I'd like to have a project-wide variable which I can change during looking at that project. In other words, I'd like to get it affected whenever opening a file. Yes, I know .dir-locals.el exist in Emacs world. But I think it would be reset to the value set in .dir-locals.el whenever opening a file under that project.
Could I get some hints from you, please?
For this kind of thing you might want to use a function instead of a variable (directly). Specifically, use a getter and setter function.
All of your project code can invoke the getter function to get the value (which can be cached in a variable). And all of your code can invoke the setter function to change the value (which, again, can be cached in a variable).
These functions can be visible globally to your project. The cache variable would be accessed only by the getter and setter functions.
But as for code everywhere in your project being informed when the value gets updated and do what's appropriate with the new value whenever that happens, see #Phil's comment about the use of a variable - the same considerations apply.
You can have a hook in the setter function (or advise it), so that it does something additional (e.g. informs interested/subscribed code) whenever it updates the value.
For a variable you can do something similar using, as #Phils said in a comment, using add-variable-watcher.
For a user-option variable you can do something similar using :set and :get functions in the defcustom. (But those take effect only if changes are made using appropriate Customize functions or the Customize UI.)
You can eval in the dir-locals.el So, if you have a variable my-var that you want to be able to change with setq you could do something like
((nil . ((eval . (or (boundp 'my-var) (setq my-var 'default))))))
There are warnings about using eval in a dir-local though, since any code could be run there.
Related
In my project I use function, which calles find_library(...). Function is defined in SomeScript.cmake.
It works fine if called one time. But now I want to use it several time in my project. The problem is
that find_library caches the first result, and simply doesn`t run again.
So, the part I don't understand - function should provide it's own scope. But it looks like that there is,
only one "copy" of the function with all variables cached. Is it really so? And is there a correct way to use
find_library(...) inside a user function?
I am using MethodCall.setsField() to try to set an instance field on another instance.
My generated class that is doing the field-setting, GC, is trying to set the value of an instance field in an instance of something it has created (CI). So the field's declaring type is CI; my field-setting code resides in GC (which is in the same package as CI but otherwise unrelated to it).
The ByteBuddy checks seem to indicate that although GC and CI are in the same package, GC must be assignable to CI in order to set this field! That greatly surprised me, but I am not a bytecode expert, and I might very well be overlooking something obvious. Could someone kindly explain why this check is necessary?
The method call sets the field implicitly on the this instance on which the method is invoked. For this to be possible, a non-static field must be declared by a super type of the type on which the method is invoked.
If you think this is too strict, please file an issue with an example of the code you are trying to generate, including the code to generate it which is currently failing. Maybe I am not thinking straight about this and if there's a restriction to be lifted, I would surely do it.
I would like to share data between a plugin and my main function (this is, use it outside the call to the SCIPsolve function). For example, a branching rule sets a certain int variable to 1 and then, after the optimization is done I can go and check wether the variable was changes or not.
I thought I could accomplish this by using the plugin data (e.g. SCIP_BranchruleData) but it can't be accessed from outside the plugin's source file.
How can I do it?
I will appreciate any help.
Rodolfo
An easy solution is to add a getter function to the branchrule which you implement in branch_xyc.c and prototype in branch_xyz.h. Then your code needs to include the header file and you can access the fields in the branchdata.
See also the documentation of branch_allfullstrong.cpp where an external function is defined and you can see how to get the branchdata and branchrule when passing just a SCIP pointer.
I am programming in elisp, and I would like to associate a symbol with a function such that an attempt to access the variable instead calls the function. In particular, I want to trigger a special error message when lisp code attempts to access a certain variable. Is there a way to do this?
Example: suppose I want the variable current-time to evaluate to whatever (current-time-string) evaluates to at the time the variable is accessed. Is this possible?
Note that I do not control the code that attempts to access the variable, so that code could be compiled, so walking the tree and manually replacing variable accesses with function calls is not really an option.
You are looking for the Common Lisp define-symbol-macro.
Emacs Lisp lacks this feature, you cannot accomplish what you are trying to do.
However, not all is lost if you just want an error on accessing a variable.
Just makunbound it and access will error out (unless, of course, someone else nds it first).
I don't think you can do that.
As Sam says, define-symbol-macro would be the closest thing in Lisp (tho you make it sound like the accesses might be compiled beforehand, in which case even define-symbol-macro would be powerless). The closest thing in Elisp would be cl-symbol-macrolet, but that is even more limiting than define-symbol-macro since it has to be placed lexically around the accesses.
I've written a module to work with IBMs ClearCase through Powershell. At first it just contained a couple of often used functions, but now I'm expanding it. Most of the commands have to use a ClearTool object ($ct = new-object ClearCase.ClearTool), but I'd rather not have to recreate that object in every function call as it's a bit of overhead.
I also create a ClearCase view in many of these functions, but I can simply check for existence of the view and decide not to recreate it.
My question is, what's the best pattern for this? I can have a "create ct object" function and put the onus on the calling code to maintain it, but I don't think I like that method. Is it possible to have a module-wide variable for the ClearTool object and have Powershell check to see if it's filled before trying to recreate it each time?
Thanks!
In the end I created a couple of module-wide variables. I could hide them if necessary, although I haven't explicitly done that yet. I have a single function to create a view which must be called before doing any actual work and included in that is code to create the ClearTool object. I also have code to set the module-wide variables with the correct ClearTool object for use in other functions and the name of the view.
In the code of each of the functions if the ClearTool object ($ct) has not yet been set, they return an error condition.