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Re: Quantity

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  • Subject: [mg131730] Re: Quantity
  • From: Bill Rowe <readnews at>
  • Date: Wed, 25 Sep 2013 02:35:45 -0400 (EDT)
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On 9/24/13 at 4:16 AM, itais at (Itai Seggev) wrote:

>On Sun, Sep 22, 2013 at 02:47:41AM -0400, Bill Rowe wrote:

>>There does not seem to be a specific set of unit strings. Note that

>>In[1]:= UnitConvert[Quantity[12., "Feet"], "Meters"]

>>Out[1]= 3.6576 m

>>returns a result essentially immediately. But doing

>>In[2]:= UnitConvert[Quantity[12., "Foot"], "Meters"]

>>Out[2]= 3.6576 m

>>returns the same result after a small delay. You should see a brief
>>message indicating Mathematica is interpreting the units. I believe
>>what is happening here is Mathematica is using Wolfram Alpha to
>>interpret the unit string which increases the allowable number of
>>unit strings significantly and makes it essentially impossible for
>>a user to create a list of allowable unit strings.

>I'm not sure if you are complaining about or praising the
>flexibility of input,

Neither. I was simply trying to show why it would be difficult
to enumerate a specific list of units Mathematica can utilize.

>but you can always see the canonical unit name
>by looking at the InputForm.

>In[3]:= Quantity[5, "Foot"]//InputForm
>Out[3]//InputForm=Quantity[5, "Feet"]

True. But this doesn't really answer the original poster's
question. Is there a method to create a list of unit strings
known to the kernel, i.e., those that would not involve a query
to Wolfram Alpha?

>You can also turn off internet connectivity in the preferences if
>you don't want Quantity to try to interpret units for you by asking

I am happy with Mathematica asking Wolfram Alpha. That generally
makes my life simpler. But I can also see why it might be nice
to have a list of unit strings Mathematica will work with
without asking Wolfram Alpha.

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