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Topic: rookie code issue
Replies: 3   Last Post: Mar 21, 2013 12:55 AM

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Bill Rowe

Posts: 1,647
Registered: 3/14/08
Re: rookie code issue
Posted: Mar 21, 2013 12:54 AM
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On 3/20/13 at 4:22 AM, wrote:

>Why doesn't the following code return a 2?

>m = Cos; Which[m == Sin, 5, m == Cos, 2]


In[3]:= Head /@ {Cos, Sin}

Out[3]= {Symbol,Symbol}

So, by using Equal, you are asking Mathematica to determine
whether two symbols without assigned values are equal which it
cannot do.

What you want to use here is SameQ rather than Equal. That is

In[4]:= m = Cos;
Which[m === Sin, 5, m === Cos, 2]

Out[5]= 2

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