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from sympy.external import import_module |
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from sympy.utilities.decorator import doctest_depends_on |
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from sympy.parsing.latex.lark import LarkLaTeXParser, TransformToSymPyExpr, parse_latex_lark |
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from .errors import LaTeXParsingError |
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__doctest_requires__ = {('parse_latex',): ['antlr4', 'lark']} |
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@doctest_depends_on(modules=('antlr4', 'lark')) |
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def parse_latex(s, strict=False, backend="antlr"): |
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r"""Converts the input LaTeX string ``s`` to a SymPy ``Expr``. |
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Parameters |
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========== |
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s : str |
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The LaTeX string to parse. In Python source containing LaTeX, |
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*raw strings* (denoted with ``r"``, like this one) are preferred, |
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as LaTeX makes liberal use of the ``\`` character, which would |
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trigger escaping in normal Python strings. |
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backend : str, optional |
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Currently, there are two backends supported: ANTLR, and Lark. |
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The default setting is to use the ANTLR backend, which can be |
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changed to Lark if preferred. |
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Use ``backend="antlr"`` for the ANTLR-based parser, and |
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``backend="lark"`` for the Lark-based parser. |
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The ``backend`` option is case-sensitive, and must be in |
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all lowercase. |
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strict : bool, optional |
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This option is only available with the ANTLR backend. |
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If True, raise an exception if the string cannot be parsed as |
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valid LaTeX. If False, try to recover gracefully from common |
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mistakes. |
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Examples |
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======== |
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>>> from sympy.parsing.latex import parse_latex |
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>>> expr = parse_latex(r"\frac {1 + \sqrt {\a}} {\b}") |
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>>> expr |
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(sqrt(a) + 1)/b |
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>>> expr.evalf(4, subs=dict(a=5, b=2)) |
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1.618 |
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>>> func = parse_latex(r"\int_1^\alpha \dfrac{\mathrm{d}t}{t}", backend="lark") |
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>>> func.evalf(subs={"alpha": 2}) |
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0.693147180559945 |
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""" |
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if backend == "antlr": |
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_latex = import_module( |
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'sympy.parsing.latex._parse_latex_antlr', |
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import_kwargs={'fromlist': ['X']}) |
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if _latex is not None: |
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return _latex.parse_latex(s, strict) |
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elif backend == "lark": |
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return parse_latex_lark(s) |
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else: |
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raise NotImplementedError(f"Using the '{backend}' backend in the LaTeX" \ |
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" parser is not supported.") |
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