Evaluating with a lexical environment
spibou at gmail.com
Thu Jul 11 18:44:46 UTC 2019
clisp provides a facility to evaluate a form in a non null lexical
environment. It works as follows
> (let ((a 1) (b 2))
(ext:eval-env '(format t "a is ~A b is ~A~%" a b) (ext:the-environment)))
a is 1 b is 2
The clisp documentation gives
Macro EXT:THE-ENVIRONMENT. As in Scheme, the macro (EXT:THE-ENVIRONMENT)
returns the current lexical environment. This works only in interpreted
code and is not compilable!
Function (EXT:EVAL-ENV form &OPTIONAL environment). evaluates a form in
a given lexical environment, just as if the form had been a part of the
program that the environment came from.
I was wondering if ECL has something analogous or could be added easily.
Looking in the ECL source I saw a si::eval-with-env function in file
ecl-16.1.3/src/c/compiler.d .If you do
> (find-symbol "EVAL-WITH-ENV" "SYSTEM")
which suggests that the function is not just for internal use. But scanning
the documentation , I didn't see it mentioned. I tried
(defmacro env-eval (form &environment env)
`(ext:eval-with-env ,form (quote ,env)))
> (let ((v 12)) (env-eval '(print v)))
The variable V is unbound.
Broken at EVAL.No restarts available.
Broken at EVAL.
So is there a way to achieve this ?
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