From 4430580412af1d03006e87308a501063fc3246b1 Mon Sep 17 00:00:00 2001
From: Tangent Wantwight <tangent128@gmail.com>
Date: Sat, 29 Jul 2023 01:13:38 -0400
Subject: [PATCH] Add AtLeast to Peg helpers
---
peg.js | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git a/peg.js b/peg.js
index 0b82fe7..55d8a8a 100644
--- a/peg.js
+++ b/peg.js
@@ -35,6 +35,7 @@ var Peg = {
},
/**
+ * Creates a pattern that tries the given patterns, in order, until it finds one that matches at the current index.
* @template T
* @param {...Peg.Pattern<T>} patterns
* @return {Peg.Pattern<T>}
@@ -52,6 +53,10 @@ var Peg = {
},
/**
+ * Creates a pattern that concatenates the given patterns, returning a tuple of their captured values.
+ *
+ * For example, if A matches "a" and captures 1, while B matches "b" and captures null,
+ * then `Sequence(A,B)` will match "ab" and capture [1, null]
* @template {unknown[]} T
* @param {{[K in keyof T]: Peg.Pattern<T[K]>}} patterns
* @return {Peg.Pattern<T>}
@@ -70,4 +75,35 @@ var Peg = {
return [values, index];
};
},
+
+ /**
+ * Creates a pattern that matches consecutive runs of the given pattern, returning an array of all captures.
+ *
+ * The match only succeeds if the run is at least {min} instances long.
+ *
+ * If the given pattern does not consume input, the matching will be terminated to prevent an eternal loop.
+ *
+ * Note that if the minimum run is zero, this pattern will always succeed, but might not consume any input.
+ * @template {unknown[]} T
+ * @param {number} min
+ * @param {Peg.Pattern<T>} pattern
+ * @return {Peg.Pattern<T[]>}
+ */
+ AtLeast(min, pattern) {
+ return function (source, index) {
+ const values = /** @type {T[]} */ ([]);
+ do {
+ const match = pattern(source, index);
+ if (match == null) break;
+ values.push(match[0]);
+ if (index == match[1]) break;
+ index = match[1];
+ } while (true);
+ if (values.length >= min) {
+ return [values, index];
+ } else {
+ return null;
+ }
+ };
+ },
};