Re: Query regarding Function

• To: mathgroup at smc.vnet.net
• Subject: [mg130137] Re: Query regarding Function
• From: David Bailey <dave at removedbailey.co.uk>
• Date: Wed, 13 Mar 2013 04:21:08 -0400 (EDT)
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```[This thread is now closed.  There have been enough answers. - Moderator]

On 12/03/2013 04:34, Rahul Chakraborty wrote:
> Dear all,
>
> Case1:  In the following code
>
>    Clear[f,x,y]
> g=Function[{x,y},x^2+2xy][b,a]
>
>   The output is found to be  b^2+2 xy
>
> Case2:  But for the code
>
>   Clear[f,x,y]
> g=Function[{x,y},x^2+2y][b,a]
>
>   The output is 2 a+b^2
>
>   Hence my query is why in case 1 x*y is not replaced by b and a whereas in case 2 it got replaced ?
>
> Regards,
>   rc
>
Variable names in Mathemnatica can be more than one character long -
remember that computer algebra can require a lot of variables! Thus xy
is a quite distinct variable - space the two characters out to get a
product: x y .

Note that it is always useful to examine dubious expressions using
FullForm (possibly with Hold to prevent evaluation) to determine their
true structure. This resolved a host of puzzles:

In[1]:= x y //FullForm
Out[1]//FullForm= Times[x,y]

In[2]:= xy //FullForm
Out[2]//FullForm= xy

In[3]:= x*y //FullForm
Out[3]//FullForm= Times[x,y]

David Bailey
http://www.dbaileyconsultancy.co.uk

```

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