Temporarily installs active bindings for a set of variable names in
env so that any write to those names during the evaluation of
expr_lang flips a corresponding *_lastupdate flag in env.
This flags assignments even when the value is overwritten with the same
value, and does not flag branches that are not executed.
with_write_flags_lang(expr_lang, tracked, env, flag_value = 1L)Invisibly returns NULL. The function works by side effects
(mutating env and its *_lastupdate flags).
A language object (call or expression) to evaluate.
For example, react_list[[i]][["react"]] returned by add_reactevt().
Character vector of top-level variable names to track
(e.g., c("q_default","c_default","curtime")). For each name nm,
an active binding is installed at env[[nm]], and writes set
env[[paste0(nm, "_lastupdate")]] <- flag_value.
Environment in which to install the bindings and evaluate
expr_lang (your per-patient/per-arm working environment).
Scalar written into each *_lastupdate when a write
occurs (commonly 1L; you may use a timestamp like env$curtime).
Active bindings add a tiny overhead per read/write of the tracked names
(a function call). Keep tracked small and the binding body minimal.
Install only for the duration of the block and tear down immediately
(handled for you). If your block performs many reads and few writes,
consider a snapshot-and-diff approach instead
Typical use: when accum_backwards = TRUE, wrap the evaluation of a
reaction/input block so you can later accumulate only inputs that were
actually written in that event.
The function creates a private backing store for tracked names and
installs active bindings in env. Reads return the stored value.
Writes (via <- or =) update the store and set the corresponding
*_lastupdate flag in env.
It does not zero the *_lastupdate flags; do that before calling
this function (typically once per event).
Only top-level symbols are tracked. To track obj$el <- ..., track
"obj" (the container) rather than "obj$el".
Active bindings are removed and plain symbols restored on exit, even if
an error occurs (via on.exit() teardown).