Is there a way to use records directly in erl? No matter what I try, it always says it canno find the record. I am trying to do mnesia transactions and I cannot go too far without my records. Any help is greatly appreciated - thank you!
Yes, use help() and find these commands in the shell.
rd(R,D) -- define a record
rf() -- remove all record information
rf(R) -- remove record information about R
rl() -- display all record information
rl(R) -- display record information about R
rp(Term) -- display Term using the shell's record information
rr(File) -- read record information from File (wildcards allowed)
rr(F,R) -- read selected record information from file(s)
rr(F,R,O) -- read selected record information with options
These are a clever hack in the shell, they allow you to load record definitions used in modules when they were compiled. Use the rr command to load it from your module.
Remember that these are only available for the interactive shell to use.
How do you mean? In the shell, then it is as Christian wrote. If you mean in a module then you still have to define records before you can use them. See the erlang docs, online at http://erlang.org/doc/, for a description on how to do this. They are only a compile time construction, so they don't exist as such.
Related
my question is quite the same as this one :
How to Iterate over target objects of outgoing links in DXL, in Modules not previously loaded
but regarding incoming links.
I would like to use the source objects of incoming links but there are located in module that are not previsously loaded.
I don't want to open and close module each time because it would cost too much time. I would like to open them once and close them at the end.
Two solution for this :
be able to know if the module is already open or not so that I don't open it again (is there a "is_open" function in DXL + store the list of open module in a table and close them all at the end.
or better :
before start of loop, use a loop using the link module and the target module to find all module in the database that could be linked to the target module. And I load them all (even if there is no links between them. But my script would be simpler this way). How can I do this ? I tried something like :
ModName_ src_mod_linkset
for src_mod_linkset in "target_module"<-"linkmodulename" do
{
print "test"
}
but in this kind of loop, it doesn't work because "target_module" should be an object and not the complete module.
https://www.ibm.com/mysupport/s/forumshome has a lot of information on this. A query "Engineering Requirements Management DOORS" incoming links brings you some example scripts. I prefer this approach (load the ModuleVersion if its data is null): https://www.ibm.com/mysupport/s/forumsquestion?language=de&id=0D50z00006HIDztCAH
About "is_open": there is a loop for module in database, which gives you a list of all open modules. You might want to store all open modules at the star of your script in a Skip list and when iterating over the incoming modules check to see whether you have to close the module at the end of your script.
I would not use your second approach if you plan to run your script on baselines, it might happen that the link set in the link module has been deleted in the meantime, so you will not get all possible in links. Anyway, the link modules could be anywhere in your database, not necessarily near your incoming module.
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.
We're trying to make a DTS package where it'll launch a stored procedure and capture the contents in a flat file. This will have to run every night, and the new file should overwrite the existing file.
This wouldn't normally be a problem, as we just plug in the query and it runs, but this time everything was complicated enough that we chose to approach it with a stored procedure employing temporary tables. How can I go about using this in a DTS package? I tried going the normal route with the Wizard and then plugging in EXEC BlahBlah.dbo... It did not care for that:
The Statement could not be parsed. Additional information: Invalid object name '#DestinyDistHS'. (Microsoft SQL Server Native Client 10.0)
Can anyone guide me in the right direction here?
Thanks.
Is it an option to simply populate a non-temp table in your SP, call it and select from the non temp table when exporting?
This is only an issue if you have multiple simultaneous calls to the stored procedure. In this case you can't save to a single table.
If you do have multiple simultaneous calls then you might be able to:
Create a temp table to hold results
Use INSERT INTO #TempTable EXEC YourProc
SELECT FROM #TempTable
You might need to do this in a more forgiving command line tool (like SQLCMD). It's not as fussy about metadata.
I follow the REST API with yaws tutorial of the 'Building web application with Erlang' book.
I get the following error when starting $ yaws :
file:path_eval([".","/Users/<uername>"],".erlang"): error on line 3: 3: evaluation failed with reason error:{undefined_record,airport} and stacktrace [{erl_eval,exprs,2,[]}]
.erlang file:
application:start(mnesia).
mnesia:create_table(airport,[{attributes, record_info(fields, airport)}, {index, [country]}]).
rest.erl file can be found here.
How can I define a record? I tried to add rd(airport, {code, city, country, name}). without success.
Record 'airport' is defined in the module rest, and all functions in the 'rest' know about record 'airport'. But when you start your application, erlang executes .erlang file, which has nothing to do with the module rest. So, erlang just has no idea what is the record airport and where to find it.
Easiest workaround I believe - is to define some function (for instance 'init') in the module rest, this function must contain all that you have now in .erlang file, export it, and in the .erlang file just invoke rest:init().
I'm using a closed-source application that loads Lua scripts and allows some customization through modifying these scripts. Unfortunately that application is not very good at generating useful log output (all I get is 'script failed') if something goes wrong in one of the Lua scripts.
I realize that dynamic languages are pretty much resistant to static code analysis in the way C++ code can be analyzed for example.
I was hoping though, there would be a tool that runs through a Lua script and e.g. warns about variables that have not been defined in the context of a particular script.
Essentially what I'm looking for is a tool that for a script:
local a
print b
would output:
warning: script.lua(1): local 'a' is not used'
warning: script.lua(2): 'b' may not be defined'
It can only really be warnings for most things but that would still be useful! Does such a tool exist? Or maybe a Lua IDE with a feature like that build in?
Thanks, Chris
Automated static code analysis for Lua is not an easy task in general. However, for a limited set of practical problems it is quite doable.
Quick googling for "lua lint" yields these two tools: lua-checker and Lua lint.
You may want to roll your own tool for your specific needs however.
Metalua is one of the most powerful tools for static Lua code analysis. For example, please see metalint, the tool for global variable usage analysis.
Please do not hesitate to post your question on Metalua mailing list. People there are usually very helpful.
There is also lua-inspect, which is based on metalua that was already mentioned. I've integrated it into ZeroBrane Studio IDE, which generates an output very similar to what you'd expect. See this SO answer for details: https://stackoverflow.com/a/11789348/1442917.
For checking globals, see this lua-l posting. Checking locals is harder.
You need to find a parser for lua (should be available as open source) and use it to parse the script into a proper AST tree. Use that tree and a simple variable visibility tracker to find out when a variable is or isn't defined.
Usually the scoping rules are simple:
start with the top AST node and an empty scope
item look at the child statements for that node. Every variable declaration should be added in the current scope.
if a new scope is starting (for example via a { operator) create a new variable scope inheriting the variables in the current scope).
when a scope is ending (for example via } ) remove the current child variable scope and return to the parent.
Iterate carefully.
This will provide you with what variables are visible where inside the AST. You can use this information and if you also inspect the expressions AST nodes (read/write of variables) you can find out your information.
I just started using luacheck and it is excellent!
The first release was from 2015.