Re: Define variable only if it doesn't exist / is unbound

[Simon Albrecht]

On 29.03.19 12:11, David Kastrup wrote:
> Pedro Pessoa <address@hidden> writes:
>
> > Hello,
> > I want to init a variable only if it isn't bound. This seems a simple
> > matter, I was surpised I couldn't do it.
> > The thing is that it throws an 'unbound variable error' with anything I try.
> > I imagined something like:
> >
> > %%% pseudo
> > #(define var
> >      (not (is-bound? var) 0))
> > %%%
> var = 0
>
> Does it need to be in Scheme?

The difference is that
var = 0
overwrites any previous binding, and I guess that’s what Pedro wanted to 
avoid. (?)

Best, Simon