Editorial: make gb18030 math more clear

Fixes #63.

Overview.html

@@ -9,7 +9,7 @@
 
 <p><a class="logo" href="https://whatwg.org/"><img alt="WHATWG" height="100" src="https://resources.whatwg.org/logo-encoding.svg" width="100"></a></p>
 <h1>Encoding</h1>
-<h2 class="no-num no-toc" id="living-standard-—-last-updated-29-july-2016">Living Standard — Last Updated 29 July 2016</h2>
+<h2 class="no-num no-toc" id="living-standard-—-last-updated-4-august-2016">Living Standard — Last Updated 4 August 2016</h2>
 
 <dl>
  <dt>Participate:
@@ -1732,7 +1732,9 @@ <h4 id="gb18030-decoder"><span class="secno">11.2.1 </span><dfn>gb18030 decoder<
    <li><p>If <var>byte</var> is in the range 0x30 to 0x39, inclusive, set
    <var>code point</var> to the
    <a href="#index-gb18030-ranges-code-point">index gb18030 ranges code point</a> for
-   (((<a href="#gb18030-first">gb18030 first</a> − 0x81) × 10 + <a href="#gb18030-second">gb18030 second</a> − 0x30) × 126 + <a href="#gb18030-third">gb18030 third</a> − 0x81) × 10 + <var>byte</var> − 0x30.
+   ((<a href="#gb18030-first">gb18030 first</a> − 0x81) × (10 × 126 × 10)) +
+   ((<a href="#gb18030-second">gb18030 second</a> − 0x30) × (10 × 126)) +
+   ((<a href="#gb18030-third">gb18030 third</a> − 0x81) × 10) + <var>byte</var> − 0x30.
 
    <li><p>Let <var>buffer</var> be a byte sequence consisting of
    <a href="#gb18030-second">gb18030 second</a>, <a href="#gb18030-third">gb18030 third</a>, and <var>byte</var>, in
@@ -1851,20 +1853,17 @@ <h4 id="gb18030-encoder"><span class="secno">11.2.2 </span><dfn>gb18030 encoder<
  <li><p>Set <var>pointer</var> to the
  <a href="#index-gb18030-ranges-pointer">index gb18030 ranges pointer</a> for <var>code point</var>.
 
- <li><p>Let <var>byte1</var> be floor(<var>pointer</var> / 10 / 126 / 10).
+ <li><p>Let <var>byte1</var> be floor(<var>pointer</var> / (10 × 126 × 10)).
 
- <li><p>Set <var>pointer</var> to
- <var>pointer</var> − <var>byte1</var> × 10 × 126 × 10.
+ <li><p>Set <var>pointer</var> to <var>pointer</var> % (10 × 126 × 10).
 
- <li><p>Let <var>byte2</var> be floor(<var>pointer</var> / 10 / 126).
+ <li><p>Let <var>byte2</var> be floor(<var>pointer</var> / (10 × 126)).
 
- <li><p>Set <var>pointer</var> to
- <var>pointer</var> − <var>byte2</var> × 10 × 126.
+ <li><p>Set <var>pointer</var> to <var>pointer</var> % (10 × 126).
 
  <li><p>Let <var>byte3</var> be floor(<var>pointer</var> / 10).
 
- <li><p>Let <var>byte4</var> be
- <var>pointer</var> − <var>byte3</var> × 10.
+ <li><p>Let <var>byte4</var> be <var>pointer</var> % 10.
 
  <li><p>Return four bytes whose values are <var>byte1</var> + 0x81,
  <var>byte2</var> + 0x30, <var>byte3</var> + 0x81,

Overview.src.html

@@ -1649,7 +1649,9 @@ <h4><dfn>gb18030 decoder</dfn></h4>
    <li><p>If <var>byte</var> is in the range 0x30 to 0x39, inclusive, set
    <var>code point</var> to the
    <span>index gb18030 ranges code point</span> for
-   (((<span>gb18030 first</span> &minus; 0x81) &times; 10 + <span>gb18030 second</span> &minus; 0x30) &times; 126 + <span>gb18030 third</span> &minus; 0x81) &times; 10 + <var>byte</var> &minus; 0x30.
+   ((<span>gb18030 first</span> &minus; 0x81) &times; (10 &times; 126 &times; 10)) +
+   ((<span>gb18030 second</span> &minus; 0x30) &times; (10 &times; 126)) +
+   ((<span>gb18030 third</span> &minus; 0x81) &times; 10) + <var>byte</var> &minus; 0x30.
 
    <li><p>Let <var>buffer</var> be a byte sequence consisting of
    <span>gb18030 second</span>, <span>gb18030 third</span>, and <var>byte</var>, in
@@ -1768,20 +1770,17 @@ <h4><dfn>gb18030 encoder</dfn></h4>
  <li><p>Set <var>pointer</var> to the
  <span>index gb18030 ranges pointer</span> for <var>code point</var>.
 
- <li><p>Let <var>byte1</var> be floor(<var>pointer</var> / 10 / 126 / 10).
+ <li><p>Let <var>byte1</var> be floor(<var>pointer</var> / (10 &times; 126 &times; 10)).
 
- <li><p>Set <var>pointer</var> to
- <var>pointer</var> &minus; <var>byte1</var> &times; 10 &times; 126 &times; 10.
+ <li><p>Set <var>pointer</var> to <var>pointer</var> % (10 &times; 126 &times; 10).
 
- <li><p>Let <var>byte2</var> be floor(<var>pointer</var> / 10 / 126).
+ <li><p>Let <var>byte2</var> be floor(<var>pointer</var> / (10 &times; 126)).
 
- <li><p>Set <var>pointer</var> to
- <var>pointer</var> &minus; <var>byte2</var> &times; 10 &times; 126.
+ <li><p>Set <var>pointer</var> to <var>pointer</var> % (10 &times; 126).
 
  <li><p>Let <var>byte3</var> be floor(<var>pointer</var> / 10).
 
- <li><p>Let <var>byte4</var> be
- <var>pointer</var> &minus; <var>byte3</var> &times; 10.
+ <li><p>Let <var>byte4</var> be <var>pointer</var> % 10.
 
  <li><p>Return four bytes whose values are <var>byte1</var> + 0x81,
  <var>byte2</var> + 0x30, <var>byte3</var> + 0x81,