docs(core): added an example of pattern use

harper-core/src/patterns/is_not_title_case.rs

@@ -2,8 +2,8 @@ use crate::{make_title_case, Dictionary, Token, TokenStringExt};
 
 use super::Pattern;
 
-/// Will match full length of wrapped pattern __only if the matched
-/// text is not already title case__.
+/// Will match full length of wrapped pattern only if the matched
+/// text is not already title case.
 pub struct IsNotTitleCase<D: Dictionary> {
     inner: Box<dyn Pattern>,
     dict: D,

harper-core/src/patterns/mod.rs

@@ -1,3 +1,10 @@
+//! [`Pattern`]s are one of the more powerful constructs inside Harper, especially for beginners.
+//!
+//! Through the [`PatternLinter`](crate::linting::PatternLinter) trait, they make it much easier to
+//! build Harper [rules](crate::linting::Linter).
+//!
+//! See the page about [`SequencePattern`] for a concrete example of their use.
+
 use std::collections::VecDeque;
 
 use crate::{Document, Span, Token, VecExt};
@@ -127,7 +134,7 @@ where
     }
 }
 
-trait DocPattern {
+pub trait DocPattern {
     fn find_all_matches_in_doc(&self, document: &Document) -> Vec<Span>;
 }
 

harper-core/src/patterns/sequence_pattern.rs

@@ -6,6 +6,26 @@ use super::{NounPhrase, Pattern, RepeatingPattern, WordSet};
 use crate::{CharStringExt, Lrc, Token, TokenKind};
 
 /// A pattern that checks that a sequence of other patterns match.
+/// There are specific extension methods available, but you can also use [`Self::then`] to add
+/// arbitrary patterns.
+///
+/// ## Example
+///
+/// Let's say we wanted to locate places in a [`Document`] where an article is followed by a noun.
+/// We can do that with a `SequencePattern`.
+///
+/// ```rust
+/// use harper_core::patterns::{SequencePattern, DocPattern};
+/// use harper_core::{Document, Span};
+///
+/// let document = Document::new_markdown_default_curated("This is a test.");
+///
+/// let pattern = SequencePattern::default().then_article().then_whitespace().then_noun();
+/// let matches = pattern.find_all_matches_in_doc(&document);
+///
+/// // The pattern found that the tokens at indexes 4, 5, and 6 fit the criteria.
+/// assert_eq!(matches, vec![Span::new(4, 7)]);
+/// ```
 #[derive(Default)]
 pub struct SequencePattern {
     token_patterns: Vec<Box<dyn Pattern>>,
@@ -60,6 +80,7 @@ impl SequencePattern {
     gen_then_from_is!(adjective);
     gen_then_from_is!(apostrophe);
     gen_then_from_is!(hyphen);
+    gen_then_from_is!(article);
 
     pub fn then_word_set(self, set: WordSet) -> Self {
         self.then(Box::new(set))