From 71ce36141aaacfa714edca2e408ca522a3bc5554 Mon Sep 17 00:00:00 2001
From: Marshall Lochbaum <mwlochbaum@gmail.com>
Date: Mon, 17 Oct 2022 21:55:50 -0400
Subject: =?UTF-8?q?Specify=20scalar=20extension=20for=20=E2=80=A2bit=20ope?=
 =?UTF-8?q?rations?=
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---
 docs/spec/system.html | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

(limited to 'docs')

diff --git a/docs/spec/system.html b/docs/spec/system.html
index d889019d..5e076378 100644
--- a/docs/spec/system.html
+++ b/docs/spec/system.html
@@ -692,9 +692,15 @@
 <td>integer</td>
 <td><code><span class='Function'>×</span></code></td>
 </tr>
+<tr>
+<td><code><span class='Modifier'>_cast</span></code></td>
+<td>1</td>
+<td>any</td>
+<td>identity</td>
+</tr>
 </tbody>
 </table>
-<p>An operation is exposed as a 1-modifier that takes up to four numbers for its operand.</p>
+<p>The <code><span class='Modifier'>_cast</span></code> modifier is special and not considered an operation; see below. Each operation is exposed as a 1-modifier that takes up to four numbers for its operand.</p>
 <ul>
 <li>Operation width</li>
 <li>Result element width</li>
@@ -742,5 +748,5 @@
 </tr>
 </tbody>
 </table>
-<p>An argument must be an array of numbers or an array of characters. Its elements must fit into the appropriate type. The &quot;cell size&quot; is the length in bits of a 1-cell, that is, <code><span class='Value'>width</span><span class='Function'>×</span><span class='Number'>¯1</span><span class='Function'>⊑</span><span class='Number'>1</span><span class='Function'>∾≢</span><span class='Value'>arg</span></code>, and must be a multiple of the operation width. Both arguments must have the same cell size, and the same leading shape <code><span class='Number'>¯1</span><span class='Function'>↓≢</span><span class='Value'>arg</span></code>. The result shape is this leading shape followed by the cell size divided by the result element width.</p>
+<p>An argument must be an array of numbers or an array of characters. Its elements must fit into the appropriate type. The &quot;cell size&quot; is the length in bits of a 1-cell, that is, <code><span class='Value'>width</span><span class='Function'>×</span><span class='Number'>¯1</span><span class='Function'>⊑</span><span class='Number'>1</span><span class='Function'>∾≢</span><span class='Value'>arg</span></code>, and must be a multiple of the operation width. The &quot;leading shape&quot; is <code><span class='Number'>¯1</span><span class='Function'>↓≢</span><span class='Value'>arg</span></code>. For two-argument functions one argument can be scalar-extended if it has rank 1 and cell size equal to the operation width. Otherwise both arguments must have the same cell size, and the same leading shape. The result shape is the leading shape of any non-extended argument followed by its cell size divided by the result element width. As a scalar-extended argument indicates a single operation input, it's reused every time the operation is applied.</p>
 <p>Another tool is provided for performing direct conversions, with no operation applied. The 1-modifier <code><span class='Value'>•bit.</span><span class='Modifier'>_cast</span></code> takes a two-element operand and one argument, for example <code><span class='Bracket'>⟨</span><span class='Number'>8</span><span class='Separator'>,</span><span class='Number'>16</span><span class='Ligature'>‿</span><span class='String'>'c'</span><span class='Bracket'>⟩</span><span class='Value'>•bit.</span><span class='Modifier'>_cast</span> <span class='Value'>ints</span></code> to convert each pair of numbers in <code><span class='Value'>ints</span></code> into a 2-byte character. Each element of <code><span class='Value'>𝕗</span></code> is a number or number-character pair giving width and type. The argument is encoded according to the first and decoded according to the second.</p>
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