fix: change prefix to val__; check no atom starts with it

We now check if the prefix 'val' is in the atom name. This is because after the compilation there might be conflicts in the val predicate names.

Consider the following example: '"p a b" & val-p-a-b'

The formula is compiled as follows:

"p a b" ->  'val-p-a-b'

(:derived (val-p-a-b)        (p a b))
	      ^                  ^
	      derived-predicate  condition (ground fluent, predicate name 'p', constants 'a' and 'b')

"val-p-a-b" -> 'val-val-p-a-b'

(:derived (val-val-p-a-b)     (val-p-a-b))
	      ^                   ^
	      derived-predicate   condition (ground fluent, predicate name 'p-a-b', no constants

The prefix is changed to `val__` to make the prefix less probable to occur in an atom name.

plan4past/helpers/utils.py

@@ -29,11 +29,12 @@
 _GROUND_FLUENT_REGEX = re.compile(
     rf"(\"({_PDDL_NAME_REGEX})( {_PDDL_NAME_REGEX})*\")|({_PDDL_NAME_REGEX})"
 )
+_VAL_PREFIX = "val__"
 
 
 def add_val_prefix(name: str):
     """Add the 'prime' prefix."""
-    return "val-" + name.replace('"', "")
+    return _VAL_PREFIX + name.replace('"', "")
 
 
 def remove_before_prefix(name: str):
@@ -49,7 +50,7 @@ def remove_before_prefix(name: str):
 
 def remove_val_prefix(name: str):
     """Remove the 'prime' prefix."""
-    return name.replace("val-", "") if name.startswith("val-") else name
+    return name.replace(_VAL_PREFIX, "") if name.startswith(_VAL_PREFIX) else name
 
 
 def replace_symbols(name: str):
@@ -104,5 +105,11 @@ def validate(symbol: str) -> None:
 
     :param symbol: the symbol
     """
+    # check if the symbol does not start with the 'val__' prefix
+    if symbol.startswith(_VAL_PREFIX):
+        raise ValueError(
+            f"invalid symbol: symbol '{symbol}' cannot start with {_VAL_PREFIX}"
+        )
+
     # check if the symbol is a valid PDDL ground fluent
     parse_ground_fluent(symbol)

tests/test_helpers/test_utils.py

@@ -33,10 +33,10 @@
 
 def test_val_prefix() -> None:
     """Test the add_val_prefix function."""
-    assert add_val_prefix("Y-foo") == "val-Y-foo"
-    assert add_val_prefix("Yfoo") == "val-Yfoo"
-    assert add_val_prefix("foo") == "val-foo"
-    assert add_val_prefix("Y-foo-bar") == "val-Y-foo-bar"
+    assert add_val_prefix("Y-foo") == "val__Y-foo"
+    assert add_val_prefix("Yfoo") == "val__Yfoo"
+    assert add_val_prefix("foo") == "val__foo"
+    assert add_val_prefix("Y-foo-bar") == "val__Y-foo-bar"
 
 
 def test_remove_before_prefix() -> None:
@@ -48,7 +48,7 @@ def test_remove_before_prefix() -> None:
 
 def test_remove_val_prefix() -> None:
     """Test the remove_val_prefix function."""
-    assert remove_val_prefix("val-foo") == "foo"
+    assert remove_val_prefix("val__foo") == "foo"
     assert remove_val_prefix("foo") == "foo"