w3c
diff --git a/‎css3-values/Overview.src.html‎
Lines changed: 61 additions & 17 deletions b/‎css3-values/Overview.src.html‎
Lines changed: 61 additions & 17 deletions
@@ -475,14 +475,10 @@ <h5>The 'vm' unit</h5>
 units. When the height or width of the viewport is changed, lengths
 specified in the 'vm' unit are scaled proportionally.
 
-<h4>The 'calc' function</h4>
+<h4>The 'calc', 'min' and 'max' functions</h4>
 
-<p>The <dfn>calc(&lt;expression&gt;)</dfn> function can be used wherever length values are allowed, with the syntax given below.
+<p>The <dfn>calc()</dfn>, <dfn>min()</dfn>, and <dfn>max()</dfn> functions can be used wherever length values are allowed. 
 
-<!--
-The expression within the parethesis is computed at the same time as 'em' lengths are
-computed
--->
 
 <div class="example">
 <pre>
@@ -498,16 +494,64 @@ <h4>The 'calc' function</h4>
 <pre>
 p {
   margin: calc(1rem - 2px) calc(1rem - 1px);
-  border: solid transparent; border-width: 2px 1px;
 }
 </pre>
 </div>
 
+<div class="example">
+<pre>
+p { font-size: min(10px, 3em) }
+blockquote { font-size: max(30px, 3em) }
+</pre>
+</div>
+
+<div class="example">
+<pre>
+.box { width: min(10% + 20px, 300px) }
+</pre>
+</div>
 
-<p>The simple expression language of the 'calc()' function supports
-five arithmetic operators (+ and - have lowest precedence, *, /, and
-'mod' have highest precedence) and parentheses.
 
+<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 [ [ "*" | "/" | "mod" ] S* unit ]*;
+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,
+angle, time, or number. Any PERCENTAGE token in the expression also
+has that type. The NUMBER tokens obviously are of type number, and the
+DIMENSION tokens have types that depend on their units (cm, px, deg,
+etc.). At each operator, the types of the left and right side have to
+be compared and, if compatible, they yield a result type, roughly as
+follows (the following ignores precedence rules on the operators for
+simplicity):
+
+<ol>
+<li>At ",", "+", "-":<br>
+   check: both sides have the same type<br>
+   return: that type
+<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"
+</ol>
+
+
+<!--
 <p>A value is ignored if a division by zero or other mathematical
  errors occur in the calculation.
 
@@ -522,7 +566,6 @@ <h4>The 'calc' function</h4>
 </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.
 
 
@@ -531,7 +574,7 @@ <h4>The 'calc' function</h4>
 <pre>
   &lt;length> := calc( &lt;length-expression> ) | &lt;atomic-length>
 
-  &lt;length-expression> := &lt;length-additive-expression>
+  &lt;length-expression> := S* &lt;length-additive-expression> S*
 
   &lt;length-additive-expression> :=
      &lt;length-multiplicative-expression> |
@@ -557,7 +600,7 @@ <h4>The 'calc' function</h4>
      &lt;length-multiplicative-expression> S* '/' S* &lt;length-term> |
      &lt;length-multiplicative-expression> S+ 'mod' S+ &lt;length-term>
 
-  &lt;number-term> := '(' &lt;number-additive-expression> ')' | &lt;number>
+  &lt;number-term> := '(' *S &lt;number-additive-expression> *S ')' | &lt;number>
 
   &lt;atomic-length> := &lt;number>&lt;length-unit>
 </pre>
@@ -567,6 +610,7 @@ <h4>The 'calc' function</h4>
 least with 'mod' it always causes a parse error &mdash; invalid unit &mdash; in the
 otherwise ambiguous cases.
 </div>
+-->
 
 
 <h3>&lt;string&gt;</h3>
@@ -1086,13 +1130,13 @@ <h4>Font families</h4>
 <h2>Specified, computed, used, and actual values</h2>
 
 <p>The final value of a CSS3 property for a given element is the
-result of a three-step calculation. First, cascading and inheritance
+result of a four-step calculation. First, cascading and inheritance
 yields the <em>specified value</em> [[!CSS3CASCADE]]. Second, relative
 values are computed into absolute values as far as possible without
 formatting the document, thereby yielding the <em>computed value</em>.
-Finally, the computed value is transformed to the <em>actual
-value</em> in the layout process.</p>
-
+The computed value is tranformed into the <em>used value</em> in the
+formatting process. Finally, the computed value is transformed to
+the <em>actual value</em> based on constraints in the user agent.</p>
 
 <h3>Finding the <dfn>specified value</dfn></h3>