I would like to know what are best practises of using Eclipse Scala interpreter (Eclipse Scala IDE).
Let's say I have application with breakpoint in it. Is it possible to debug an application in such a way, that I can execute/evaluate expressions inside REPL at the specific breakpoint? If yes how can I achieve it?
Another thing that made me wonder is what's the difference between opening the interpreter as Run configuration or opening it trough Window -> Show view -> Scala interpreter.
Do you know any other uses cases of Eclipse Scala interpreter that are interesting to know about, like for example Ctrl+Shift+X to run selected expression?
Maybe it is an obvious advice, but in addition to merely starting REPL in Scala IDE you can run selected expression in it: just select the expression and press Ctrl+Shift+X (default hotkey).
Update
There is a comprehensive reference for Scala interpreter (thanks Mirco Dotta).
It is also worth to mention that in near future Scala interpreter is going to be enhanced significantly: integration with Scala debugger and implementation of a concept known as worksheet are on the way.
Related
I want to see the step by step execution of a fortran code.
I have the option of gdb but i want something more visual inside an editor, something like visual studio code, but faster so that I can execute it till a break point and then see the execution from that point onwards step-by-step.
Any recommendation apart from the traditional terminal gdb for the same purpose ?
There is a plugin for eclipse for fortran, based on CDT. It is called Photran and provides a graphical interface for gdb, in addition to other useful features like makefile support and generation and declaration lookup.
Is there a way to run my .fs file with either a breakpoint or a command like System.Diagnostics.Debugger.Launch() in it so that I can use FSI to examine values, apply functions to them, plot them, etc.?
I know this question has been asked before but I tried the answers and could not make them work. Clear instructions or a link to a write-up explaining the process would be of great help not only to myself, but also, I believe, to all beginners.
Unfortunately, you cannot hit a breakpoint and jump into FSI. The context of a running .NET program is quite different to that of an interactive FSI session and they are not compatible enough to just switch between one or the other. I can understand an expectation of this kind of debugging when coming from other dynamic/interpreted languages such as JavaScript, Python etc. It is a really powerful feature.
As you have already noted, you can use the VS immediate window but you need to use its C#-like syntax and respect its limitations. Also, since it's not F#, you need to understand the F# to .NET conversion in order to make full use of it.
If you use Paket for dependency management in your project you have another option: Add generate_load_scripts: true to your paket.dependencies. This will give you a file like .paket\load\net452\main.group.fsx, which you can load into FSI to get all of the dependencies for your project. However, you are still responsible for loading in your own source files and building up some state similar to what is found at your desired breakpoint.
To hit a break point, in visual studio or visual studio code, you just click to the left of the line number you want to set your breakpoint. This is very much a supported feature in .fs files.
Using Java big IDEs compile my code while it is written so that errors are detected before runtime.
Is that possible with Ruby too? Actually I code in a Text editor. Errors are detetected at runtime only.
Is that possible with Ruby too?
If by that you mean "compiling", then no. If you mean "edit-time error detection", then also no.
Smart IDEs, like RubyMine, can guess/detect some errors, but only simple cases. And they are often confused by ruby's dynamic nature. (can't find location for a method, even though it's defined within the project. Or the opposite, find too many false positives).
In ruby, you simply can't know what does a piece of code do without running it.
I've written a little library that uses implicits to add functionality that one only needs when using the REPL in Scala. Ruby has libraries like this - for things like pretty printing, firing up text editors (like the interactive_editor gem which invokes Vim from irb - see this post), debuggers and the like. The library I am trying to write adds some methods to java.lang.Class and java.lang.reflect classes using the 'pimp my library' implicit conversion process to help you go and find documentation (initially, with Google, then later possibly with a JavaDoc/ScalaDoc viewer, and maybe the StackOverflow API eventually!). It's an itch-scratching library: I spend so much time copying and pasting classnames into Google that I figured I may as well automate the process.
It is the sort of functionality that developers will want to add to their system for use only in the REPL - they shouldn't really be adding it to projects (partly because it may not be something that their fellow developers want, but also because if you are doing some exploratory development, it may be with just a Scala REPL that's not being invoked by an IDE or build tool).
In my case, I want to include a few classes and set up some implicits - include a .jar on the CLASSPATH and import it, basically.
In Ruby, this is the sort of thing that you'd add to your .irbrc file. Other REPLs have similar ways of setting options and importing libraries.
Is there a similar file or way of doing this for the Scala REPL?
On the command line, you can use the -i option to load a file while starting the REPL:
scala -cp mystuff.jar -i mydefs.scala
Ofcourse you could wrap this in a shell script or batch file and run that instead of the normal scala command.
(I'm using Scala 2.8.0 RC3).
Not sure if this is what you are looking for, but if you put any jars in your SCALA_HOME\lib directory. Then those jars will be available for import in the REPL (using the import keyword).
EDIT: The most convenient option as of now is by setting the CLASSPATH environment variable. Any jars referenced in the CLASSPATH variable are also available for import in the REPL.
Quick answer probably not what you are looking for, but what about typing
:load path/to/some/scala/script/file.scala
in the console?
:load will read in a scala file and execute it as a script.
Another option is to use sbt set up your dependencies and execute the console command.
The final option I can think of is to set the classpath on the command line manually and point it to the jars / class file folders that you want the jvm to know about.
Let me know if any of this interests you and I can provide more details if needed.
We have a proprietry system that we develop scripting code in.
We currently do not have a developer environment (apart from Notepad++) and cannot debug or compile this code. We have to submit it to the vendor to insert the code into the test or live system.
The language is essentially C like and has the same syntax.
Basically we want a tool to be able to simply check the syntax of chunks of code we send to the vendor.
Does a tool exist that will do this for me?
You write code in a proprietary scripting language, so you require syntax checking because you cannot compile or debug the code onsite? I'd suggest getting a copy of the language reference (including the BNF if possible) from your vendor, get a compiler-compiler like Coco/R (http://www.ssw.uni-linz.ac.at/coco/), and build yourself a quick and dirty compiler that just validates the abstract syntax tree.
That is to say, yes, there are tools you can use, though perhaps they involve more work than what you may have hoped.
If it's really the same syntax as C you can use a C compiler. Usually there's a syntax check only option (/Zs for MSVC).
I'm not sure how many problems you'll run into since C compilers are pretty picky, and being "like C" is not the same as being C.
It does seem odd that you're being asked to develop code without having any capability to run or even compile it. Kind of like writing a book without being able to proof read it before publishing. I have a hard time getting even "Hello World" programs to compile & run without some sort of goof-up on the very first go.