map;
use nom::sequence::{preceded, terminated};
use nom::Parser;
use crate::parsers::prefix_expr;
use crate::parsers::{parse_f_exp, ParseResult, Span};
use crate::types::TimedFluentExpression;
/// Parses an f-exp-t.
///
/// ## Example
/// ```
/// # use pddl::parsers::{parse_f_exp, parse_f_exp_t, preamble::*};
/// # use pddl::{BinaryOp, FluentExpression, TimedFluentExpression, FunctionHead, FunctionSymbol, MultiOp, Term, Variable};
/// assert!(parse_f_exp_t("#t").is_value(TimedFluentExpression::Now));
///
/// assert!(parse_f_exp_t("(* (fuel ?tank) #t)").is_value(
/// TimedFluentExpression::scaled(
/// FluentExpression::function(
/// FunctionHead::with_terms(
/// FunctionSymbol::string("fuel"),
/// [Term::Variable(Variable::string("tank"))]
/// )
/// )
/// )
/// ));
///
/// assert!(parse_f_exp_t("(* #t (fuel ?tank))").is_value(
/// TimedFluentExpression::scaled(
/// FluentExpression::function(
/// FunctionHead::with_terms(
/// FunctionSymbol::string("fuel"),
/// [Term::Variable(Variable::string("tank"))]
/// )
/// )
/// )
/// ));
///```
pub fn parse_f_exp_t<'a, T: Into<Span<'a>>>(input: T) -> ParseResult<'a, TimedFluentExpression> {
let now = map(tag("#t"), |_| TimedFluentExpression::new());
let scaled = map(
prefix_expr(
"*",
alt((
preceded((tag("#t"), multispace1), parse_f_exp),
terminated(parse_f_exp, (multispace1, tag("#t"))),
)),
),
TimedFluentExpression::new_scaled,
);
alt((scaled, now)).parse(input.into())
}
impl crate::parsers::Parser for TimedFluentExpression {
type Item = TimedFluentExpression;
/// See [`parse_f_exp_t`].
fn parse<'a, S: Into<Span<'a>>>(input: S) -> ParseResult<'a, Self::Item> {
parse_f_exp_t(input)
}
}
#[cfg(test)]
mod tests {
use crate::parsers::UnwrapValue;
use crate::{
FluentExpression, FunctionHead, FunctionSymbol, Parser, Term, TimedFluentExpression,
Variable,
};
#[test]
fn test_parse() {
assert!(TimedFluentExpression::parse("#t").is_value(TimedFluentExpression::Now));
assert!(
TimedFluentExpression::parse("(* (fuel ?tank) #t)").is_value(
TimedFluentExpression::scaled(FluentExpression::function(
FunctionHead::with_terms(
FunctionSymbol::string("fuel"),
[Term::Variable(Variable::string("tank"))]
)
))
)
);
assert!(
TimedFluentExpression::parse("(* #t (fuel ?tank))").is_value(
TimedFluentExpression::scaled(FluentExpression::function(
FunctionHead::with_terms(
FunctionSymbol::string("fuel"),
[Term::Variable(Variable::string("tank"))]
)
))
)
);
}
}