details: http://hg.sympy.org/sympy/rev/0a5e8fa81903
changeset: 1780:0a5e8fa81903
user: Robert <[EMAIL PROTECTED]>
date: Sat Feb 02 10:45:40 2008 +0100
description:
Implements Piecewise function (#353).
Ondrej: The patch didn't pass review, but Andy fixed that in the following
patch, so it goes in.
Signed-off-by: Robert <[EMAIL PROTECTED]>
Signed-off-by: Ondrej Certik <[EMAIL PROTECTED]>
diffs (85 lines):
diff -r a4a3dd165e1b -r 0a5e8fa81903 sympy/functions/__init__.py
--- a/sympy/functions/__init__.py Wed Oct 08 20:55:04 2008 +0200
+++ b/sympy/functions/__init__.py Sat Feb 02 10:45:40 2008 +0100
@@ -24,6 +24,7 @@
from elementary.exponential import exp, log, LambertW
from elementary.hyperbolic import sinh, cosh, tanh, coth, asinh, acosh, atanh,
acoth
from elementary.integers import floor, ceiling
+from elementary.piecewise import Piecewise
from special.error_functions import erf
from special.gamma_functions import gamma, lowergamma, uppergamma, polygamma,
loggamma
diff -r a4a3dd165e1b -r 0a5e8fa81903 sympy/functions/elementary/piecewise.py
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/sympy/functions/elementary/piecewise.py Sat Feb 02 10:45:40 2008 +0100
@@ -0,0 +1,52 @@
+from sympy import *
+
+
+class Piecewise(Function):
+ """
+ > Container for a Piecewise Function
+ -- Piecewise represents a piecewise function within the SymPy context.
+
+ Example Usage:
+
+ from sympy import Piecewise, oo, log, symbols
+ x = symbols('x')
+ p = Piecewise(x, [[(-oo, -1), 1], [(1, 2), x*x], [(3, oo), log(x)]])
+
+ Explanation:
+ - The first argument is the variable of the piecewise function.
+ - The second argument is a Python list of sublists.
+ - The first entry in the sublist is a tuple with the range of a function.
+ - The second entry is the actual function over the specified range.
+ """
+ nargs=1
+
+ def __new__(cls, *args, **options):
+ if cls is Function:
+ if len(args) == 1 and isinstance(args[0], str):
+ return FunctionClass(Function, *args)
+ else:
+ print args
+ print type(args[0])
+ raise Exception("You need to specify exactly one string")
+ args = map(Basic.sympify, args)
+ return Basic.__new__(cls, *args, **options)
+
+ def fdiff(self, arg=1):
+ """ Returns the differentiated piecewise function """
+ e = self.args[1]
+
+ for i in range(0, len(self.args[1])):
+ e[i][1] = diff(e[i][1], self.args[0])
+
+ def canonize(self, arg, elems):
+ arg = Basic.sympify(arg)
+ for x in self.elems:
+ cond = x[0]
+ if isinstance(cond, (Basic.Number, Basic.Number)):
+ if cond[0] <= arg and arg <= cond[1]:
+ return x[1]
+ else:
+ cond = Basic.sympify(cond)
+ if isinstance(cond, Bool):
+ if cond:
+ return x[1]
diff -r a4a3dd165e1b -r 0a5e8fa81903
sympy/functions/elementary/tests/test_piecewise.py
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/sympy/functions/elementary/tests/test_piecewise.py Sat Feb 02
10:45:40 2008 +0100
@@ -0,0 +1,14 @@
+from sympy import Piecewise, oo, log, symbols
+
+x = symbols('x')
+
+
+def test_piecewise():
+ p = Piecewise(x, [[(-oo, -1), 1], [(1, 2), x*x], [(3, oo), log(x)]])
+
+
+ p.fdiff()
+
+ assert p.args[1][0] == [(-oo, -1), 0]
+ assert p.args[1][1] == [(1, 2), 2*x]
+ assert p.args[1][2] == [(3, oo), 1/x]
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