rust/src/lambda.rs


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use std::{
    fmt::{self, Display},
    fs::read_to_string,
};

pub fn run(arg: &str) -> String {
    let content = read_to_string(arg).unwrap();
    let result = interpret(&content.to_string());

    result.to_string()
}

#[derive(Debug, PartialEq)]
pub enum Value {
    Num(i32),
}

impl Display for Value {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Value::Num(i) => write!(f, "{}", i),
        }
    }
}

fn interpret(arg: &str) -> Value {
    Value::Num(arg.parse().unwrap())
}

#[cfg(test)]
mod tests {
    use super::interpret;
    use super::Value::Num;
    // Bring the macros and other important things into scope.
    use proptest::prelude::*;

    proptest! {
        #[test]
        fn interpret_integer_as_number(i in -1000i32..1000) {
            let result = interpret(&i.to_string());
            assert_eq!(Num(i), result);
        }
    }
}