Peter Silcock <peter@fastmail.uk> writes:

> As a newcomer to Guile/Scheme, I am working my way through some
> exercises which require the use of an (assertion-violation) procedure
> to trap an error condition, specifically:
>
> (if (empty? queue)
>     (assertion-violation 'getq "Queue is empty")))
>
> When I run the code (which I have checked with the answer given in the
> book), I am presented with the following output: "In procedure module-
> lookup: Unbound variable: assertion-violation."
>
> So far I have found no pointers to a solution in the reference manual
> or on the web.  My assumption is that I am missing a module or library
> from somewhere, but don't know how to set about identifying it. Chicken
> Scheme also responds with the same error.
>
> Guile version 2.0.13 on Debian Stretch 4.9.0-3-amd64.
>
> Any suggestions please? Thanks in anticipation,
>
> Peter Silcock

I think you have to import the r6rs base library:

  (use-modules (rnrs base))

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