[LON-CAPA-users] More elegant conditional text?

[Gerd Kortemeyer]

Hi,

On Feb 7, 2008, at 7:46 PM, Ray Batchelor wrote:
>
> <script type="loncapa/perl">$a='$ \mathrm{KE}_1=(1/2)M_1v_1^2 $';
> $b='$ \mathrm{E}_2=M_2c^2 $';
> $c='$ \mathrm{P}_3=M_3v_3^2 $';
>
> $choice=&random(0,2,1);
>
> @array=($a,$b,$c);</script>
> <startouttext /><p><m eval="on"> $array[$choice] </m></ 
> p><endouttext />
>
> Possibly someone can tell me that this is not robust?

I believe it's equally robust. Incorporating Ray's solution, we have  
four magic incantations:

<problem>
<script type="loncapa/perl">
$array[1] = '<m>$E=mc^2$</m>';
$array[2] = &xmlparse('<m>$\nabla E=\varrho/\varepsilon_0$</m>');
$array[3] = '$E=mv^2/2$';
$array[4] = '\nabla\times E=-\partial B/\partial t';
</script>
<startouttext />
It is <parse>$array[1]</parse>, but also <display>$array[2]</display>  
- strange.
And there is always <m eval="on">$array[3]</m> and <m eval="on">$  
$array[4] $</m>.
<endouttext />
</problem>

As always in LON-CAPA, the number of possibilities is limitless ...  
or at least four.

- Gerd.