Redirect trace output to a file, even within events
See open-trace-file for a utility that redirects trace output to a file. The utility, open-trace-file!, is similar, but
differs from open-trace-file in the following two ways.
- You can use open-trace-file! within make-event forms, and
thereby within books.
- An active trust tag is required (see defttag) when calling
For example, we can open a trace file as follows, but the second form fails
to open a trace file if open-trace-file! is replaced by
(pprogn (open-trace-file! "xx")
(value '(value-triple nil))))