removed mod operator, restricted / operator

Author: howcom

css3-values/Overview.src.html

@@ -518,6 +518,18 @@ <h4>The 'calc', 'min' and 'max' functions</h4>
 <p>The expression language of these functions is described by
 the grammar and prose below.
 
+<pre>
+S       : calc | min | max;
+calc    : "calc(" S* sum ")" S*;
+min     : "min(" S* sum [ "," S* sum ]* )"" S*;
+max     : "max(" S* sum [ "," S* sum ]* ")" S*;
+sum     : product [ [ "+" | "-" ] S* product ]*;
+product : unit [[ "*" S* unit ] | [ "/" S* NUMBER ]] *;
+unit    : ["+"|"-"]? [ NUMBER S* | DIMENSION S* | PERCENTAGE S* |
+          min | max | "(" S* sum ")" S* ];
+</pre>
+
+<!--
 <pre>
 S       : calc | min | max;
 calc    : "calc(" S* sum ")" S*;
@@ -528,6 +540,8 @@ <h4>The 'calc', 'min' and 'max' functions</h4>
 unit    : ["+"|"-"]? [ NUMBER S* | DIMENSION S* | PERCENTAGE S* |
           min | max | "(" S* sum ")" S* ];
 </pre>
+-->
+
 
 <p>The semantic constraints are as follows: The context of the
 expression imposes a target type, which is one of length, frequency,
@@ -546,75 +560,11 @@ <h4>The 'calc', 'min' and 'max' functions</h4>
 <li>At "*":<br>
   check: at least one side is "number" return: the type of the other side
 <li>At "/":<br> 
-   check: either right side is "number," or both have the same type<br>
-   return: if the former, type of left side; otherwise "number"
-<li>At "mod": <br>
-   check: both sides have the same type<br>
-   return: "number"
+   check: right side is "number"<br>
+   return: the type of the left side
 </ol>
 
 
-<!--
-<p>A value is ignored if a division by zero or other mathematical
- errors occur in the calculation.
-
-<div class="example">
-<p>In this example, the second declaration will be ignored due to a
-division by zero.
-<pre>
-p { 
- margin: 1em;
- margin: calc(1em-2px) calc(1em/0) 
-}
-</pre>
-</div>
-
-<p class=issue>Issue: At a later date new operators such as min/max, conditionals, new constants, division by length units etc. may be added.
-
-
-<p>The expression language is defined by 'length-expression' below:
-
-<pre>
-  &lt;length> := calc( &lt;length-expression> ) | &lt;atomic-length>
-
-  &lt;length-expression> := S* &lt;length-additive-expression> S*
-
-  &lt;length-additive-expression> :=
-     &lt;length-multiplicative-expression> |
-     &lt;length-additive-expression> S+ '+' S+ &lt;length-multiplicative-expression> |
-     &lt;length-additive-expression> S+ '-' S+ &lt;length-multiplicative-expression>
-
-  &lt;length-multiplicative-expression>
-     &lt;length-term> |
-     &lt;length-multiplicative-expression> S* '*' S* &lt;number-term> |
-     &lt;number-multiplicative-expression> S* '*' S* &lt;length-term> |
-     &lt;length-multiplicative-expression> S* '/' S* &lt;number-term> |
-     &lt;length-multiplicative-expression> S+ 'mod' S+ &lt;number-term>
-
-  &lt;length-term> := '(' &lt;length-expression> ')' | &lt;atomic-length>
-
-  &lt;number-additive-expression> :=
-     &lt;number-multiplicative-expression> |
-     &lt;number-additive-expression> S+ '+' S+ &lt;number-multiplicative-expression> |
-     &lt;number-additive-expression> S+ '-' S+ &lt;number-multiplicative-expression>
-
-  &lt;number-multiplicative-expression> :=
-     &lt;number-term> |
-     &lt;length-multiplicative-expression> S* '/' S* &lt;length-term> |
-     &lt;length-multiplicative-expression> S+ 'mod' S+ &lt;length-term>
-
-  &lt;number-term> := '(' *S &lt;number-additive-expression> *S ')' | &lt;number>
-
-  &lt;atomic-length> := &lt;number>&lt;length-unit>
-</pre>
-
-<div class="note">Note that 'mod' is used instead of '%' for modulus since it is very easy to
-get confused about whether '%' is acting as a unit or an operator. At
-least with 'mod' it always causes a parse error &mdash; invalid unit &mdash; in the
-otherwise ambiguous cases.
-</div>
--->
-
 
 <h3>&lt;string&gt;</h3>