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use std::fmt;
#[derive(Debug)]
pub enum Error {
Syntax {
exp: String,
},
Type {
expected: &'static str,
given: String,
},
UndefinedSymbol {
sym: String,
},
Arity {
expected: usize,
given: usize,
},
ArityMin {
expected: usize,
given: usize,
},
ArityMax {
expected: usize,
given: usize,
},
NotAList {
atom: String,
},
NullList,
NotAProcedure {
exp: String,
},
Index {
i: usize,
},
IO(::std::fmt::Error),
}
impl ::std::error::Error for Error {}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
Error::Syntax { exp } => write!(f, "Could not parse expression: {}", exp),
Error::Type { expected, given } => {
write!(f, "Type error: expected {}, got {}", expected, given)
}
Error::UndefinedSymbol { sym } => write!(f, "Undefined symbol: {}", sym),
Error::Arity { expected, given } => write!(
f,
"Arity mismatch: expected {} parameters, got {}.",
expected, given
),
Error::ArityMin { expected, given } => write!(
f,
"Arity mismatch: expected at least {} parameters, got {}.",
expected, given
),
Error::ArityMax { expected, given } => write!(
f,
"Arity mismatch: expected at most {} parameters, got {}.",
expected, given
),
Error::NotAList { atom } => write!(f, "Expected a list, got {}", atom),
Error::NullList => write!(f, "Expected a pair, got null."),
Error::NotAProcedure { exp } => write!(f, "{} is not a procedure.", exp),
Error::Index { i } => write!(f, "Tried to access invalid index: [{}]", i),
Error::IO(err) => write!(f, "I/O error: {}", err),
}
}
}