diff options
| -rw-r--r-- | pyparsing/core.py | 35 |
1 files changed, 29 insertions, 6 deletions
diff --git a/pyparsing/core.py b/pyparsing/core.py index 8a0f4dd..a3e2d8f 100644 --- a/pyparsing/core.py +++ b/pyparsing/core.py @@ -776,7 +776,21 @@ class ParserElement(ABC): _left_recursion_enabled = False @staticmethod - def enable_left_recursion(): + def disable_memoization(): + """ + Disables active Packrat or Left Recursion parsing and their memooization + + This method also works if neither Packrat nor Left Recursion are enabled. + This makes it safe to call before activating Packrat nor Left Recursion + to clear any previous settings. + """ + ParserElement.resetCache() + ParserElement._left_recursion_enabled = False + ParserElement._packratEnabled = False + ParserElement._parse = ParserElement._parseNoCache + + @staticmethod + def enable_left_recursion(*, force=False): """ Enables "bounded recursion" parsing, which allows for both direct and indirect left-recursion. During parsing, left-recursive :class:`Forward` elements are @@ -799,15 +813,18 @@ class ParserElement(ABC): may thus skip evaluation during backtracking. This may break existing programs with parse actions which rely on side-effects. - Bounded Recursion parsing works similar but not identical to Packrat parsing. - Thus the two cannot be used together. + Bounded Recursion parsing works similar but not identical to Packrat parsing, + thus the two cannot be used together. Use ``force=True`` to disable any + previous, conflicting settings. """ - if ParserElement._packratEnabled: + if force: + ParserElement.disable_memoization() + elif ParserElement._packratEnabled: raise RuntimeError("Packrat and Bounded Recursion are not compatible") ParserElement._left_recursion_enabled = True @staticmethod - def enablePackrat(cache_size_limit=128): + def enablePackrat(cache_size_limit=128, *, force=False): """Enables "packrat" parsing, which adds memoizing to the parsing logic. Repeated parse attempts at the same string location (which happens often in many complex grammars) can immediately return a cached value, @@ -832,8 +849,14 @@ class ParserElement(ABC): import pyparsing pyparsing.ParserElement.enablePackrat() + + Packrat parsing works similar but not identical to Bounded Recursion parsing, + thus the two cannot be used together. Use ``force=True`` to disable any + previous, conflicting settings. """ - if ParserElement._left_recursion_enabled: + if force: + ParserElement.disable_memoization() + elif ParserElement._left_recursion_enabled: raise RuntimeError("Packrat and Bounded Recursion are not compatible") if not ParserElement._packratEnabled: ParserElement._packratEnabled = True |