       Re: Do loops in Mathematica

• To: mathgroup at smc.vnet.net
• Subject: [mg55174] Re: Do loops in Mathematica
• From: dh <dh at metrohm.ch>
• Date: Wed, 16 Mar 2005 05:35:50 -0500 (EST)
• References: <d15s6o\$9l2\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi,
it looks like a bug to me. However,your Do loop is certainly written
rather strange. The way to do it (and that works!):

Do[p = Solve[x2 + 3*x + 1 == 0, x]; Return[2*p], {i, 1}]

Some notes concerning your original Do loop:Do[{p = Solve[x^2 + 3*x + 1
== 0, x], Return[2*p]}, {i, 1}]:
The List {..} does not make sense.
It does not make sense to multiply a replacement rule by 2: Return[2*p]

Daniel

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.
>
> Here is a sketch of the code I want to construct but am scared to
> because of the above problem I keep encountering.
>
> (1) the first expression in the Do loop calls the FindRoot function on
> nonlinear function of x that involves a constant c.  The constant c is
> in curly brackets at the end of the Do loop specifying a beginning
> value for c and an ending value for c.
> (2) I take the root found in the previous expression and I use it to
> calculate two numerical integrals
> (3) I add or subtract the two numerical integrals found in the previous
> expressions and I return the value of this expression (and this
> expression alone).
>
>
> I am having a headache figuring out this simple chore.  Mathematica
> simply refuses to behave.
>

```

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