I'm running Scala 2.10 program through sbt run from Windows 7 command line and I see an unexpected behavior while calling readLine overload with the prompt. The prompt is shown after the actual line input.
Source
object MyExample extends App {
readLine("This prompt is shown after the readline!")
}
build.sbt
name := "hello"\n
\n
version := "1.0"\n
\n
Output
asdf
This prompt is shown after the readline!
Is there something I don't understand or is it a bug? It seems to be working as expected from IDEA.
Sbt version: 0.13.1
I've run into this before with giter8. The work around is to do your own print, flush the output stream, and then read. See this pull request for an example of the workaround.
Someone has fixed it in the scala source about a month ago. I don't have any idea when we will see that fix, tho.
Related
I am trying to run scala program in cmd prompt. And I get the message.
"No, such file or class on class path exists."
Things that may be relevant:
I had several warnings from Windows about downloading and running the scala executable from the site. (I ignored them all )
I had to enter a Admin Command Line to use scala, and it did not show up in my program files after install.
The installer never actually popped up for me. So I ran the executable as administration, now
it appears in my program X86 folder. and I can enter scala mode without being in Admin mode. 4. The .scala file does compile. with scalac hello.scala
The code given to me by my instructor, in a file I named hello.scala object hello extends App{ println("Hello") }
Finally, I have looked at 2 Youtube videos and 2 Stack posts before asking this question. Thank you all for your time.
Here's a complete transcript of a successful session compiling and running on this code:
% echo 'object hello extends App{ println("Hello") }' > hello.scala
% scalac hello.scala
% scala hello
Hello
Are you doing something different? If so, what is it? Show a transcript of your entire effort, including all commands you entered and all error messages you got.
I successfully installed coq 8.9.1 and coq-quickchick 1.1.0 with opam 2.0.4 and I'm programming on emacs 26.1.
However, when running a QuickChick command I received the following error:
Error: Could not compile mli file
Any ideas of what I can do?
Also, I have tried to include the following command before the QuickChick command:
"QuickChickDebug Debug On."
Still, no success and no instructive message was provided.
You can try to manually extract and compile.
A first idea is to replace QuickChick my_prop. with Extraction TestCompile my_prop., which will also try to compile.
There is also Separate Extraction my_prop. (assuming my_prop is an identifier), which just outputs .ml files so you can compile them by hand and see what is wrong.
There are other variants of extraction worth knowing about:
https://coq.inria.fr/distrib/current/refman/addendum/extraction.html#generating-ml-code
Can you compile the file from command line? If you can, you can open emacs from the command line and re-run and see.
BTW, what's your OS? I have the same problem on OS X Catalina and the problem comes from the privacy policy of Catalina I guess.
I've recently installed Scala as a part of my functional programming course and I've encountered a problem: IntelliJ IDEA 2017.2.1 (Java version 9, build 9+181) doesn't run any of my scala code, exitting with
Error: Could not find or load main class Main
This code is an example.
object Main {
def length[A](list:List[A]):Int = {
if (list == Nil) 0
else 1 + length(list.tail)
}
def main(args: Array[String]): Unit = {
length(List[Int](1, 4, 5, 12, -1))
}
}
It's really simple, yet IntelliJ refuses to run it. Windows CMD doesn't even react to a scala command, resulting into
'scala' is not recognized as an internal or external command,
operable program or batch file.
even though I have it installed on my computer. If I call Scala Console inside of IntelliJ everything works fine and compiles as expected. I've tried switching to JDK 1.8 inside of IntelliJ, yet it led to no result.
What could be the problem?
For me it turns out that the src/main was not marked as Sources Root
which causes the following error
...
One of the two will be used. Which one is undefined.
Error: Could not find or load main class Main
Process finished with exit code 1
So of course after I mark the src/main as Sources Root, the Scala Hello World example runs happy again.
Notice the blue color of directory src/main when it's marked as Sources Root
Are you using the little green arrow to run the program from inside of your Main object?
How did you create the program? It could be that your build file SBT configuration of the project is a different Scala version than what's installed on your computer.
It's really simple, yet IntelliJ refuses to run it. Windows CMD
doesn't even react to a scala command, resulting into
'scala' is not recognized as an internal or external command, operable program or batch file.
This means that Scala is not added to your class path in your terminal. Look up how to do that and see if that doesn't help out your IntelliJ problem too.
When using sbt console I find myself repeatedly entering some import statements. It would be great if there was a way to tell sbt to always run commands. Is there a way?
At the moment I have a kinda crufty solution:
( echo "import my.app._
import my.app.is.sooo.cool._" && cat ) | sbt console
Googleability words:
Initial commands, first commands, initial expressions, build file, initial statements, startup expressions, startup commands, startup statements.
You can use initialCommands:
initialCommands in console := """import my.app._
import my.app.is.sooo.cool._"""
Given that "sbt console" lets you run the scala repl, why not just create a custom .scala file (say "default.scala") where to store all the imports, and then just run :load /path/to/default.scala? This would achieve what you need in a persistent way.
If I run the below script (saved as jarAccessTest.sh, which is an executable file) in a command line, nothing happens:
#!/bin/sh
# exec scala -classpath "/usr/local/google/home/vvasuki/sanskritnlpjava/target/sanskritnlp-1.0-SNAPSHOT.jar " "$0" "$#"
exec scala "$0" "$#"
!#
# import sanskritnlp.transliteration._;
print "hello"
I just see no output. Nothing. Command prompt does not return either.
What is happening here? I have to type Ctrl+C to stop whatever is happening.
EDIT: Using scala 2.9 in ubuntu 14.04 : http://i.imgur.com/VMYKnUX.png
Your pre-packaged version of Scala is from a long time ago and a galaxy far, far away.
You'll do better to download the latest 2.11.6 from the website.
When the scala runner runs a script, it starts a compile server process. If that process is borked, you may have to kill it or run fsc -shutdown to ask it nicely to go away.
You can try adding the -nc option to your script to eliminate that factor, i.e., scala -nc says no compile daemon.
Finally, if you're just testing your library, it's more common to run scala -cp my.jar and experiment from the REPL. Or if you are using SBT, start the console from there.
Anonymous suggests adding: "They seriously let you type anything on here"
To which I'll append the advice from the other answer, to run fsc -verbose. And note that they threaten to stop supporting fsc because it has issues which are maddening when they occur. For that reason, I prefer scala -nc for brief testing and scalac -d script.jar script.scala where script is an App.
The problem on the original computer was never really explained, though it is pointed out that use of the '-nc' flag worked.
The original problem might with the compilation daemon's ability to open a port. From the man page for fsc:
The first time it is executed, the daemon is started automatically.
On subsequent runs, the same daemon can be reused, thus resulting in a faster compilation. The tool is especially effective when repeatedly
compiling with the same class paths, because the
compilation daemon can reuse a compiler instance.
One way to check if this is the problem is to run fsc on its own with the verbose flag. For example, make a script called hello.scala with
println("Hello")
in it, and run
fsc -verbose hello.scala
If this shows the compile server unable to connect, you've identified your problem. A first thing to try in that case would be to check that your hosts file is kosher.
(I had a similar problem, and this is what I found).
you have a few changes to do on your code, mainly on the # line which is not a comment in scala.
#!/bin/sh
# exec scala -classpath "/usr/local/google/home/vvasuki/sanskritnlpjava/target/sanskritnlp-1.0- SNAPSHOT.jar " "$0" "$#"
exec scala "$0" "$#"
!#
// import sanskritnlp.transliteration._;
print ("hello\n")