53 lines
1.7 KiB
Rust
53 lines
1.7 KiB
Rust
//! Scope, a type that represents the locality of a variable.
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use std::{
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cmp::Ordering,
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fmt::{self, Display, Formatter},
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};
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use serde::{Deserialize, Serialize};
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/// Variable locality, as defined by its depth and block index.
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///
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/// The `block index` is a unique identifier for a block within a chunk. It is used to differentiate
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/// between blocks that are not nested together but have the same depth, i.e. sibling scopes. If the
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/// `block_index` is 0, then the scope is the root scope of the chunk. The `block_index` is always 0
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/// when the `depth` is 0. See [Chunk::begin_scope][] and [Chunk::end_scope][] to see how scopes are
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/// incremented and decremented.
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#[derive(Debug, Clone, Copy, Default, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
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pub struct Scope {
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/// Level of block nesting.
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pub depth: u8,
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/// Index of the block in the chunk.
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pub block_index: u8,
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}
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impl Scope {
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pub fn new(depth: u8, block_index: u8) -> Self {
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Self { depth, block_index }
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}
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pub fn contains(&self, other: &Self) -> bool {
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match self.depth.cmp(&other.depth) {
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Ordering::Less => false,
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Ordering::Greater => self.block_index >= other.block_index,
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Ordering::Equal => self.block_index == other.block_index,
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}
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}
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pub fn begin(&mut self, block_index: u8) {
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self.depth += 1;
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self.block_index = block_index;
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}
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pub fn end(&mut self, block_index: u8) {
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self.depth -= 1;
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self.block_index = block_index;
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}
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}
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impl Display for Scope {
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fn fmt(&self, f: &mut Formatter) -> fmt::Result {
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write!(f, "({}, {})", self.depth, self.block_index)
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}
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}
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