I want to read a table inside a Lua file before executing it. Is there a way to do this with loadfile. It returns only a function and I can't seem to be able to read what is inside (what is declared but not executed).
The other option I tried is to check if the environment changed, but yet again I couldn't read inside the function returned by loadfile().
Is there a way to do this without opening the file as text and searching the table?
Here is an example of the table I try to retrieve:
--file to be loaded
local library = require("library") --random requires...
table = { author = "myself", dependencies = "library > 1.0"} --table to get before execution
What you want is not possible.
There are no declarations in Lua, only executable statements.
You need to execute a script to see what it does.
However, you could read the file as text and try to extract the info you need using pattern matching. This won't be foolproof but it'll probably work in most cases if the files are written in the same way.
Related
I have an nspire calculator and after writing a hash table implementation, found the BASIC environment to be a pretty offensive programming environment. Unfortunately, as far as I'm aware, it's impossible to use Lua to write libraries.
I did see that somewhere in the Lua interface you can detect variable changes so it might be possible within a file to use Lua functions, but I fear it will go out of scope if used externally.
Is there a better way to do this?
It's not impossible to write Lua libraries for a TI-Nspire. You can put the libraries code into a string, store it as a variable in TI-Basic and put the file in the MyLibs folder. Then, when you want to load your library, do loadstring(var.recall("libfilename/programstring"))(). This will load the library's code as a string from that files, compile it (using loadstring), and execute it (practicaly the same as require).
Also, about getting from controlling a Lua script using TI-Basic, depending on what you want to do, you could use math.eval("<some TI-Basic code>"). This will execute the code in TI-Basic, and return the result as a Lua value (or string). This way, you can call a TI-Basic function every once in a while, and act according to its output.
I want to make a small "library" to be used by my future maxima scripts, but I am not quite sure on how to proceed (I use wxMaxima). Maxima's documentation covers the save(), load() and loadFile() functions, yet does not provide examples. Therefore, I am not sure whether I am using the proper/best way or not. My current solution, which is based on this post, stores my library in the *.lisp format.
As a simple example, let's say that my library defines the cosSin(x) function. I open a new session and define this function as
(%i0) cosSin(x) := cos(x) * sin(x);
I then save it to a lisp file located in the /tmp/ directory.
(%i1) save("/tmp/lib.lisp");
I then open a new instance of maxima and load the library
(%i0) loadfile("/tmp/lib.lisp");
The cosSin(x) is now defined and can be called
(%i1) cosSin(%pi/4)
(%o1) 1/2
However, I noticed that a substantial number of the libraries shipped with maxima are of *.mac format: the /usr/share/maxima/5.37.2/share/ directory contains 428 *.mac files and 516 *.lisp files. Is it a better format? How would I generate such files?
More generally, what are the different ways a library can be saved and loaded? What is the recommended approach?
Usually people put the functions they need in a file name something.mac and then load("something.mac"); loads the functions into Maxima.
A file can contain any number of functions. A file can load other files, so if you have somethingA.mac and somethingB.mac, then you can have another file that just says load("somethingA.mac"); load("somethingB.mac");.
One can also create Lisp files and load them too, but it is not required to write functions in Lisp.
Unless you are specifically interested in writing Lisp functions, my advice is to write your functions in the Maxima language and put them in a file, using an ordinary text editor. Also, I recommend that you don't use save to save the functions to a file as Lisp code; just type the functions into a file, as Maxima code, with a plain text editor.
Take a look at the files in share to get a feeling for how other people have gone about it. I am looking right now at share/contrib/ggf.mac and I see it has a lengthy comment header describing its purpose -- such comments are always a good idea.
For principiants, like me,
Menu Edit:configure:Startup commands
Copy all the functions you have verified in the first box (this will write your wxmaxima-init.mac in the location indicated below)
Restart Wxmaxima.
Now you can access the functions whitout any load() command
I have a spss syntax file that I need to run on multiple files each in a different directory with the same name as the file, and I am trying to too do this automatically. So far I have tried doing it with syntax code and am trying to avoid doing python is spss, but all I have been able to get is the code bellow which does not work.
VECTOR v = key.
LOOP #i = 1 to 41.
GET
FILE=CONCAT('C:\Users\myDir\otherDir\anotherDir\output\',v(#i),'\',v(#i),'.sav').
DATASET NAME Data#i WINDOW=FRONT.
*Do stuff to the opened file
END LOOP.
EXE.
key is the only column in a file that contains all the names of the files.
I am having trouble debugging since I don't know how to print to the screen if it is possible. So my question is: is there a way to get the code above to work, or another option that accomplishes the same thing?
You can't use an expression like that on a GET command. There are two choices. Use the macro language to put this together (see DEFINE in the Command Syntax Reference via the Help menu) or use the SPSSINC PROCESS FILES extension command or your own Python code to select the files with a wildcard.
The extension command or a Python program require the free Python Essentials available from the SPSS Community website or available with your Statistics version.
I'm planning to do a program with Lua that will first of all read specific files
and get information from those files. So my first question is whats the "my documents" path name? I have searched a lot of places, but I'm unable to find anything. My second question is how can I use the first four letters of a file name to see which one is the newest made?
Finding the files in "my documents" then find the newest created file and read it.
The reading part shouldn't be a problem, but navigating to "my documents" and finding the newest created file in a folder.
For your first question, depends how robust you want your script to be. You could use Lua's builtin os.getenv() to get a variety of environment vars related to user, such as USERNAME, USERPROFILE, HOMEDRIVE, HOMEPATH. Example:
username = os.getenv('USERNAME')
dir = 'C:\\users\\' .. username .. '\\Documents'
For the second question, there is no builtin mechanism in Windows to have the file creation or modification timestamp as part of the filename. You could read the creation or modification timestamp, via a C extension you create or using an existing Lua library like lfs. Or you could read the contents of a folder and parse the filenames if they were named according to the pattern you mention. Again there is nothing built into Lua to do this, you would either use os.execute() or lfs or, again, your own C extension module, or combinations of these.
I am using the C Fuzzy API and I want to load function module contained in a file lets say mycalculator.lua. This seem to run fine however when I later try to run another file A.lua that requires 'mycalculator' it does not work unless the mycalculator.lua file is available on the file system to reload. I am trying to just load it into the system and then have it available without having the mycalculator.lua in the file system. It there any way to have lua system keep the definition without loading it again? Basically I convert the mycalculator.lua into a string and then run it. I don't want to put mycalculator.lua file into the file system, I just want to hand it over as a string and then be able to require it in the next string I pass to the stack Thanks
There is a difference between simply executing a Lua script and loading a Lua module. If you wish to load a Lua module, then you must actually load a Lua module exactly as a script would: by calling require.
Since you appear to be new to Lua, I should probably explain this. You've probably seen code like this in Lua scripts:
require 'mycalculator'
That is not some special statement to Lua. That is a function call. It is just some syntactic sugar for:
require('mycalculator')
Functions in Lua can be called with NAME VALUE syntax instead of NAME(...) syntax, but it only allows you to send one parameter. And the parameter must be a literal (or table constructor).
In order to call the Lua require function from C, you must use the Lua stack. You must fetch the function from the global table by using lua_getfield(L, LUA_GLOBALSINDEX, "require"); Then, you push a string onto the stack containing the name of the module to load. Then, you use lua_pcall or whatever Lua function calling function to call it.