Re: Do loops in Mathematica

• To: mathgroup at smc.vnet.net
• Subject: [mg55177] Re: Do loops in Mathematica
• From: Jon Harrop <usenet at jdh30.plus.com>
• Date: Wed, 16 Mar 2005 05:35:53 -0500 (EST)
• References: <d15s6o\$9l2\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```dumb_founded wrote:
> I am having trouble setting up Do loops in Mathematica.  Even when I
> put in a return statement, I get no output.  Below is a concrete
> example of code I am putting in:
>
> Do[{p = Solve[x^2 + 3*x + 1 == 0, x], Return[2*p]}, {i, 1}]
>
> I get nothing out of it.

Yes, by using "Do" you are asking Mathematica to repeatedly do something and

In[1]:= Table[{p = Solve[x^2 + 3*x + 1 == 0, x], Return[2*p]}, {i, 1}]

-3 - Sqrt[5]         -3 + Sqrt[5]
Out[1]= {{{{x -> ------------}, {x -> ------------}},
2                    2

-3 - Sqrt[5]             -3 + Sqrt[5]
>     Return[{{2 (x -> ------------)}, {2 (x -> ------------)}}]}}
2                        2

In computer science terminology, it could be said that "Do" is an imperative
construct and "Table" is a functional construct.

> I am having a headache figuring out this simple chore.  Mathematica
> simply refuses to behave.

Mathematica is doing precisely what you ask it to do.

--
Dr Jon D Harrop, Flying Frog Consultancy
http://www.ffconsultancy.com

```

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