diff options
author | Nadrieril | 2019-03-01 17:28:19 +0100 |
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committer | Nadrieril | 2019-03-01 17:28:19 +0100 |
commit | e5d9aee00b0c775df1d8e2d8819aeb80dffa73c2 (patch) | |
tree | e763a24a0d635048232e72e167ca37eafec69369 /src/context.rs | |
parent | 8a2b7536902831079eddd7b00291b718f5dd7186 (diff) |
Split abnf_to_pest and dhall into their own crates
Diffstat (limited to 'src/context.rs')
-rw-r--r-- | src/context.rs | 51 |
1 files changed, 0 insertions, 51 deletions
diff --git a/src/context.rs b/src/context.rs deleted file mode 100644 index c2e1913..0000000 --- a/src/context.rs +++ /dev/null @@ -1,51 +0,0 @@ -use std::collections::HashMap; - -/// A `(Context a)` associates `Text` labels with values of type `a` -/// -/// The `Context` is used for type-checking when `(a = Expr X)` -/// -/// * You create a `Context` using `empty` and `insert` -/// * You transform a `Context` using `fmap` -/// * You consume a `Context` using `lookup` and `toList` -/// -/// The difference between a `Context` and a `Map` is that a `Context` lets you -/// have multiple ordered occurrences of the same key and you can query for the -/// `n`th occurrence of a given key. -/// -#[derive(Debug, Clone)] -pub struct Context<'i, T>(HashMap<&'i str, Vec<T>>); - -impl<'i, T> Context<'i, T> { - /// An empty context with no key-value pairs - pub fn new() -> Self { - Context(HashMap::new()) - } - - /// Look up a key by name and index - /// - /// ```c - /// lookup _ _ empty = Nothing - /// lookup k 0 (insert k v c) = Just v - /// lookup k n (insert k v c) = lookup k (n - 1) c -- 1 <= n - /// lookup k n (insert j v c) = lookup k n c -- k /= j - /// ``` - pub fn lookup<'a>(&'a self, k: &str, n: usize) -> Option<&'a T> { - self.0.get(k).and_then(|v| v.get(v.len() - 1 - n)) - } - - pub fn map<U, F: Fn(&T) -> U>(&self, f: F) -> Context<'i, U> { - Context(self.0.iter().map(|(k, v)| (*k, v.iter().map(&f).collect())).collect()) - } -} - -impl<'i, T: Clone> Context<'i, T> { - /// Add a key-value pair to the `Context` - pub fn insert(&self, k: &'i str, v: T) -> Self { - let mut ctx = (*self).clone(); - { - let m = ctx.0.entry(k).or_insert_with(Vec::new); - m.push(v); - } - ctx - } -} |