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    100

    use alloc::{string::String, vec::Vec};

    use core::fmt;
    #[cfg(feature = "std")]
    use std::error;

    #[derive(Debug)]
    pub struct Error(String);

    impl fmt::Display for Error {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            write!(f, "{}", self.0)
        }
    }

    #[cfg(feature = "std")]
    impl error::Error for Error {
        fn description(&self) -> &str {
            &self.0
        }
    }

    /// Stack with limit.
    #[derive(Debug)]
    pub struct StackWithLimit<T>
    where
        T: Clone,
    {
        /// Stack values.
        values: Vec<T>,
        /// Stack limit (maximal stack len).
        limit: usize,
    }

    impl<T> StackWithLimit<T>
    where
        T: Clone,
    {
        pub fn with_limit(limit: usize) -> Self {
            StackWithLimit {
                values: Vec::new(),
                limit: limit,
            }
        }

        pub fn is_empty(&self) -> bool {
            self.values.is_empty()
        }

        pub fn len(&self) -> usize {
            self.values.len()
        }

        pub fn top(&self) -> Result<&T, Error> {
            self.values
                .last()
                .ok_or_else(|| Error("non-empty stack expected".into()))
        }

        pub fn top_mut(&mut self) -> Result<&mut T, Error> {
            self.values
                .last_mut()
                .ok_or_else(|| Error("non-empty stack expected".into()))
        }

        pub fn get(&self, index: usize) -> Result<&T, Error> {
            if index >= self.values.len() {
                return Err(Error(format!(
                    "trying to get value at position {} on stack of size {}",
                    index,
                    self.values.len()
                )));
            }

            Ok(self
                .values
                .get(self.values.len() - 1 - index)
                .expect("checked couple of lines above"))
        }

        pub fn push(&mut self, value: T) -> Result<(), Error> {
            if self.values.len() >= self.limit {
                return Err(Error(format!("exceeded stack limit {}", self.limit)));
            }

            self.values.push(value);
            Ok(())
        }

        pub fn pop(&mut self) -> Result<T, Error> {
            self.values
                .pop()
                .ok_or_else(|| Error("non-empty stack expected".into()))
        }

        pub fn resize(&mut self, new_size: usize, dummy: T) {
            debug_assert!(new_size <= self.values.len());
            self.values.resize(new_size, dummy);
        }
    }

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