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""" |
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A few practical conventions common to all printers. |
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""" |
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import re |
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from collections.abc import Iterable |
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from sympy.core.function import Derivative |
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_name_with_digits_p = re.compile(r'^([^\W\d_]+)(\d+)$', re.UNICODE) |
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def split_super_sub(text): |
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"""Split a symbol name into a name, superscripts and subscripts |
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The first part of the symbol name is considered to be its actual |
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'name', followed by super- and subscripts. Each superscript is |
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preceded with a "^" character or by "__". Each subscript is preceded |
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by a "_" character. The three return values are the actual name, a |
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list with superscripts and a list with subscripts. |
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Examples |
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======== |
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>>> from sympy.printing.conventions import split_super_sub |
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>>> split_super_sub('a_x^1') |
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('a', ['1'], ['x']) |
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>>> split_super_sub('var_sub1__sup_sub2') |
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('var', ['sup'], ['sub1', 'sub2']) |
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""" |
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if not text: |
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return text, [], [] |
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pos = 0 |
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name = None |
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supers = [] |
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subs = [] |
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while pos < len(text): |
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start = pos + 1 |
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if text[pos:pos + 2] == "__": |
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start += 1 |
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pos_hat = text.find("^", start) |
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if pos_hat < 0: |
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pos_hat = len(text) |
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pos_usc = text.find("_", start) |
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if pos_usc < 0: |
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pos_usc = len(text) |
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pos_next = min(pos_hat, pos_usc) |
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part = text[pos:pos_next] |
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pos = pos_next |
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if name is None: |
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name = part |
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elif part.startswith("^"): |
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supers.append(part[1:]) |
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elif part.startswith("__"): |
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supers.append(part[2:]) |
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elif part.startswith("_"): |
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subs.append(part[1:]) |
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else: |
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raise RuntimeError("This should never happen.") |
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m = _name_with_digits_p.match(name) |
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if m: |
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name, sub = m.groups() |
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subs.insert(0, sub) |
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return name, supers, subs |
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def requires_partial(expr): |
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"""Return whether a partial derivative symbol is required for printing |
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This requires checking how many free variables there are, |
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filtering out the ones that are integers. Some expressions do not have |
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free variables. In that case, check its variable list explicitly to |
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get the context of the expression. |
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""" |
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if isinstance(expr, Derivative): |
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return requires_partial(expr.expr) |
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if not isinstance(expr.free_symbols, Iterable): |
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return len(set(expr.variables)) > 1 |
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return sum(not s.is_integer for s in expr.free_symbols) > 1 |
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