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"""Latex filters.
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Module of useful filters for processing Latex within Jinja latex templates.
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"""
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#-----------------------------------------------------------------------------
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# Copyright (c) 2013, the IPython Development Team.
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#
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# Distributed under the terms of the Modified BSD License.
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#
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# The full license is in the file COPYING.txt, distributed with this software.
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#-----------------------------------------------------------------------------
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#-----------------------------------------------------------------------------
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# Imports
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#-----------------------------------------------------------------------------
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import re
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#-----------------------------------------------------------------------------
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# Globals and constants
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#-----------------------------------------------------------------------------
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#Latex substitutions for escaping latex.
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LATEX_SUBS = (
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(re.compile('\033\[[0-9;]+m'),''), # handle console escapes
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(re.compile(r'\\'), r'\\textbackslash'),
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(re.compile(r'([{}_#%&$])'), r'\\\1'),
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(re.compile(r'~'), r'\~{}'),
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(re.compile(r'\^'), r'\^{}'),
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(re.compile(r'"'), r"''"),
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(re.compile(r'\.\.\.+'), r'\\ldots'),
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)
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#-----------------------------------------------------------------------------
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# Functions
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#-----------------------------------------------------------------------------
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__all__ = [
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'escape_latex',
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'strip_math_space'
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]
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def escape_latex(text):
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"""
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Escape characters that may conflict with latex.
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Parameters
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----------
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text : str
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Text containing characters that may conflict with Latex
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"""
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return_text = text
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for pattern, replacement in LATEX_SUBS:
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return_text = pattern.sub(replacement, return_text)
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return return_text
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def strip_math_space(text):
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"""
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Remove the space between latex math commands and enclosing $ symbols.
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This filter is important because latex isn't as flexible as the notebook
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front end when it comes to flagging math using ampersand symbols.
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Parameters
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----------
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text : str
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Text to filter.
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"""
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# First, scan through the markdown looking for $. If
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# a $ symbol is found, without a preceding \, assume
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# it is the start of a math block. UNLESS that $ is
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# not followed by another within two math_lines.
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math_regions = []
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math_lines = 0
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within_math = False
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math_start_index = 0
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ptext = ''
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last_character = ""
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skip = False
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for index, char in enumerate(text):
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#Make sure the character isn't preceeded by a backslash
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if (char == "$" and last_character != "\\"):
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# Close the math region if this is an ending $
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if within_math:
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within_math = False
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skip = True
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ptext = ptext+'$'+text[math_start_index+1:index].strip()+'$'
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math_regions.append([math_start_index, index+1])
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else:
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# Start a new math region
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within_math = True
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math_start_index = index
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math_lines = 0
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# If we are in a math region, count the number of lines parsed.
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# Cancel the math region if we find two line breaks!
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elif char == "\n":
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if within_math:
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math_lines += 1
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if math_lines > 1:
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within_math = False
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ptext = ptext+text[math_start_index:index]
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# Remember the last character so we can easily watch
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# for backslashes
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last_character = char
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if not within_math and not skip:
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ptext = ptext+char
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if skip:
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skip = False
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return ptext
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