Update Language-Definition.md

Author: antonmedv

docs/Language-Definition.md

@@ -1,6 +1,22 @@
 # Language Definition
 
-**Expr** is an expression evaluation language for Go.
+<table>
+  <tr><th colspan="2">Built-in Functions</th></tr>
+  <tr>
+    <td>
+      <a href="#allarray-predicate">all()</a><br>
+      <a href="#anyarray-predicate">any()</a><br>
+      <a href="#lenarray-predicate">one()</a><br>
+      <a href="#nonearray-predicate">none()</a><br>
+    </td>
+    <td>
+      <a href="#lenv">len()</a><br>
+      <a href="#maparray-predicate">map()</a><br>
+      <a href="#filterarray-predicate">filter()</a><br>
+      <a href="#countarray-predicate">count()</a><br>    
+    </td>
+  </tr>
+</table>
 
 ## Supported Literals
 
@@ -15,7 +31,8 @@ The package supports:
 
 ## Digit separators
 
-Integer literals may contain digit separators to allow digit grouping into more legible forms.
+Integer literals may contain digit separators to allow digit grouping into more
+legible forms.
 
 Example:
 
@@ -25,7 +42,8 @@ Example:
 
 ## Fields
 
-Struct fields and map elements can be accessed by using the `.` or the `[]` syntax.
+Struct fields and map elements can be accessed by using the `.` or the `[]`
+syntax.
 
 ```js
 foo.Field
@@ -107,7 +125,7 @@ user.Group in ["human_resources", "marketing"]
 "foo" in {foo: 1, bar: 2}
 ```
 
-### Numeric Operators
+### Range Operator
 
 * `..` (range)
 
@@ -123,7 +141,24 @@ The range is inclusive:
 1..3 == [1, 2, 3]
 ```
 
-### Ternary Operators
+### Slice Operator
+
+* `array[:]` (slice)
+
+Slices can work with arrays or strings.
+
+Example:
+
+Variable `array` is `[1,2,3,4,5]`.
+
+```js
+array[1:4] == [2,3,4]
+array[:3] == [1,2,3]
+array[3:] == [4,5]
+array[:] == array
+```
+
+### Ternary Operator
 
 * `foo ? 'yes' : 'no'`
 
@@ -135,98 +170,69 @@ user.Age > 30 ? "mature" : "immature"
 
 ## Built-in Functions
 
-<table>
-<tr>
-  <td>
-    <a href="#allarray-predicate">all()</a><br>
-    <a href="#anyarray-predicate">any()</a><br>
-    <a href="#lenarray-predicate">one()</a><br>
-    <a href="#nonearray-predicate">none()</a><br>
-  </td>
-  <td>
-    <a href="#lenv">len()</a><br>
-    <a href="#maparray-closure">map()</a><br>
-    <a href="#filterarray-predicate">filter()</a><br>
-    <a href="#countarray-predicate">count()</a><br>    
-  </td>
-</tr>
-</table>
-
-
 ### `all(array, predicate)`
 
-Returns **true** if all elements satisfies the predicate (or if the array is empty).
+Returns **true** if all elements satisfies the [predicate](#predicate).
+If the array is empty, returns **true**.
 
 ```js
 all(Tweets, {.Size < 280})
 ```
 
 ### `any(array, predicate)`
 
-Returns **true** if any elements satisfies the predicate. If the array is empty, returns **false**.
+Returns **true** if any elements satisfies the [predicate](#predicate).
+If the array is empty, returns **false**.
 
 
 ### `one(array, predicate)`
 
-Returns **true** if _exactly one_ element satisfies the predicate. If the array is empty, returns **false**.
+Returns **true** if _exactly one_ element satisfies the [predicate](#predicate).
+If the array is empty, returns **false**.
 
 ```js
 one(Participants, {.Winner})
 ```
 
 ### `none(array, predicate)`
 
-Returns **true** if _all elements does not_ satisfy the predicate. If the array is empty, returns **true**.
+Returns **true** if _all elements does not_ satisfy the [predicate](#predicate).
+If the array is empty, returns **true**.
 
 ### `len(v)`
 
 Returns the length of an array, a map or a string.
 
-### `map(array, closure)`
+### `map(array, predicate)`
 
-Returns new array by applying the closure to each element of the array.
+Returns new array by applying the [predicate](#predicate) to each element of
+the array.
 
 ### `filter(array, predicate)`
 
-Returns new array by filtering elements of the array by predicate.
+Returns new array by filtering elements of the array by [predicate](#predicate).
 
 ### `count(array, predicate)`
 
-Returns the number of elements what satisfies the predicate. Equivalent to:
+Returns the number of elements what satisfies the [predicate](#predicate).
+Equivalent to:
 
 ```js
 len(filter(array, predicate))
 ```
 
-## Closures
+## Predicate
 
-The closure is an expression that accepts a single argument. To access 
+The predicate is an expression that accepts a single argument. To access 
 the argument use the `#` symbol.
 
 ```js
 map(0..9, {# / 2})
 ```
 
-If the item of array is struct, it is possible to access fields of struct with 
+If items of the array is a struct or a map, it is possible to access fields with 
 omitted `#` symbol (`#.Value` becomes `.Value`).
 
 ```js
 filter(Tweets, {len(.Value) > 280})
 ```
-
-## Slices
-
-* `array[:]` (slice)
-
-Slices can work with arrays or strings.
-
-Example:
-
-Variable `array` is `[1,2,3,4,5]`.
-
-```js
-array[1:4] == [2,3,4]
-array[:3] == [1,2,3]
-array[3:] == [4,5]
-array[:] == array
-```