adapted to new overloading scheme

Demo/classes/Dates.py

@@ -16,7 +16,7 @@
 # Date objects support one visible method, date.weekday().  This returns
 # the day of the week the date falls on, as a string.
 #
-# Date objects also have 4 (conceptually) read-only data attributes:
+# Date objects also have 4 read-only data attributes:
 #   .month  in 1..12
 #   .day    in 1..31
 #   .year   int or long int
@@ -33,6 +33,11 @@
 # Tim Peters   tim@ksr.com
 # not speaking for Kendall Square Research Corp
 
+# Adapted to Python 1.1 (where some hacks to overcome coercion are unnecessary)
+# by Guido van Rossum
+
+# vi:set tabsize=8:
+
 _MONTH_NAMES = [ 'January', 'February', 'March', 'April', 'May',
 		 'June', 'July', 'August', 'September', 'October',
 		 'November', 'December' ]
@@ -81,6 +86,7 @@ def _num2date( n ):		# return date with ordinal n
 	raise TypeError, 'argument must be integer: ' + `type(n)`
 
     ans = Date(1,1,1)	# arguments irrelevant; just getting a Date obj
+    del ans.ord, ans.month, ans.day, ans.year # un-initialize it
     ans.ord = n
 
     n400 = (n-1)/_DI400Y		# # of 400-year blocks preceding
@@ -93,7 +99,7 @@ def _num2date( n ):		# return date with ordinal n
     year, n = year + more, int(n - dby)
 
     try: year = int(year)		# chop to int, if it fits
-    except ValueError: pass
+    except (ValueError, OverflowError): pass
 
     month = min( n/29 + 1, 12 )
     dbm = _days_before_month( month, year )
@@ -118,6 +124,12 @@ class Date:
 	self.month, self.day, self.year = month, day, year
 	self.ord = _date2num( self )
 
+    # don't allow setting existing attributes
+    def __setattr__( self, name, value ):
+	if self.__dict__.has_key(name):
+	    raise AttributeError, 'read-only attribute ' + name
+	self.__dict__[name] = value
+
     def __cmp__( self, other ):
 	return cmp( self.ord, other.ord )
 
@@ -132,52 +144,27 @@ class Date:
 	      self.day,
 	      _MONTH_NAMES[self.month-1] ) + `self.year`
 
-    # automatic coercion is a pain for date arithmetic, since e.g.
-    # date-date and date-int mean different things.  So, in order to
-    # sneak integers past Python's coercion rules without losing the info
-    # that they're really integers (& not dates!), integers are disguised
-    # as instances of the derived class _DisguisedInt.  That this works
-    # relies on undocumented behavior of Python's coercion rules.
-    def __coerce__( self, other ):
-	if type(other) in _INT_TYPES:
-	    return self, _DisguisedInt(other)
-	# if another Date, fine
-	if type(other) is type(self) and other.__class__ is Date:
-	    return self, other
-
-    # Python coerces int+date, but not date+int; in the former case,
-    # _DisguisedInt.__add__ handles it, so we only need to do
-    # date+int here
+    # Python 1.1 coerces neither int+date nor date+int
     def __add__( self, n ):
 	if type(n) not in _INT_TYPES:
 	    raise TypeError, 'can\'t add ' + `type(n)` + ' to date'
 	return _num2date( self.ord + n )
+    __radd__ = __add__ # handle int+date
 
-    # Python coerces all of int-date, date-int and date-date; the first
-    # case winds up in _DisguisedInt.__sub__, leaving the latter two
-    # for us
+    # Python 1.1 coerces neither date-int nor date-date
     def __sub__( self, other ):
-	if other.__class__ is _DisguisedInt:	# date-int
-	    return _num2date( self.ord - other.ord )
+	if type(other) in _INT_TYPES:		# date-int
+	    return _num2date( self.ord - other )
 	else:
 	    return self.ord - other.ord		# date-date
 
