Re: Octave's eval function

[David Bateman]

E. Joshua Rigler wrote:

> The following does what I want:
>
>  out=eval("if (~exist('tmp')) tmp=0; endif; tmp=tmp+1; tmp*5;");
>
> ...specifically, it evaluates the string to 1) initialize the variable
> tmp if it doesn't already exist; 2) increment tmp by 1 each time it is
> called; and 3) return tmp*5 to the variable out.
>
> Is the fact that eval appears to always return the result of the last
> expression in the string (i.e., tmp*5) strictly intentional?  I can't
> really tell from the help file.  This is exactly what I want, but I just
> want to be sure this behavior isn't likely to change anytime soon.
>
> I'm running 2.1.64 with the latest Forge.  Thanks,
>
> EJR
>  

Why do you need eval in the case above? It can be written directly 
without eval. "eval" seems to be returning "ans", which would explain 
your behaviour.

I'd also be inclined to write this slightly differently as

eval('tmp=tmp+1'; tmp*5;','tmp=0;'); out = ans;

since, it doesn't seem that the CATCH string can return an argument in 
octave 2.1.64 (perhaps this is a bug), and matlab can't return an 
argument in either string.

Regards
David

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