From 328a2ce9c1ec94db971915a6d1b949084e16667a 2013-02-21 18:15:26
From: Jonathan Frederic <jdfreder@calpoly.edu>
Date: 2013-02-21 18:15:26
Subject: [PATCH] Added code to fix the math $ in the notebook so it
works with markdown2latex.

---

diff --git a/converters/latex_transformer.py b/converters/latex_transformer.py
new file mode 100644
index 0000000..7e52e7e
--- /dev/null
+++ b/converters/latex_transformer.py
@@ -0,0 +1,139 @@
+"""
+Module that allows latex output notebooks to be conditioned before 
+they are converted.
+"""
+
+# Configurable traitlets
+from IPython.utils.traitlets import Unicode, Bool
+
+# Needed to override transformer
+from converters.transformers import (ActivatableTransformer)
+
+class LatexTransformer(ActivatableTransformer):
+    """
+    Converter for latex destined documents.
+    """    
+    
+    def __call__(self, nb, other):
+        """
+        Entrypoint
+        
+        nb - Input notebook
+        other - Maps to 'resources' in Jinja
+        """
+        
+        # Only run if enabled.
+        if self.enabled:
+            return self.Transform(nb, other)
+            
+    def Transform(self, nb, other):
+        """
+        Transform the notebook to make it compatible with markdown2latex.
+        """
+        
+        #Fix the markdown in every markdown cell.
+        for sheet in nb.worksheets:
+            for cell in sheet.cells:
+                if hasattr(cell, "source") and cell.cell_type == "markdown":
+                    cell.source = self.remove_math_space(cell.source)
+        return nb, other
+    
+    def remove_math_space(self, 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
+        index = 0
+        last_character = ""
+        for char in text: #Loop through each character in the 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
+                    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
+                        
+            # Remember the last character so we can easily watch
+            # for backslashes
+            last_character = char
+            
+            # Next index
+            index += 1
+        
+        # Reset the index and last char
+        index = 0
+        
+        # Now that we know what regions of the text are math and
+        # what regions aren't, we can separate them into "blocks"
+        text_blocks=[]
+        math_blocks=[]
+        was_math_block = False
+        current_block = ""
+        for char in text:
+            
+            # Check if this is a math region.
+            ismath = False
+            for keypair in math_regions:
+                if (keypair[0] <= index and index <=  keypair[1]):
+                    ismath = True
+            
+            # If the region type has changed since the last
+            # iteration, commit all read characters to that
+            # region type and reset the buffer.
+            if (ismath and not was_math_block):
+                was_math_block = True
+                text_blocks.append(current_block)
+                current_block=""
+            elif ((not ismath) and was_math_block):
+                was_math_block = False
+                math_blocks.append(current_block)
+                current_block=""
+            
+            # Store the character
+            current_block += char
+            
+            # Next index
+            index += 1
+            
+        # Save whatever remains in the buffer that hasn't yet been saved.
+        if was_math_block:
+            math_blocks.append(current_block)
+        else:
+            text_blocks.append(current_block)
+            
+        # Recombine the regions, while processing every math region, removing
+        # the spaces between the math and the $ symbols.
+        output = ""
+        for index in range(0,len(text_blocks) + len(math_blocks)):
+            if index % 2 == 0:
+                output += text_blocks[index/2]
+            else:
+                mathblock = math_blocks[(index -1)/2]
+                mathblock = mathblock[1:len(mathblock)-2]
+                output += "$" + mathblock.strip() + "$"
+        return output
+        
\ No newline at end of file
diff --git a/converters/template.py b/converters/template.py
index 7616bc7..bbe8e34 100755
--- a/converters/template.py
+++ b/converters/template.py
@@ -37,6 +37,7 @@ from jinja2 import Environment, FileSystemLoader
 # local import (pre-transformers)
 import converters.transformers as trans
 from converters.sphinx_transformer import (SphinxTransformer)
+from converters.latex_transformer import (LatexTransformer)
 
 # some jinja filters
 from converters.jinja_filters import (python_comment, indent,
diff --git a/profile/latex_base.nbcv b/profile/latex_base.nbcv
index 2b4fede..450ac7a 100644
--- a/profile/latex_base.nbcv
+++ b/profile/latex_base.nbcv
@@ -13,3 +13,6 @@ c.ExtractFigureTransformer.display_data_priority=['latex', 'svg', 'png', 'jpg', 
 
 c.ExtractFigureTransformer.extra_ext_map={'svg':'pdf'}
 c.ExtractFigureTransformer.enabled=True
+
+# Enable latex transformer (make markdown2latex work with math $.)
+c.LatexTransformer.enabled=True