-    def weekday( self ):
-	return _num2day( self.ord )
-
-# see comments before Date.__add__
-class _DisguisedInt( Date ):
-    def __init__( self, n ):
-	self.ord = n
-
-    # handle int+date
-    def __add__( self, other ):
-	return other.__add__( self.ord )
-
     # complain about int-date
-    def __sub__( self, other ):
+    def __rsub__( self, other ):
 	raise TypeError, 'Can\'t subtract date from integer'
 
+    def weekday( self ):
+	return _num2day( self.ord )
+
 def today():
     import time
     local = time.localtime(time.time())
@@ -189,9 +176,7 @@ def test( firstyear, lastyear ):
     b = Date(9,30,1914)
     if `a` != 'Tue 30 Sep 1913':
 	raise DateTestError, '__repr__ failure'
-    if (not a < b) or a == b or a > b or b != b or \
-	  a != 698982 or 698982 != a or \
-	  (not a > 5) or (not 5 < a):
+    if (not a < b) or a == b or a > b or b != b:
 	raise DateTestError, '__cmp__ failure'
     if a+365 != b or 365+a != b:
 	raise DateTestError, '__add__ failure'

Demo/classes/Rat.py

 # Rational numbers
 
+from types import *
 
 def rat(num, den):
+	if type(num) == FloatType or type(den) == FloatType:
+		return num/den
 	return Rat(num, den)
 
 
@@ -16,12 +19,21 @@ class Rat:
 	def __init__(self, num, den):
 		if den == 0:
 			raise ZeroDivisionError, 'rat(x, 0)'
-		g = gcd(num, den)
+		if type(den) == FloatType or type(num) == FloatType:
+			g = float(den)
+		else:
+			g = gcd(num, den)
 		self.num = num/g
 		self.den = den/g
 
 	def __repr__(self):
-		return 'rat' + `self.num, self.den`
+		return 'Rat(%s, %s)' % (self.num, self.den)
+
+	def __str__(self):
+		if self.den == 1:
+			return str(self.num)
+		else:
+			return '%s/%s' % (self.num, self.den)
 
 	def __cmp__(a, b):
 		c = a-b
@@ -42,29 +54,23 @@ class Rat:
 
 	def __coerce__(a, b):
 		t = type(b)
-		if t == type(0):
-			return a, rat(b, 1)
-		if t == type(0L):
-			return a, rat(b, 1L)
-		if t == type(0.0):
-			return a.__float__(), b
-		if t == type(a) and a.__class__ == b.__class__:
+		if t == IntType:
+			return a, Rat(b, 1)
+		if t == LongType:
+			return a, Rat(b, 1L)
+		if t == FloatType:
+			return a, Rat(b, 1.0)
+		if t == InstanceType and a.__class__ == b.__class__:
 			return a, b
 		raise TypeError, 'Rat.__coerce__: bad other arg'
 
 	def __add__(a, b):
-		if type(b) <> type(a):
-			a, b = a.__coerce__(b)
-			return a + b
 		return rat(a.num*b.den + b.num*a.den, a.den*b.den)
 
 	def __sub__(a, b):
 		return rat(a.num*b.den - b.num*a.den, a.den*b.den)
 
 	def __mul__(a, b):
-		if type(b) <> type(a):
-			a, b = a.__coerce__(b)
-			return a * b
 		return rat(a.num*b.num, a.den*b.den)
 
 	def __div__(a, b):
@@ -75,21 +81,21 @@ class Rat:
 
 
 def test():
-	print rat(-1L, 1)
-	print rat(1, -1)
-	a = rat(1, 10)
+	print Rat(-1L, 1)
+	print Rat(1, -1)
+	a = Rat(1, 10)
 	print int(a), long(a), float(a)
-	b = rat(2, 5)
+	b = Rat(2, 5)
 	l = [a+b, a-b, a*b, a/b]
 	print l
 	l.sort()
 	print l
-	print rat(0, 1)
+	print Rat(0, 1)
 	print a+1
 	print a+1L
 	print a+1.0
 	try:
-		print rat(1, 0)
+		print Rat(1, 0)
 		raise SystemError, 'should have been ZeroDivisionError'
 	except ZeroDivisionError:
 		print 'OK'