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| import os | |
| import logging | |
| import re | |
| from sympy.external import import_module | |
| from sympy.parsing.latex.lark.transformer import TransformToSymPyExpr | |
| _lark = import_module("lark") | |
| class LarkLaTeXParser: | |
| r"""Class for converting input `\mathrm{\LaTeX}` strings into SymPy Expressions. | |
| It holds all the necessary internal data for doing so, and exposes hooks for | |
| customizing its behavior. | |
| Parameters | |
| ========== | |
| print_debug_output : bool, optional | |
| If set to ``True``, prints debug output to the logger. Defaults to ``False``. | |
| transform : bool, optional | |
| If set to ``True``, the class runs the Transformer class on the parse tree | |
| generated by running ``Lark.parse`` on the input string. Defaults to ``True``. | |
| Setting it to ``False`` can help with debugging the `\mathrm{\LaTeX}` grammar. | |
| grammar_file : str, optional | |
| The path to the grammar file that the parser should use. If set to ``None``, | |
| it uses the default grammar, which is in ``grammar/latex.lark``, relative to | |
| the ``sympy/parsing/latex/lark/`` directory. | |
| transformer : str, optional | |
| The name of the Transformer class to use. If set to ``None``, it uses the | |
| default transformer class, which is :py:func:`TransformToSymPyExpr`. | |
| """ | |
| def __init__(self, print_debug_output=False, transform=True, grammar_file=None, transformer=None): | |
| grammar_dir_path = os.path.join(os.path.dirname(__file__), "grammar/") | |
| if grammar_file is None: | |
| with open(os.path.join(grammar_dir_path, "latex.lark"), encoding="utf-8") as f: | |
| latex_grammar = f.read() | |
| else: | |
| with open(grammar_file, encoding="utf-8") as f: | |
| latex_grammar = f.read() | |
| self.parser = _lark.Lark( | |
| latex_grammar, | |
| source_path=grammar_dir_path, | |
| parser="earley", | |
| start="latex_string", | |
| lexer="auto", | |
| ambiguity="explicit", | |
| propagate_positions=False, | |
| maybe_placeholders=False, | |
| keep_all_tokens=True) | |
| self.print_debug_output = print_debug_output | |
| self.transform_expr = transform | |
| if transformer is None: | |
| self.transformer = TransformToSymPyExpr() | |
| else: | |
| self.transformer = transformer() | |
| def doparse(self, s: str): | |
| if self.print_debug_output: | |
| _lark.logger.setLevel(logging.DEBUG) | |
| parse_tree = self.parser.parse(s) | |
| if not self.transform_expr: | |
| # exit early and return the parse tree | |
| _lark.logger.debug("expression = %s", s) | |
| _lark.logger.debug(parse_tree) | |
| _lark.logger.debug(parse_tree.pretty()) | |
| return parse_tree | |
| if self.print_debug_output: | |
| # print this stuff before attempting to run the transformer | |
| _lark.logger.debug("expression = %s", s) | |
| # print the `parse_tree` variable | |
| _lark.logger.debug(parse_tree.pretty()) | |
| sympy_expression = self.transformer.transform(parse_tree) | |
| if self.print_debug_output: | |
| _lark.logger.debug("SymPy expression = %s", sympy_expression) | |
| return sympy_expression | |
| if _lark is not None: | |
| _lark_latex_parser = LarkLaTeXParser() | |
| def parse_latex_lark(s: str): | |
| """ | |
| Experimental LaTeX parser using Lark. | |
| This function is still under development and its API may change with the | |
| next releases of SymPy. | |
| """ | |
| if _lark is None: | |
| raise ImportError("Lark is probably not installed") | |
| return _lark_latex_parser.doparse(s) | |
| def _pretty_print_lark_trees(tree, indent=0, show_expr=True): | |
| if isinstance(tree, _lark.Token): | |
| return tree.value | |
| data = str(tree.data) | |
| is_expr = data.startswith("expression") | |
| if is_expr: | |
| data = re.sub(r"^expression", "E", data) | |
| is_ambig = (data == "_ambig") | |
| if is_ambig: | |
| new_indent = indent + 2 | |
| else: | |
| new_indent = indent | |
| output = "" | |
| show_node = not is_expr or show_expr | |
| if show_node: | |
| output += str(data) + "(" | |
| if is_ambig: | |
| output += "\n" + "\n".join([" " * new_indent + _pretty_print_lark_trees(i, new_indent, show_expr) for i in tree.children]) | |
| else: | |
| output += ",".join([_pretty_print_lark_trees(i, new_indent, show_expr) for i in tree.children]) | |
| if show_node: | |
| output += ")" | |
| return output | |