Compile-variable and compile-assignment with lexical-address instructions
Using
find-variable
from exercise
5.41
, rewrite
compile-variable
and
compile-assignment
to output lexical-address instructions. In cases where
find-variable
returns
not-found
(that is, where the variable is not in the compile-time environment), you should have the code generators use the evaluator operations, as before, to search for the binding. (The only place a variable that is not found at compile time can be is in the global environment, which is part of the run-time environment but is not part of the compile-time environment. Thus, if you wish, you may have the evaluator operations look directly in the global environment, which can be obtained with the operation
(op get-global-environment)
, instead of having them search the whole run-time environment found in
env
.) Test the modified compiler on a few simple cases, such as the nested
lambda
combination at the beginning of this section.