Add keepdot and filtdot operators

docs/sardine_doc/src/pattern_languages/sardine/filter_functions.md

@@ -2,7 +2,7 @@
 
 There is a group of functions used for filtering: removing events, filtering values, etc... These functions are very low-level but they can be really interesting for specific use cases.
 
-## mask 
+## mask
 
 
 Apply a boolean mask on values from the collection. True values will return the value itself, others will return a silence. This function is used by others for many different operations.
@@ -43,3 +43,33 @@ This function can be used to filter some values from a pattern. Imagine generati
 # Removing 2 and 4 from the generated ramp
 Pa * d('hat', p=.25, speed='(filter [0:10] [2 4])')
 ```
+
+
+## filtdot
+
+This function can be used to filter out some values from a pattern, replacing them with silences (.).
+
+**Arguments:**
+- **collection:** the collection you would like to filter.
+- **filter:** a list containing the elements to filter
+
+**Example:**
+```python
+# Replacing 2 and 4 By silences
+Pa * d('hat', p=.25, speed='(filtdot [0:10] [2 4])')  # Equivalent to speed='0 1 . 3 . 5 6 7 8 9 10'
+```
+
+
+## keepdot
+
+This function does the opposite of filtdot: only the values that are in the given filter are kept.
+
+**Arguments:**
+- **collection:** the collection you would like to filter.
+- **filter:** a list containing the elements to keep
+
+**Example:**
+```python
+# Replacing 2 and 4 By silences
+Pa * d('hat', p=.25, speed='(keepdot [0:10] [2 4])')  # Equivalent to speed='. . 2 . 4 . . . . . .'
+```

sardine_core/sequences/sardine_parser/funclib.py

@@ -505,6 +505,12 @@ def notdot(self, collection: list) -> list:
         """Invert a rhythm pattern (1 -> ., . -> 1)"""
         return [1 if x == None else None for x in collection]
 
+    def filtdot(self, collection: list, filter_: list) -> list:
+        return [x if x not in filter_ else None for x in collection]
+
+    def keepdot(self, collection: list, keep_: list) -> list:
+        return [x if x in keep_ else None for x in collection]
+
     def clamp(
         self,
         collection: list,

sardine_core/sequences/sardine_parser/tree_calc.py

@@ -571,6 +571,8 @@ def function_call(self, func_name, *args):
                 "neu": self.library.negative_euclidian_rhythm,
                 "mask": self.library.mask,
                 "notdot": self.library.notdot,
+                "filtdot": self.library.filtdot,
+                "keepdot": self.library.keepdot,
                 "euclid": self.library.euclidian_to_number,
                 "numclid": self.library.euclidian_to_number,
                 "e": self.library.euclidian_to_number,