transformers/latex.py

"""
Module that allows latex output notebooks to be conditioned before
they are converted.
"""
from __future__ import absolute_import

# Configurable traitlets

# Needed to override transformer
from .transformers import (ActivatableTransformer)

class LatexTransformer(ActivatableTransformer):
    """
    Converter for latex destined documents.
    """

    def cell_transform(self, cell, other, index):
        """
        Apply a transformation on each cell,

        receive the current cell, the resource dict and the index of current cell as parameter.

        Returns modified cell and resource dict.
        """
        if hasattr(cell, "source") and cell.cell_type == "markdown":
            cell.source = rm_math_space(cell.source)
        return cell, other

def rm_math_space(text):
    """
    Remove the space between latex math commands and enclosing $ symbols.
    """

    # First, scan through the markdown looking for $.  If
    # a $ symbol is found, without a preceding \, assume
    # it is the start of a math block.  UNLESS that $ is
    # not followed by another within two math_lines.
    math_regions = []
    math_lines = 0
    within_math = False
    math_start_index = 0
    ptext = ''
    last_character = ""
    skip = False
    for index, char in enumerate(text):
        #Make sure the character isn't preceeded by a backslash
        if (char == "$" and last_character != "\\"):
            # Close the math region if this is an ending $
            if within_math:
                within_math = False
                skip = True
                ptext = ptext+'$'+text[math_start_index+1:index].strip()+'$'
                math_regions.append([math_start_index, index+1])
            else:
                # Start a new math region
                within_math = True
                math_start_index = index
                math_lines = 0
        # If we are in a math region, count the number of lines parsed.
        # Cancel the math region if we find two line breaks!
        elif char == "\n":
            if within_math:
                math_lines += 1
                if math_lines > 1:
                    within_math = False
                    ptext = ptext+text[math_start_index:index]

        # Remember the last character so we can easily watch
        # for backslashes
        last_character = char
        if not within_math and not skip:
            ptext = ptext+char
        if skip:
            skip = False
    return ptext