Better implementation of Expression.__repr__

[linpy.git] / pypol / linexprs.py

diff --git a/pypol/linexprs.py b/pypol/linexprs.py
index f3cff23..a9f188b 100644 (file)
--- a/pypol/linexprs.py
+++ b/pypol/linexprs.py
@@ -9,7 +9,7 @@ from fractions import Fraction, gcd
 
 __all__ = [
     'Expression',
 
 __all__ = [
     'Expression',

-    'Symbol', 'symbols', 'Dummy',
+    'Symbol', 'Dummy', 'symbols',

     'Rational',
 ]
 
     'Rational',
 ]
 


@@ -269,39 +269,27 @@ class Expression:
 
     def __repr__(self):
         string = ''
 
     def __repr__(self):
         string = ''

-        i = 0
-        for symbol in self.symbols:
-            coefficient = self.coefficient(symbol)
+        for i, (symbol, coefficient) in enumerate(self.coefficients()):

             if coefficient == 1:
             if coefficient == 1:

-                if i == 0:
-                    string += symbol.name
-                else:
-                    string += ' + {}'.format(symbol)
+                string += '' if i == 0 else ' + '
+                string += '{!r}'.format(symbol)

             elif coefficient == -1:
             elif coefficient == -1:

-                if i == 0:
-                    string += '-{}'.format(symbol)
-                else:
-                    string += ' - {}'.format(symbol)
+                string += '-' if i == 0 else ' - '
+                string += '{!r}'.format(symbol)

             else:
                 if i == 0:
             else:
                 if i == 0:

-                    string += '{}*{}'.format(coefficient, symbol)
+                    string += '{}*{!r}'.format(coefficient, symbol)

                 elif coefficient > 0:
                 elif coefficient > 0:

-                    string += ' + {}*{}'.format(coefficient, symbol)
+                    string += ' + {}*{!r}'.format(coefficient, symbol)

                 else:
                 else:

-                    assert coefficient < 0
-                    coefficient *= -1
-                    string += ' - {}*{}'.format(coefficient, symbol)
-            i += 1
+                    string += ' - {}*{!r}'.format(-coefficient, symbol)

         constant = self.constant
         constant = self.constant

-        if constant != 0 and i == 0:
+        if len(string) == 0:

             string += '{}'.format(constant)
         elif constant > 0:
             string += ' + {}'.format(constant)
         elif constant < 0:
             string += '{}'.format(constant)
         elif constant > 0:
             string += ' + {}'.format(constant)
         elif constant < 0:

-            constant *= -1
-            string += ' - {}'.format(constant)
-        if string == '':
-            string = '0'
+            string += ' - {}'.format(-constant)

         return string
 
     def _parenstr(self, always=False):
         return string
 
     def _parenstr(self, always=False):


@@ -406,21 +394,18 @@ class Symbol(Expression):
             return Symbol(node.id)
         raise SyntaxError('invalid syntax')
 
             return Symbol(node.id)
         raise SyntaxError('invalid syntax')
 

+    def __repr__(self):
+        return self.name
+

     @classmethod
     def fromsympy(cls, expr):
         import sympy
         if isinstance(expr, sympy.Symbol):
     @classmethod
     def fromsympy(cls, expr):
         import sympy
         if isinstance(expr, sympy.Symbol):

-            return Symbol(expr.name)
+            return cls(expr.name)

         else:
             raise TypeError('expr must be a sympy.Symbol instance')
 
 
         else:
             raise TypeError('expr must be a sympy.Symbol instance')
 
 

-def symbols(names):
-    if isinstance(names, str):
-        names = names.replace(',', ' ').split()
-    return tuple(Symbol(name) for name in names)
-
-

 class Dummy(Symbol):
 
     __slots__ = (
 class Dummy(Symbol):
 
     __slots__ = (


@@ -448,6 +433,15 @@ class Dummy(Symbol):
     def __eq__(self, other):
         return isinstance(other, Dummy) and self._index == other._index
 
     def __eq__(self, other):
         return isinstance(other, Dummy) and self._index == other._index
 

+    def __repr__(self):
+        return '_{}'.format(self.name)
+
+
+def symbols(names):
+    if isinstance(names, str):
+        names = names.replace(',', ' ').split()
+    return tuple(Symbol(name) for name in names)
+

 
 class Rational(Expression):
 
 
 class Rational(Expression):