Use references instead of clones - #8
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These are considered mostly safe when proper cons pairs are added, although they don't work right now. More unsafe expressions were noted in commit 9ddd84d. * Change parameter types of 'env_bind' and 'env_bind_global', remove 'const' qualifier from 'val' parameter. * Store references instead of clones in 'env_bind' and 'env_bind_global'. * Return reference instead of clone in 'env_get'. * Don't clone self-evaluating expressions in 'eval'. * Don't clone returned expression in 'prim_print_str'.
* Don't clone expressions when cloning an environment. * Don't clone expressions of the body when cloning a lambda. * Don't mark 'g_nil', 'g_tru' and 'g_debug_trace_list' for garbage collection. * Don't clone expressions in 'cons', 'car', 'cdr' and 'nth' primitives. * Don't clone expressions when evaluating quoted (or backquoted) expressions.
The code of this commit is a bit messy, as explained in the comments. * Add 'is_used' member to 'Env', for storing whether or not it's being used somewhere else. * Unmark environments in 'gc_unmark_all'. * Mark environments in 'gc_mark_expr'. * Don't collect expressions if their associated environment is still in use.
This commit doesn't currently work, because we still work with copies.
From 'gc_mark_expr'.
Environment closures. Changes: * Add 'is_used' member to 'Env', for storing whether or not it's being used somewhere else. * Unmark environments in 'gc_unmark_all' (by setting 'is_used'). * Mark environments in 'gc_mark_expr' as used. * Don't collect expressions if their associated environment is marked as in use. * Set the parent environment on lambda creation, instead of on call. * Mark each expression of a lambda's environment whenever the lambda is marked for garbage collection. * Add 'pool_item_is_gcmarked', move 'pool_item_is_free' to 'expr_pool.h', make arguments of 'pool_item_flags' constant.
Before this commit, we just marked the lambda's environment and its contents. Now we also mark all parent environments, and their contents. After this commit, the Y combinator can be evaluated.
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Work with references, instead of always returning copies. This change was possible thanks to #5 (which needed #4), #6 and #7. Some changes were merged into this
copy-referencesbranch in #7.Major changes:
expr_clone, for working with references instead of copies.car,cdr,cons,nth,quoteandbackquoteprimitives.is_usedmember toEnv. Mostly included in Environment closures #7, but not completely (see 5758c96).g_nil,g_truandg_debug_trace_list) for garbage collection, since their references are being stored in the environment.Minor changes:
gc_mark_envandgc_mark_env_and_parentsstatic functions togarbage_collector.c.Env*parameter tolambdactx_init, remove it fromlambdactx_eval_body.Expr*parameter ofenv_bindandenv_bind_globalconstant.test/lambdas.lisp. See Environment closures #7.