worjk latex completion and back

IPython/core/completer.py

@@ -61,11 +61,13 b' import keyword'
 import os
 import re
 import sys
+import unicodedata
+import string
 
-from IPython.config.configurable import Configurable
+from IPython.config.configurable import Configurable 
 from IPython.core.error import TryNext
 from IPython.core.inputsplitter import ESC_MAGIC
-from IPython.core.latex_symbols import latex_symbols
+from IPython.core.latex_symbols import latex_symbols, reverse_latex_symbol
 from IPython.utils import generics
 from IPython.utils import io
 from IPython.utils.decorators import undoc
@@ -955,6 +957,88 b' class IPCompleter(Completer):'
         
         return [leading + k + suf for k in matches]
 
+    def unicode_name_matches(self, text):
+        u"""Match Latex-like syntax for unicode characters base 
+        on the name of the character.
+        
+        This does  \\GREEK SMALL LETTER ETA -> η
+
+        Works only on valid python 3 identifier, or on combining characters that 
+        will combine to form a valid identifier.
+        
+        Used on Python 3 only.
+        """
+        slashpos = text.rfind('\\')
+        if slashpos > -1:
+            s = text[slashpos+1:]
+            try :
+                unic = unicodedata.lookup(s)
+                # allow combining chars
+                if ('a'+unic).isidentifier():
+                    return '\\'+s,[unic]
+            except KeyError as e:
+                pass
+        return u'', []
+
+    def back_unicode_name_matches(self, text):
+        u"""Match unicode characters back to unicode name
+        
+        This does  ☃ -> \\snowman
+
+        Note that snowman is not a valid python3 combining character but will be expanded.
+        Though it will not recombine back to the snowman character by the completion machinery.
+
+        This will not either back-complete standard sequences like \n, \b ...
+        
+        Used on Python 3 only.
+        """
+        if len(text)<2:
+            return u'', ()
+        maybe_slash = text[-2]
+        if maybe_slash != '\\':
+            return u'', ()
+
+        char = text[-1]
+        # no expand on quote for completion in strings.
+        # nor backcomplete standard ascii keys
+        if char in string.ascii_letters or char in ['"',"'"]:
+            return u'', ()
+        try :
+            unic = unicodedata.name(char)
+            return '\\'+char,['\\'+unic]
+        except KeyError as e:
+            pass
+        return u'', ()
+
+    def back_latex_name_matches(self, text):
+        u"""Match latex characters back to unicode name
+        
+        This does  ->\\sqrt
+
+        Used on Python 3 only.
+        """
+        if len(text)<2:
+            return u'', ()
+        maybe_slash = text[-2]
+        if maybe_slash != '\\':
+            return u'', ()
+
+
+        char = text[-1]
+        # no expand on quote for completion in strings.
+        # nor backcomplete standard ascii keys
+        if char in string.ascii_letters or char in ['"',"'"]:
+            return u'', ()
+        try :
+            latex = reverse_latex_symbol[char]
+            # '\\' replace the \ as well
+            return '\\'+char,[latex]
+        except KeyError as e:
+            pass
+        return u'', ()
+
+
+
     def latex_matches(self, text):
         u"""Match Latex syntax for unicode characters.
         
@@ -1057,11 +1141,21 b' class IPCompleter(Completer):'
             cursor_pos = len(line_buffer) if text is None else len(text)
 
         if PY3:
-            latex_text = text if not line_buffer else line_buffer[:cursor_pos]
-            latex_text, latex_matches = self.latex_matches(latex_text)
-            if latex_matches:
-                return latex_text, latex_matches
 
+            base_text = text if not line_buffer else line_buffer[:cursor_pos]
+            latex_text, latex_matches = self.latex_matches(base_text)
+            if latex_matches:
+                 return latex_text, latex_matches
+            name_text = ''
+            name_matches = []
+            for meth in (self.unicode_name_matches, self.back_unicode_name_matches, self.back_latex_name_matches):
+                _name_text, _name_matches = meth(base_text)
+                if _name_text:
+                    name_text = _name_text
+                    name_matches.extend(_name_matches)
+            if name_text:
+                return name_text, name_matches
+        
         # if text is either None or an empty string, rely on the line buffer
         if not text:
             text = self.splitter.split_line(line_buffer, cursor_pos)
@@ -1170,3 +1264,4 b' class IPCompleter(Completer):'
             return self.matches[state]
         except IndexError:
             return None
+

IPython/core/latex_symbols.py

@@ -1295,3 +1295,6 b' latex_symbols = {'
     "\\mtteight" : "𝟾",
     "\\mttnine" : "𝟿",
 }
+
+
+reverse_latex_symbol = { v:k for k,v in latex_symbols.items()}

tools/gen_latex_symbols.py

@@ -76,6 +76,11 b' for line in valid_idents:'
     s += '    "%s" : "%s",\n' % (line[0], line[1])
 s += "}\n"
 
+s += """
+
+reverse_latex_symbol = { v:k for k,v in latex_symbols.items()}
+"""
+
 fn = os.path.join('..','IPython','core','latex_symbols.py')
 print("Writing the file: %s" % fn)
 with open(fn, 'w', encoding='utf-8') as f: