# mod.rs - source
Source of the Rust file `maplibre/src/render/util/mod.rs`.
Keywords: rust, rustlang, rust-lang

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    use std::cmp::Ordering;
    use std::mem;

    /// A wrapper type that enables ordering floats. This is a work around for the famous "rust float
    /// ordering" problem. By using it, you acknowledge that sorting NaN is undefined according to spec.
    /// This implementation treats NaN as the "smallest" float.
    #[derive(Debug, Copy, Clone, PartialOrd)]
    pub struct FloatOrd(pub f32);

    impl PartialEq for FloatOrd {
        fn eq(&self, other: &Self) -> bool {
            if self.0.is_nan() && other.0.is_nan() {
                true
            } else {
                self.0 == other.0
            }
        }
    }

    impl Eq for FloatOrd {}

    #[allow(clippy::derive_ord_xor_partial_ord)]
    impl Ord for FloatOrd {
        fn cmp(&self, other: &Self) -> Ordering {
            self.0.partial_cmp(&other.0).unwrap_or_else(|| {
                if self.0.is_nan() && !other.0.is_nan() {
                    Ordering::Less
                } else if !self.0.is_nan() && other.0.is_nan() {
                    Ordering::Greater
                } else {
                    Ordering::Equal
                }
            })
        }
    }

    /// Wrapper around a resource which can be initialized or uninitialized.
    /// Uninitialized resourced can be initialized by calling [`Eventually::initialize()`].
    pub enum Eventually<T> {
        Initialized(T),
        Uninitialized,
    }

    pub trait HasChanged {
        type Criteria: Eq;

        fn has_changed(&self, criteria: &Self::Criteria) -> bool;
    }

    impl<T> HasChanged for Option<T>
    where
        T: HasChanged,
    {
        type Criteria = T::Criteria;

        fn has_changed(&self, criteria: &Self::Criteria) -> bool {
            match self {
                None => true,
                Some(value) => value.has_changed(criteria),
            }
        }
    }

    impl<'a, T> Eventually<T>
    where
        T: HasChanged,
    {
        #[tracing::instrument(name = "reinitialize", skip_all)]
        pub fn reinitialize(&mut self, f: impl FnOnce() -> T, criteria: &T::Criteria) {
            let should_replace = match &self {
                Eventually::Initialized(current) => {
                    if current.has_changed(criteria) {
                        true
                    } else {
                        false
                    }
                }
                Eventually::Uninitialized => true,
            };

            if should_replace {
                *self = Eventually::Initialized(f());
            }
        }
    }
    impl<T> Eventually<T> {
        #[tracing::instrument(name = "initialize", skip_all)]
        pub fn initialize(&mut self, f: impl FnOnce() -> T) {
            if let Eventually::Uninitialized = self {
                *self = Eventually::Initialized(f());
            }
        }

        pub fn take(&mut self) -> Eventually<T> {
            mem::replace(self, Eventually::Uninitialized)
        }
    }

    impl<T> Default for Eventually<T> {
        fn default() -> Self {
            Eventually::Uninitialized
        }
    }