[simplex] Add __str__ method for simplex dictionary.

simplex/simplex_dictionary.py

@@ -31,7 +31,7 @@ class simplex_dictionary(typing.Generic[V]):
       - N The list of non-basic variables (immutable).
       - b The current value of the basic variables.
       - a The current coefficients of the non-basic variables in the expression
-          of the basic variables.
+        of the basic variables.
       - c The current coefficients of the non-basic variables in the objective.
       - z The current value of the objective.
 
@@ -91,18 +91,22 @@ class simplex_dictionary(typing.Generic[V]):
 
     @property
     def variables(self) -> typing.List[V]:
+        """ Returns: The list of variables in this dictionary. """
         return sorted(self.B + self.N)
 
     @property
     def B(self) -> typing.List[V]:
+        """ Returns: The list of basic variables for this dictionary. """
         return self.__B
 
     @property
     def N(self) -> typing.List[V]:
+        """ Returns: The list of non-basic variables for this dictionary. """
         return self.__N
 
     @property
     def a(self) -> magic_dictionary[V, magic_dictionary[V, Fraction]]:
+        """ Returns: The a matrix of this dictionary. """
         return self._a
 
     @a.setter
@@ -232,3 +236,50 @@ class simplex_dictionary(typing.Generic[V]):
             d = r"{} = \left.{}\right.".format(name, d)
 
         display(Math(d))
+
+    def __str__(self) -> str:
+        # Length for the variables:
+        vnames = [str(x) for x in self.variables]
+        vlength = max(len(n) for n in vnames)
+
+        # Length for the b column:
+        z = str(self.z)
+        b = [str(self.b[x]) for x in self.B]
+        blength = max(len(z), max(len(n) for n in b))
+
+        # Length for the other columns:
+        a = [[str(self.a[xb][xn]) for xn in self.N] for xb in self.B]
+        c = [str(self.c[xn]) for xn in self.N]
+        alength = max(
+            vlength, max(len(n) for r in a for n in r), max(len(n) for n in c)
+        )
+
+        # Create the string:
+        row_format_s = " {:>{vwidth}} | {:>{bwidth}} | "
+        row_format_s += " | ".join("{:>{awidth}}" for _ in self.N)
+        row_format_s += " |"
+
+        def format(*args):
+            return row_format_s.format(
+                *map(str, args), vwidth=vlength, bwidth=blength, awidth=alength
+            )
+
+        s = []
+
+        # First row:
+        s.append(format("", "b", *self.N))
+
+        # Length of a row:
+        lr = len(s[0])
+
+        # Separator:
+        s.append("-" * lr)
+
+        for xb in self.B:
+            s.append(format(xb, self.b[xb], *[self.a[xb][xn] for xn in self.N]))
+
+        s.append("-" * lr)
+        s.append(format("z", self.z, *[self.c[xn] for xn in self.N]))
+        s.append("-" * lr)
+
+        return "\n".join(s)