Re: How do you control evaluation when using apply?
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- Subject: [mg130803] Re: How do you control evaluation when using apply?
- From: Christoph Lhotka <christoph.lhotka at univie.ac.at>
- Date: Fri, 17 May 2013 04:33:46 -0400 (EDT)
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Hello, both of your versions work fine in M9. Here is even a shorter one: In[]:= jacFun[func_, vars_] := Module[{f}, f = Function @@ {{x, y}, D[func, {vars}]}; f @@ # &] In[]:=jacFun[{Sin[x y], Cos[x + y]}, {x, y}][{10, 2}] Out[]:={{2 Cos[20], 10 Cos[20]}, {-Sin[12], -Sin[12]}} BR, Christoph On 05/16/2013 09:28 AM, Brentt wrote: > Why does this work > > In[0]: = jacobianFunction[func_, vars_List] := Module[{f}, > f = Function[Evaluate[vars], Evaluate[D[func, {vars}]]]; > f > ]; > jacobianFunction[{Sin[x y], Cos[x + y]}, {x, y}] @@ {10, 2} > > out[0]:= {{2 Cos[20], 10 Cos[20]}, {-Sin[12], -Sin[12]}} > > But this does not (the goal is to make the function take a point as an > argument) > > > In[0]: = jacobianFunction[func_, vars_List] := Module[{f}, > f = Evaluate[Function[Evaluate[vars], Evaluate[D[func, {vars}]]]]; > f@@ # & > ]; > jacobianFunction[{Sin[x y], Cos[x + y]}, {x, y}][{10, 2}] > > > > I can't get f@@ # & to evaluate properly (I've tried wrapping it in > ReleaseHold and evaluate statements, nothing seems to get it to evaluate. > > I know I can just rewrite the function to take the point but I'm just > curious why it won't work. > >
- References:
- How do you control evaluation when using apply?
- From: Brentt <brenttnewman@gmail.com>
- How do you control evaluation when using apply?