File 0277-Correct-some-details-in-the-operator-table.patch of Package erlang
From e91f8ddc34b7dd8a8c21bc4b3664c902857b4c98 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Thu, 15 Dec 2022 09:41:15 +0100
Subject: [PATCH] Correct some details in the operator table
* Change "priority" to the standard terminology "precedence".
* Document the changed precedence of the `catch` operator.
* Mention the restrictions of `?=` in a note after the operand table.
* Mark the non-associative binary operators as such in the operand table.
---
system/doc/reference_manual/expressions.xml | 64 +++++++++++++++------
1 file changed, 46 insertions(+), 18 deletions(-)
diff --git a/system/doc/reference_manual/expressions.xml b/system/doc/reference_manual/expressions.xml
index 341fa32432..5b96c50065 100644
--- a/system/doc/reference_manual/expressions.xml
+++ b/system/doc/reference_manual/expressions.xml
@@ -1491,10 +1491,26 @@ catch Expr</code>
returns the value <c>Any</c>.</p>
<p><em>Example:</em></p>
<pre>
-5> <input>catch throw(hello).</input>
+3> <input>catch throw(hello).</input>
hello</pre>
<p>If <c>throw/1</c> is not evaluated within a catch, a
<c>nocatch</c> run-time error occurs.</p>
+
+ <p>Before Erlang/OTP 24, the <c>catch</c> operator had
+ the lowest precedence, making it necessary to add parentheses when
+ combining it with the <c>match</c> operator:</p>
+ <pre>
+1> <input>A = (catch 42).</input>
+42
+2> <input>A.</input>
+42</pre>
+
+ <p>Starting from Erlang/OTP 24, the parentheses can be omitted:</p>
+ <pre>
+1> <input>A = catch 42.</input>
+42
+2> <input>A.</input>
+42</pre>
</section>
<section>
@@ -1951,7 +1968,7 @@ end</pre>
<section>
<marker id="prec"></marker>
<title>Operator Precedence</title>
- <p>Operator precedence in falling priority:</p>
+ <p>Operator precedence in descending order:</p>
<table>
<row>
<cell align="left" valign="middle">:</cell>
@@ -1967,53 +1967,61 @@ end</pre>
</row>
<row>
<cell align="left" valign="middle">/ * div rem band and</cell>
- <cell align="left" valign="middle">Left associative</cell>
+ <cell align="left" valign="middle">Left-associative</cell>
</row>
<row>
<cell align="left" valign="middle">+ - bor bxor bsl bsr or xor</cell>
- <cell align="left" valign="middle">Left associative</cell>
+ <cell align="left" valign="middle">Left-associative</cell>
</row>
<row>
<cell align="left" valign="middle">++ --</cell>
- <cell align="left" valign="middle">Right associative</cell>
+ <cell align="left" valign="middle">Right-associative</cell>
</row>
<row>
<cell align="left" valign="middle">== /= =< < >= > =:= =/=</cell>
- <cell align="left" valign="middle"> </cell>
+ <cell align="left" valign="middle">Non-associative</cell>
</row>
<row>
<cell align="left" valign="middle">andalso</cell>
- <cell align="left" valign="middle"> </cell>
+ <cell align="left" valign="middle">Left-associative</cell>
</row>
<row>
<cell align="left" valign="middle">orelse</cell>
+ <cell align="left" valign="middle">Left-associative</cell>
+ </row>
+ <row>
+ <cell align="left" valign="middle">catch</cell>
<cell align="left" valign="middle"> </cell>
</row>
<row>
<cell align="left" valign="middle">= !</cell>
- <cell align="left" valign="middle">Right associative</cell>
+ <cell align="left" valign="middle">Right-associative</cell>
</row>
<row>
<cell align="left" valign="middle">?=</cell>
- <cell align="left" valign="middle"> </cell>
- </row>
- <row>
- <cell align="left" valign="middle">catch</cell>
- <cell align="left" valign="middle"> </cell>
+ <cell align="left" valign="middle">Non-associative</cell>
</row>
<tcaption>Operator Precedence</tcaption>
</table>
+ <p>Before Erlang/OTP 24, the <c>catch</c> operator had the lowest
+ precedence.</p>
<p>When evaluating an expression, the operator with the highest
- priority is evaluated first. Operators with the same priority
- are evaluated according to their associativity.</p>
- <p><em>Example:</em></p>
- <p>The left associative arithmetic operators are evaluated left to
+ precedence is evaluated first. Operators with the same precedence
+ are evaluated according to their associativity. Non-associative
+ operators cannot be combined with operators of the same precedence.</p>
+ <p><em>Examples:</em></p>
+ <p>The left-associative arithmetic operators are evaluated left to
right:</p>
<pre>
<input>6 + 5 * 4 - 3 / 2</input> evaluates to
<input>6 + 20 - 1.5</input> evaluates to
<input>26 - 1.5</input> evaluates to
<input>24.5</input></pre>
+
+<p>The non-associative operators cannot be combined:</p>
+ <pre>
+1> <input>1 < X < 10.</input>
+* 1:7: syntax error before: '<'</pre>
</section>
</chapter>
--
2.35.3
