details: http://hg.sympy.org/sympy/rev/95089a89cabd
changeset: 1846:95089a89cabd
user: Andy R. Terrel <[EMAIL PROTECTED]>
date: Wed Oct 22 22:13:34 2008 +0200
description:
Adding ExprCondPair data structure to piecewise objects and cleaning code.
diffs (151 lines):
diff -r d072a7ea3a52 -r 95089a89cabd sympy/functions/elementary/piecewise.py
--- a/sympy/functions/elementary/piecewise.py Wed Oct 22 22:13:18 2008 +0200
+++ b/sympy/functions/elementary/piecewise.py Wed Oct 22 22:13:34 2008 +0200
@@ -1,9 +1,30 @@
from sympy.core.basic import Basic, S
-from sympy.core.function import Function, FunctionClass, diff
+from sympy.core.function import Function, diff
from sympy.core.numbers import Number
from sympy.core.relational import Relational
from sympy.core.sympify import sympify
+
+class ExprCondPair(Basic):
+ """Represents an expression, condition pair."""
+
+ def __new__(cls, expr, cond, **assumptions):
+ expr = sympify(expr)
+ cond = sympify(cond)
+ return Basic.__new__(cls, expr, cond, **assumptions)
+
+ @property
+ def expr(self):
+ return self.args[0]
+
+ @property
+ def cond(self):
+ return self.args[1]
+
+ def __iter__(self):
+ yield self.expr
+ yield self.cond
+
class Piecewise(Function):
"""
@@ -36,13 +57,21 @@
nargs=None
def __new__(cls, *args, **options):
- for opt in ["nargs", "dummy", "comparable", "noncommutative",
"commutative"]:
- if opt in options:
- del options[opt]
- r = cls.canonize(*args)
+ # Check types first
+ for ec in args:
+ if not isinstance(ec, tuple) or len(ec) != 2:
+ raise TypeError, "args may only include (expr, cond) pairs"
+ cond_type = type(ec[1])
+ if not (cond_type is bool or issubclass(cond_type, Relational) or \
+ issubclass(cond_type, Number)):
+ raise TypeError, \
+ "Cond %s is of type %s, but must be a bool," \
+ " Relational or Number" % (ec[1], cond_type)
# sympify args
- args = map(lambda x:(sympify(x[0]), sympify(x[1])), args)
+ args = map(lambda x:ExprCondPair(*x), args)
+
+ r = cls.canonize(*args)
if r is None:
return Basic.__new__(cls, *args, **options)
@@ -51,18 +80,6 @@
@classmethod
def canonize(cls, *args):
- # Check types first
- for ec in args:
- if (not isinstance(ec, tuple)) or len(ec)!=2:
- raise TypeError, "args may only include (expr, cond) pairs"
- for expr, cond in args:
- cond_type = type(ec[1])
- if cond_type != bool and not issubclass(cond_type, Relational) and\
- not issubclass(cond_type, Number):
- raise TypeError, \
- "Cond %s is of type %s, but must be a bool,"\
- " Relational or Number" % (cond, cond_type)
-
# Check for situations where we can evaluate the Piecewise object.
# 1) Hit an unevaluatable cond (e.g. x<1) -> keep object
# 2) Hit a true condition -> return that expr
@@ -117,7 +134,7 @@
# - eg x < 1, x < 3 -> [oo,1],[1,3] instead of [oo,1],[oo,3]
# 3) Sort the intervals to make it easier to find correct exprs
for expr, cond in self.args:
- if issubclass(type(cond),Number):
+ if cond.is_Number:
if cond:
default = expr
break
@@ -130,9 +147,9 @@
curr[1] = S.Infinity
else:
raise NotImplementedError, \
- "Currently only supporting evaluation with only "\
- "sym on one side fo the relation."
- curr = [max(a,curr[0]),min(b,curr[1])]
+ "Currently only supporting evaluation with only " \
+ "sym on one side of the relation."
+ curr = [max(a, curr[0]), min(b, curr[1])]
for n in xrange(len(int_expr)):
if self.__eval_cond(curr[0] < int_expr[n][1]) and \
self.__eval_cond(curr[0] >= int_expr[n][0]):
@@ -141,7 +158,7 @@
self.__eval_cond(curr[1] <= int_expr[n][1]):
curr[1] = int_expr[n][0]
if self.__eval_cond(curr[0] < curr[1]):
- int_expr.append(curr+[expr])
+ int_expr.append(curr + [expr])
int_expr.sort(key=lambda x:x[0])
# Add holes to list of intervals if there is a default value,
@@ -150,16 +167,16 @@
curr_low = a
for int_a, int_b, expr in int_expr:
if curr_low < int_a:
- holes.append([curr_low, min(b,int_a), default])
+ holes.append([curr_low, min(b, int_a), default])
curr_low = int_b
if curr_low > b:
break
if holes and default != None:
int_expr.extend(holes)
elif holes and default == None:
- raise ValueError, "Called interval evaluation over piecewise "\
- "function on undefined intervals %s" %\
- ", ".join([str((h[0],h[1])) for h in holes])
+ raise ValueError, "Called interval evaluation over piecewise " \
+ "function on undefined intervals %s" % \
+ ", ".join([str((h[0], h[1])) for h in holes])
# Finally run through the intervals and sum the evaluation.
# TODO: Either refactor this code or Integral.doit to call
_eval_interval
@@ -190,13 +207,8 @@
@classmethod
def __eval_cond(cls, cond):
"""Returns S.One if True, S.Zero if False, or None if undecidable."""
- if issubclass(type(cond), Number) or type(cond) == bool:
+ if type(cond) == bool or cond.is_Number:
return sympify(bool(cond))
- arg0 = cond.args[0]
- arg1 = cond.args[1]
- if isinstance(arg0, FunctionClass) or isinstance(arg1, FunctionClass):
- return None
- if not issubclass(type(arg0.evalf()), Number) or \
- not issubclass(type(arg1.evalf()), Number):
- return None
- return sympify(bool(cond))
+ if cond.args[0].is_Number and cond.args[1].is_Number:
+ return sympify(bool(cond))
+ return None
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