just/src/expression.rs

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use super::*;
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/// An expression. Note that the Just language grammar has both an `expression`
/// production of additions (`a + b`) and values, and a `value` production of
/// all other value types (for example strings, function calls, and
/// parenthetical groups).
///
/// The parser parses both values and expressions into `Expression`s.
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#[derive(PartialEq, Debug, Clone)]
pub(crate) enum Expression<'src> {
/// `contents`
Backtick {
contents: String,
token: Token<'src>,
},
/// `name(arguments)`
Call { thunk: Thunk<'src> },
/// `lhs + rhs`
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Concatenation {
lhs: Box<Expression<'src>>,
rhs: Box<Expression<'src>>,
},
/// `if lhs == rhs { then } else { otherwise }`
Conditional {
lhs: Box<Expression<'src>>,
rhs: Box<Expression<'src>>,
then: Box<Expression<'src>>,
otherwise: Box<Expression<'src>>,
operator: ConditionalOperator,
},
/// `(contents)`
Group { contents: Box<Expression<'src>> },
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/// `lhs / rhs`
Join {
lhs: Option<Box<Expression<'src>>>,
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rhs: Box<Expression<'src>>,
},
/// `"string_literal"` or `'string_literal'`
StringLiteral { string_literal: StringLiteral<'src> },
/// `variable`
Variable { name: Name<'src> },
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}
impl<'src> Expression<'src> {
pub(crate) fn variables<'expression>(&'expression self) -> Variables<'expression, 'src> {
Variables::new(self)
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}
}
impl<'src> Display for Expression<'src> {
fn fmt(&self, f: &mut Formatter) -> Result<(), fmt::Error> {
match self {
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Expression::Backtick { token, .. } => write!(f, "{}", token.lexeme()),
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Expression::Join { lhs: None, rhs } => write!(f, "/ {rhs}"),
Expression::Join {
lhs: Some(lhs),
rhs,
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} => write!(f, "{lhs} / {rhs}"),
Expression::Concatenation { lhs, rhs } => write!(f, "{lhs} + {rhs}"),
Expression::Conditional {
lhs,
rhs,
then,
otherwise,
operator,
} => write!(
f,
"if {lhs} {operator} {rhs} {{ {then} }} else {{ {otherwise} }}"
),
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Expression::StringLiteral { string_literal } => write!(f, "{string_literal}"),
Expression::Variable { name } => write!(f, "{}", name.lexeme()),
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Expression::Call { thunk } => write!(f, "{thunk}"),
Expression::Group { contents } => write!(f, "({contents})"),
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}
}
}
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impl<'src> Serialize for Expression<'src> {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: Serializer,
{
match self {
Self::Backtick { contents, .. } => {
let mut seq = serializer.serialize_seq(None)?;
seq.serialize_element("evaluate")?;
seq.serialize_element(contents)?;
seq.end()
}
Self::Call { thunk } => thunk.serialize(serializer),
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Self::Concatenation { lhs, rhs } => {
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let mut seq = serializer.serialize_seq(None)?;
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seq.serialize_element("concatenate")?;
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seq.serialize_element(lhs)?;
seq.serialize_element(rhs)?;
seq.end()
}
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Self::Join { lhs, rhs } => {
let mut seq = serializer.serialize_seq(None)?;
seq.serialize_element("join")?;
seq.serialize_element(lhs)?;
seq.serialize_element(rhs)?;
seq.end()
}
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Self::Conditional {
lhs,
rhs,
then,
otherwise,
operator,
} => {
let mut seq = serializer.serialize_seq(None)?;
seq.serialize_element("if")?;
seq.serialize_element(&operator.to_string())?;
seq.serialize_element(lhs)?;
seq.serialize_element(rhs)?;
seq.serialize_element(then)?;
seq.serialize_element(otherwise)?;
seq.end()
}
Self::Group { contents } => contents.serialize(serializer),
Self::StringLiteral { string_literal } => string_literal.serialize(serializer),
Self::Variable { name } => {
let mut seq = serializer.serialize_seq(None)?;
seq.serialize_element("variable")?;
seq.serialize_element(name)?;
seq.end()
}
}
}
}