From ee0f9a79fdf01b45509a16ce58f07a7a67af6350 Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonyg@leastfixedpoint.com>
Date: Sun, 29 Oct 2023 14:51:03 +0100
Subject: [PATCH] Ignore leading/trailing/repeated slashes and ampersands.
 Closes #32.

---
 preserves-schema.md | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/preserves-schema.md b/preserves-schema.md
index 9f42fc4..eb5dbda 100644
--- a/preserves-schema.md
+++ b/preserves-schema.md
@@ -4,7 +4,7 @@ title: "Preserves Schema"
 ---
 
 Tony Garnock-Jones <tonyg@leastfixedpoint.com>  
-February 2023. Version 0.3.1.
+February 2023. Version 0.3.2.
 
   [abnf]: https://tools.ietf.org/html/rfc7405
 
@@ -189,12 +189,14 @@ with algebraic data types would produce a labelled-sum-of-products type.
 
 ### Alternation definitions.
 
-    OrPattern = AltPattern "/" AltPattern *("/" AltPattern)
+    OrPattern = [orsep] AltPattern 1*(orsep AltPattern) [orsep]
+        orsep = 1*"/"
 
-The right-hand-side of a definition may supply two or more
-*alternatives*. When parsing, the alternatives are tried in order; the
-result of the first successful alternative is the result of the entire
-parse.
+The right-hand-side of a definition may supply two or more *alternatives*.
+Alternatives are separated by any number of slashes `/`, and leading or
+trailing slashes are ignored. When parsing, the alternatives are tried in
+order; the result of the first successful alternative is the result of the
+entire parse.
 
 **Host-language types.** The type corresponding to an `OrPattern` is an
 algebraic sum type, a union type, a variant type, or a concrete subclass
@@ -223,13 +225,15 @@ there is any).
 
 ### Intersection definitions.
 
-    AndPattern = NamedPattern "&" NamedPattern *("&" NamedPattern)
+    AndPattern = [andsep] NamedPattern 1*(andsep NamedPattern) [andsep]
+        andsep = 1*"&"
 
 The right-hand-side of a definition may supply two or more patterns, the
 *intersection* of whose denotations is the denotation of the overall
-definition. When parsing, every pattern is tried: if all succeed, the
-resulting information is combined into a single type; otherwise, the
-overall parse fails.
+definition. The patterns are separated by any number of ampersands `&`,
+and leading or trailing ampersands are ignored. When parsing, every
+pattern is tried: if all succeed, the resulting information is combined
+into a single type; otherwise, the overall parse fails.
 
 When serializing, the terms resulting from serializing at each pattern
 are *merged* together.