Adds an ordset update function.

1 files changed, 30 insertions, 0 deletions

diff --git a/src/ataxic_sugar.erl b/src/ataxic_sugar.erl
index 556e08a..eb0ef57 100644
--- a/src/ataxic_sugar.erl
+++ b/src/ataxic_sugar.erl
@@ -12,6 +12,7 @@
    [
       update_array_cell/2,
       update_orddict_element/2,
+      update_ordset/2,
       nop/0
    ]
 ).
@@ -84,3 +85,32 @@ update_orddict_element (IX, OP) ->
 
 -spec nop () -> ataxic:basic().
 nop () -> ataxic:sequence([]).
+
+-spec update_ordset (ordsets:ordset(), ordsets:ordeset()) -> ataxic:basic().
+update_ordset (Old, New) ->
+   Remove = ordsets:substract(Old, New),
+   Add = ordsets:substract(New, Old),
+
+   ataxic:sequence
+   (
+      [
+         ataxic:apply_function
+         (
+            ordsets,
+            substract,
+            [
+               ataxic:current_value(),
+               ataxic:constant(Remove)
+            ]
+         ),
+         ataxic:apply_function
+         (
+            ordsets,
+            union,
+            [
+               ataxic:current_value(),
+               ataxic:constant(Add)
+            ]
+         )
+      ]
+   ).