What is the best way to deal with symbolic functions from R^n to R^m? A
symbolic vector? Note some of the following ways that do not work. I'm
not sure how I would specify that a given function f: R^2->R^2, for
example, had input variables x and y (if, say, I wanted to define it
f(x,y)=vector([x-y+c, x+2*c]) )
sage: var('x,y')
(x, y)
sage: f(x,y)=(x+y,x-2*y)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
/home/grout/.sage/temp/good/18016/_home_grout__sage_init_sage_0.py in
<module>()
/home/grout/sage/local/lib/python2.5/site-packages/sage/calculus/all.pyc
in symbolic_expression(x)
73 if isinstance(x, Expression):
74 return x
---> 75 return SR(x)
76
77 import desolvers
/home/grout/sage/local/lib/python2.5/site-packages/sage/calculus/calculus.pyc
in __call__(self, x)
452 msg, s, pos = err.args
453 raise TypeError, "%s: %s !!! %s" % (msg,
s[:pos], s[pos:])
--> 454 return self._coerce_impl(x)
455
456 def _coerce_impl(self, x):
/home/grout/sage/local/lib/python2.5/site-packages/sage/calculus/calculus.pyc
in _coerce_impl(self, x)
513 return self(x._sage_())
514 else:
--> 515 raise TypeError, "cannot coerce type '%s' into a
SymbolicExpression."%type(x)
516
517 def _repr_(self):
TypeError: cannot coerce type '<type 'tuple'>' into a SymbolicExpression.
sage: f=(x+y,x-2*y)
sage: f(x=2,y=3)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
/home/grout/.sage/temp/good/18016/_home_grout__sage_init_sage_0.py in
<module>()
TypeError: 'tuple' object is not callable
sage: f=vector((x+y,x-2*y))
sage: f(x=2,y=3)
(5, -4)
Jason
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