Thank you. I posted this question on SO in the meantime as well, but there is no answer for my question, so I pasted your answer (https://stackoverflow.com/questions/70517625/how-to-use-trace-for-function-in-parent-or-child-environment). Hope it is fine for you.
śr., 29 gru 2021 o 11:24 Duncan Murdoch <[email protected]> napisał(a): > > On 28/12/2021 4:21 p.m., Grzegorz Smoliński wrote: > > Thank you for all the comments. If this is not a problem, I would like > > to continue this thread as for me a lot of questions are still open. > > But if I should post other questions in different messages / topics, > > please let me know. > > > > I didn’t answer Ivan’s question previously, but yes, my desired result > > is indeed what debug() / debugonce() does and Ivan mentioned trace() > > earlier also, so I have tried this. I thought that trace() will be > > better in my case (than debug()) since I would like to be able to call > > trace() from one environment and insert browser() (using trace()) to > > the function defined in parent environment (still not sure if I > > understand this concept of environments). > > > > Even if I would like to use it in an shiny app, I have started with > > this example: > > > > ------------------------------ > > > > fun1 <- function() { > > a <- 1 > > a > > } > > > > fun2 <- function() { > > fun1 <- function(){ > > b <- 2 > > b > > } > > trace(fun1, browser, where = globalenv()) > > } > > > > fun1() > > fun2() > > fun1() > > > > -------------------------------- > > > > So I was hoping to use trace inside child environment of global env, > > i.e. set browser() using trace() to the body of function defined in > > parent environment, but for sure I do not understand this since > > trace() in my example above is putting the browser() function inside > > fun1() function defined not in global environment, but in the body of > > fun2(). I.e. I'm starting to browse the fun1() function with the local > > variable 'b', not 'a' as I wanted. > > You are being bitten by normal R scoping. While fun2 is executing, as > soon as it executes the fun1 assignment the name fun1 is bound to the > local function, so when you use fun1 in the first argument to trace(), > you get that one. It will ignore then "where" argument because it was > passed a function object. If you quote the name it will have to do a > lookup and it will use "where". So write fun2 like this: > > fun2 <- function() { > fun1 <- function(){ > b <- 2 > b > } > trace("fun1", browser, where = globalenv()) > } > > > > > > Can I ask for help with this? In other words, how can I refer to some > > function from the parent environment (not necessarily defined in the > > global environment) being in the child environment? > > You could have used parent.frame() in place of globalenv() if you want a > function that was visible to the caller of fun2. If you want a function > that was defined with the same environment as fun2, you can usually use > environment(fun2), or parent.env(environment()). > > > > > > Also, if I could ask - is the reversed operation possible? I mean - > > can I refer to some function from the child environment being in the > > parent environment? I guess not, because of ephemerality? > > Sometimes you can, but not usually. If fun2 had returned a value that > referenced the evaluation frame, you would be able to see the "b" > version of fun1 there. But yours didn't. This one would: > > > fun2 <- function() { > fun1 <- function(){ > b <- 2 > b > } > trace("fun1", browser, where = globalenv()) > environment() > } > > Now if you do e <- fun2(), you'll set the trace on the global fun1, but > e$fun1 will be the local one. > > I don't really know how Shiny sets things up, so I can't help with the > stuff below. > > Duncan Murdoch > > > > > > As I mentioned, I'm thinking about all of this in the context of shiny > > app and the shiny app which consists of multiple files, modules. I'm > > thinking if I could refer to any function from any environment (or at > > least to any function in any parent environment) from one place (one, > > current environment) where I will call debug() or trace() to insert > > browser() at the beginning of this chosen function. And by "any > > function" I'm thinking about another thing problematic for me. If I > > consider this example: > > > > ------------------------------- > > mod.R inside R/ > > --- > > > > mod_UI <- function(id) { > > } > > > > name_mod <- function(input, output, session) { > > fun1 <- reactive({ > > a <- 1 > > }) > > } > > > > --- > > app.R > > --- > > > > library(shiny) > > > > ui <- fluidPage( > > mod_UI("mod"), > > textOutput("env") > > ) > > > > server <- function(input, output, session) { > > > > name_mod("mod") > > > > output$env <- renderPrint({ > > names(environment(name_mod)) > > }) > > > > observe({ > > #trace(fun1, browser, where = environment(name_mod)) > > }) > > } > > > > shinyApp(ui, server) > > --------------------------------------- > > I tried to refer to the fun1 in environment(name_mod) - if I'm not > > wrong, this is my parent environment, where objects "mod_UI" and > > "name_mod" exist, but obviously I'm doing this wrong, right? Because > > here: "#trace(fun1, browser, where = environment(name_mod))" I have > > tried to refer to the module environment, but I should refer to the > > environment inside "name_mod". I don't know how to do this and here I > > also would like to ask for help. > > > > I know this may not be the best place for questions regarding shiny, > > but I think these questions are purely linked to environment topics. > > > > I also remember Bert's post about "body()" and yes, this seems to be a > > better idea than my first try in my first post, but "trace()" and > > "debug()" seem much easier as all I want is to insert browser(). But I > > just can't get it, how to refer to functions in (any) other > > environments. > > > > Thank you very much for all your help and I hope it is OK to keep asking :). > > > > pon., 27 gru 2021 o 18:28 Duncan Murdoch <[email protected]> > > napisał(a): > >> > >> On 27/12/2021 8:25 a.m., Duncan Murdoch wrote: > >>> On 27/12/2021 8:06 a.m., Grzegorz Smoliński wrote: > >>>> Hi, > >>>> > >>>> I know it is possible to find the environment in which some object > >>>> lives using the 'environment()' function and the name of this object, > >>>> but how to modify code of this object after this? Below is MRE: > >>> > >>> You are misunderstanding the relation between environments and > >>> functions. However, your understanding is also being messed up by a bug > >>> in R, so it's not entirely your fault. > >> > >> Actually this isn't a bug in R, it is working as documented. For a > >> detailed explanation, see the response to my bug report here: > >> https://bugs.r-project.org/show_bug.cgi?id=18269 . > >> > >> For a quick idea: "complex assignments" are assignments where there is > >> a complex expression on the left hand side, e.g. > >> > >> environment(test)$test <- ... > >> > >> The way these are documented to work (in the R Language Definition > >> manual) makes intuitive sense when you are working with regular R > >> objects, but environments are "mutable" objects: assigning them to a > >> new name doesn't make a new copy, just a new reference. That causes the > >> definition of the complex assignment above to work in an unintuitive way. > >> > >> Conclusion: you should avoid using calls like environment(f) on the > >> left hand side of assignments, especially as part of a larger > >> expression. Break up the statement into steps like I did below: > >> > >>> e <- environment(test) > >>> e$test <- eval(parse(text = "function() 2")) > >> > >> The same advice would apply to a function that returned an R6 object or > >> a mutable object from the methods package (which are really environments > >> in disguise), as well as some other exotic objects. > >> > >> Duncan Murdoch > > > > ______________________________________________ > > [email protected] mailing list -- To UNSUBSCRIBE and more, see > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > > and provide commented, minimal, self-contained, reproducible code. > ______________________________________________ [email protected] mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
