Merge branch 'u/dlucas/abstract_lin_code_print_error_messages' of tra…

…c.sagemath.org:sage into abstract_lin_code_print_error_messages

src/sage/coding/linear_code.py

@@ -588,20 +588,97 @@ def __init__(self, base_field, length, default_encoder_name, default_decoder_nam
         self.Element = type(facade_for.an_element()) #for when we made this a non-facade parent
         Parent.__init__(self, base=base_field, facade=facade_for, category=cat)
 
-    def _latex_(self):
+    def _repr_(self):
+        r"""
+        Returns an error message requiring to override ``_repr_`` in ``self``.
+
+        As one has to implement specific representation methods (`_repr_` and `_latex_`)
+        when writing a new code class which inherits from :class:`AbstractLinearCode`,
+        the generic call to `_repr_` has to fail.
+
+        EXAMPLES:
+
+        This was taken from :trac:20899 (and thus ensures this method fixes what was
+        described in this ticket).
+
+        We create a new code class, its dedicated encoder
+        and set appropriate parameters::
+
+        sage: from sage.coding.linear_code import AbstractLinearCode
+        sage: from sage.coding.encoder import Encoder
+        sage: class MyCode(AbstractLinearCode):
+        ....:    _registered_encoders = {}
+        ....:    _registered_decoders = {}
+        ....:    def __init__(self):
+        ....:        super(MyCode, self).__init__(GF(5), 10, "Monkey", "Syndrome")
+        ....:        self._dimension = 2
+
+        sage: class MonkeyEncoder(Encoder):
+        ....:    def __init__(self, C):
+        ....:        super(MonkeyEncoder, self).__init__(C)
+        ....:    @cached_method
+        ....:    def generator_matrix(self):
+        ....:        return matrix(GF(5), 2, 10, [ [1]*5 + [0]*5, [0]*5 + [1]*5 ])
+        sage: MyCode._registered_encoders["Monkey"] = MonkeyEncoder
+        sage: MyCode._registered_decoders["Syndrome"] = codes.decoders.LinearCodeSyndromeDecoder
+
+        We check we get a sensible error message while asking for a string
+        representation of an instance of our new class:
+
+        sage: C = MyCode()
+        sage: C #random
+        Traceback (most recent call last):
+        ...
+        RuntimeError: Please override _repr_ in the implementation of <class '__main__.MyCode_with_category'>
         """
-        Return a latex representation of ``self``.
+        raise RuntimeError("Please override _repr_ in the implementation of %s"
+                 % self.parent())
 
-        EXAMPLES::
+    def _latex_(self):
+        r"""
+        Returns an error message requiring to override ``_latex_`` in ``self``.
 
-            sage: MS = MatrixSpace(GF(2),4,7)
-            sage: G  = MS([[1,1,1,0,0,0,0], [1,0,0,1,1,0,0], [0,1,0,1,0,1,0], [1,1,0,1,0,0,1]])
-            sage: C  = LinearCode(G)
-            sage: latex(C)
-            [7, 4]\textnormal{ Linear code over }\Bold{F}_{2}
+        As one has to implement specific representation methods (`_repr_` and `_latex_`)
+        when writing a new code class which inherits from :class:`AbstractLinearCode`,
+        the generic call to `_latex_` has to fail.
+
+        EXAMPLES:
+
+        This was taken from :trac:20899 (and thus ensures this method fixes what was
+        described in this ticket).
+
+        We create a new code class, its dedicated encoder
+        and set appropriate parameters::
+
+        sage: from sage.coding.linear_code import AbstractLinearCode
+        sage: from sage.coding.encoder import Encoder
+        sage: class MyCode(AbstractLinearCode):
+        ....:    _registered_encoders = {}
+        ....:    _registered_decoders = {}
+        ....:    def __init__(self):
+        ....:        super(MyCode, self).__init__(GF(5), 10, "Monkey", "Syndrome")
+        ....:        self._dimension = 2
+
+        sage: class MonkeyEncoder(Encoder):
+        ....:    def __init__(self, C):
+        ....:        super(MonkeyEncoder, self).__init__(C)
+        ....:    @cached_method
+        ....:    def generator_matrix(self):
+        ....:        return matrix(GF(5), 2, 10, [ [1]*5 + [0]*5, [0]*5 + [1]*5 ])
+        sage: MyCode._registered_encoders["Monkey"] = MonkeyEncoder
+        sage: MyCode._registered_decoders["Syndrome"] = codes.decoders.LinearCodeSyndromeDecoder
+
+        We check we get a sensible error message while asking for a string
+        representation of an instance of our new class:
+
+        sage: C = MyCode()
+        sage: latex(C)
+        Traceback (most recent call last):
+        ...
+        RuntimeError: Please override _latex_ in the implementation of <class '__main__.MyCode_with_category'>
         """
-        return "[%s, %s]\\textnormal{ Linear code over }%s"\
-                % (self.length(), self.dimension(), self.base_ring()._latex_())
+        raise RuntimeError("Please override _latex_ in the implementation of %s"
+                 % self.parent())
 
     def _an_element_(self):
         r"""
@@ -3703,6 +3780,21 @@ def _repr_(self):
         else:
             return "[%s, %s] linear code over %s"%(self.length(), self.dimension(), R)
 
+    def _latex_(self):
+        """
+        Return a latex representation of ``self``.
+
+        EXAMPLES::
+
+            sage: MS = MatrixSpace(GF(2),4,7)
+            sage: G  = MS([[1,1,1,0,0,0,0], [1,0,0,1,1,0,0], [0,1,0,1,0,1,0], [1,1,0,1,0,0,1]])
+            sage: C  = LinearCode(G)
+            sage: latex(C)
+            [7, 4]\textnormal{ Linear code over }\Bold{F}_{2}
+        """
+        return "[%s, %s]\\textnormal{ Linear code over }%s"\
+                % (self.length(), self.dimension(), self.base_ring()._latex_())
+
     def __hash__(self):
         r"""
         Returns the hash value of ``self``.