Re: [Help-bash] declare -i

[Dan Douglas]

On Wednesday, May 09, 2012 07:18:51 PM Bill Gradwohl wrote:
> 
> On Wed, May 9, 2012 at 2:55 PM, Greg Wooledge <address@hidden> wrote:
> 
> Math contexts do an infinitely-recursing indirect parameter expansion
> thingy:
> 
> imadev:~$ a=b b=c c=d d=e e=f f=42; echo $((a))
> 42
> 
> 
> Didn't know that you could write a=b b=c c=d d=e e=f f=42; as one statement. 
> I'll have to play with that to figure out who sets the return code (last I 
> presume), and if there's an assumed connector in between each expression. Is 
> there any return code checking from one to the next? I'll figure it out.

There's no "return codes". If a variable isn't a number then bash tries to 
resolve it recursively until it finds something that is.

> Didn't know about the infinite recursive expansion either.

It's limited to 1024.

> Thank You
> 
> The infinite recursion could come in handy in a non arithmetic context as 
> well. Why can't we have it everywhere?

It's used unintentionally more often than intentionally. I have a few uses for 
it which search at most a couple levels. You definitely don't want this 
everywhere.
Print Fibbonacci:  a=('a[a[n]=a[n-1]+a[n-2],n++/94]' 2 0 1); echo 
"address@hidden:n=4,a}"

> This brings to mind what happened the other day.  I tried array[-1]=blahBlah 
> and couldn't figure out what it was complaining about. A Google search 
> finally told me that's illegal on the left hand side. I guess I never tried 
> that before. I didn't notice anything in man bash about it.
> 
> I'd like the infinite recursion everywhere and [-1] on the left hand side as 
> examples of consistency as opposed to the exceptions they are currently.
> 
> -- 
> Bill Gradwohl

See my last mail. Bash can't do it (yet).

-- 
Dan Douglas

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