tweaked docs

doc/filters/filter.rst

@@ -11,11 +11,22 @@ function. The arrow function receives the value of the sequence or mapping:
 
     {% set sizes = [34, 36, 38, 40, 42] %}
 
+    {{ sizes|filter(v => v > 38)|join(', ') }}
+    {# output 40, 42 #}
+
+Combined with the ``for`` tag, it allows to filter the itemss to iterate over:
+
+.. code-block:: twig
+
     {% for v in sizes|filter(v => v > 38) -%}
         {{ v }}
     {% endfor %}
     {# output 40 42 #}
 
+It also works with mappings:
+
+.. code-block:: twig
+
     {% set sizes = {
         xs: 34,
         s:  36,
@@ -29,9 +40,6 @@ function. The arrow function receives the value of the sequence or mapping:
     {% endfor %}
     {# output l = 40 xl = 42 #}
 
-    {{ sizes|filter(v => v > 38)|join(', ') }}
-    {# output 40, 42 #}
-
 The arrow function also receives the key as a second argument:
 
 .. code-block:: twig