sperber at informatik.uni-tuebingen.de
Thu Apr 13 13:25:06 EDT 2006
Here are my suggestions for eval:
- Keep `eval' itself much like it is.
- Ditch `null-environment'.
- Add a procedure
where library-specifier is whatever the library proposal uses to
identify a library (currently a string).
This returns a specifier for an environment that contains all the
bindings in the named library. As with `scheme-report-environment',
the effect of assigning a variable bound in a library environment is
unspecified, as is the effect of evaluating non-expression programs.
Probably, `scheme-report-environment' could be defined in terms of
`library-environment' by making available libraries that correspond
to whatever we want it to correspond to.
- Add a procedure
that takes an S-expression representing a library definition (which
will presumably still exist, even after the changes to the library
mechanism), and makes the library available in the running program.
- Do we want to offer a library corresponding mostly to R5RS? (I'd
- Do we want to omit `scheme-report-environment' altogether. (I'd say
no, keep, at least for 5 argument.)
- Do we want to specify (scheme-report-environment 6)? (I'd say no.)
- Do we want to restrict the set of libraries available through
`library-environment'? My inclinication is to say that at least the
library the reference to eval is in, and the libraries imported by
it must be available, and more libraries can be made available
through an implementation-specific mechanism. (Which we'd strongly
encourage implementors to provide.) This way people can ship sets
of libraries or applications containing calls to `eval' without
having to include everything that's, say, in the development system.
- Do we want to crack down on programs that assign to library
variables or contain top-level definitions? My inclinination is to
say that the behavior is unspecified. We might restrict
implementations to one of two choices: either run the code as if
appended to the library body, or raise a specified exception, say
&eval-assignment or &eval-definition. I'd be in favor of that.
Cheers =8-} Mike
Friede, Völkerverständigung und überhaupt blabla
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