Re: set variable

[Aaron Hill]

On 2021-02-19 12:21 pm, Robert Kubosz wrote:
> Hello
>
> The default way to override an existing variable in scheme is:
> #(define foo 2)
> #(set! foo 3)
> #(display foo) %--> output is 3
>
> I want to override the foo with use of another variable storing the
> foo's varname:
>
> #(define foo 2)
> #(define bar 'foo) %variable storing the foo's varname
> #(set! `,bar 3)  %I want here to override the foo variable with use of 
> bar
> #(display foo) %---> the expected by me output is 3
>
> How can I do this?

The set! macro expects the variable to be changed.  On the other hand, 
module-set! expects a symbol naming the variable to be changed.  If you 
know the variable is within the current-module, you can do this:

%%%%
\version "2.22.0"

#(define xyzzy 123)
#(format #t "\nxyzzy = ~s" xyzzy)
#(set! xyzzy -456)
#(format #t "\nxyzzy = ~s" xyzzy)
#(module-set! (current-module) 'xyzzy 78.9)
#(format #t "\nxyzzy = ~s" xyzzy)
%%%%
====
Parsing...
xyzzy = 123
xyzzy = -456
xyzzy = 78.9
Success: compilation successfully completed
====


-- Aaron Hill