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Add split_prefix_suffix helper

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This commit is contained in:
Laurenz 2025-01-23 17:52:18 +01:00
parent 467968af07
commit ab9ba8c387
2 changed files with 29 additions and 9 deletions
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11
crates/typst-layout/src/math/lr.rs
View File

@ -2,6 +2,7 @@ use typst_library::diag::SourceResult;
use typst_library::foundations::{Packed, StyleChain};
use typst_library::layout::{Abs, Axis, Rel};
use typst_library::math::{EquationElem, LrElem, MidElem};
use typst_utils::SliceExt;
use unicode_math_class::MathClass;
use super::{stretch_fragment, MathContext, MathFragment, DELIM_SHORT_FALL};
@ -29,15 +30,7 @@ pub fn layout_lr(
let mut fragments = ctx.layout_into_fragments(body, styles)?;
// Ignore leading and trailing ignorant fragments.
let start_idx = fragments
.iter()
.position(|f| !f.is_ignorant())
.unwrap_or(fragments.len());
let end_idx = fragments
.iter()
.skip(start_idx)
.rposition(|f| !f.is_ignorant())
.map_or(start_idx, |i| start_idx + i + 1);
let (start_idx, end_idx) = fragments.split_prefix_suffix(|f| f.is_ignorant());
let inner_fragments = &mut fragments[start_idx..end_idx];
let axis = scaled!(ctx, styles, axis_height);

27
crates/typst-utils/src/lib.rs
View File

@ -128,6 +128,20 @@ pub trait SliceExt<T> {
where
F: FnMut(&T) -> K,
K: PartialEq;
/// Computes two indices which split a slice into three parts.
///
/// - A prefix which matches `f`
/// - An inner portion
/// - A suffix which matches `f` and does not overlap with the prefix
///
/// If all elements match `f`, the prefix becomes `self` and the suffix
/// will be empty.
///
/// Returns the indices at which the inner portion and the suffix start.
fn split_prefix_suffix<F>(&self, f: F) -> (usize, usize)
where
F: FnMut(&T) -> bool;
}
impl<T> SliceExt<T> for [T] {
@ -157,6 +171,19 @@ impl<T> SliceExt<T> for [T] {
fn group_by_key<K, F>(&self, f: F) -> GroupByKey<'_, T, F> {
GroupByKey { slice: self, f }
}
fn split_prefix_suffix<F>(&self, mut f: F) -> (usize, usize)
where
F: FnMut(&T) -> bool,
{
let start = self.iter().position(|v| !f(v)).unwrap_or(self.len());
let end = self
.iter()
.skip(start)
.rposition(|v| !f(v))
.map_or(start, |i| start + i + 1);
(start, end)
}
}
/// This struct is created by [`SliceExt::group_by_key`].