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