List concatenation

[Caligari]

Does Cobra have any operator to allow list concatenation?

I found some discussions on these forums that indicated why + is not concatenation for lists, and talked about using &. But I don't see any indication that the & functionality was ever added. Am I missing something? If not, is this still planned? It sure feels clumsy to use the .NET level functionality (and I think it gave me a lot of headaches with dynamic and ? versions of lists and list elements).

I can go back and work out the confusion I ran into trying to concatenate string lists, if it would be helpful.

- Caligari

[Charles]

We're sticking with + for concatenation and it currently works with strings.

.NET has .addRange, but it modifies the receiver and returns nothing, so it is not expression friendly. Other than that, it works fine.

In response to your inquiry, I whipped up the following extension method which is expression friendly:

extend IList<of T>

    def concated(other as IList<of T>?) as IList<of T>
        """
        Returns a new list with the contents of this list and the other.
        Does not modify this list or the other.
        The returned list is the same class as the receiver.
        Assumes the receiving type has an initializer that takes a .
        """
        type = .typeOf
        newList = type(.count + if(other,other.count,0))
        newList.addRange(this)
        if other, newList.addRange(other)
        return newList
        

class X

    def main is shared
        t = [1, 2]
        u = [3, 4]
        # print t + u  # not supported yet
        # print t.addRange(u)  # no good. addRange returns nothing
        trace t, u
        trace t.concated(u)

If we add + support for lists, what should it do if both sides are the nilable type (List<of T>?) and end up being nil at run-time?

[Caligari]

If both are nilable, and nil at runtime, shouldn't we return nil? We haven't got any actual data, so there isn't really anything else we can do, is there?

I'll grab the changes (assuming they are in the repository) and try my code with the new Cobra and let you know if there was anything else that still confuses me.

- Caligari

[Charles]

Sorry I didn't check in that extension yet. I wrote it fast and I'm tired. I'll take a fresh look at it this week.

Maybe you can copy it and test it out?

[Caligari]

Well, I've taken an initial stab at this, which has reminded me about one of the issues I encountered.

I've added the concated extension as above. My test is:

Code: Select all

class TestList

    def main is shared
        listArgs = ["-l", "-list"]
        ignoreArgs = ["-i", "-ignore"]
        nameArgs = ["-n", "-name", "-names"]
        summaryArgs = ["-s", "-summary"]
        helpArgs = ["-h", "-help"]

        allArgs = listArgs.concated(ignoreArgs.concated(nameArgs.concated(summaryArgs.concated(helpArgs))))

        print allArgs


And when I compile I get:

Code: Select all

TestList.cobra(23): error: Cannot find a definition for "concated" in "summaryArgs" whose type is "List<of String>".
TestList.cobra(23): error: Cannot find a definition for "concated" in "nameArgs" whose type is "List<of String>".
TestList.cobra(23): error: Cannot find a definition for "concated" in "ignoreArgs" whose type is "List<of String>".
TestList.cobra(23): error: Cannot find a definition for "concated" in "listArgs" whose type is "List<of String>".
Compilation failed - 4 errors, 0 warnings


So, I'm not sure why I've getting List<of ...> rather than IList<of ...>. This definitely confused me when I was first tangling with this, and I ended up with:

Code: Select all

class TestList

    def main is shared
        listArgs as List<of String?> = ["-l", "-list"]
        ignoreArgs as List<of String?> = ["-i", "-ignore"]
        nameArgs as List<of String?> = ["-n", "-name", "-names"]
        summaryArgs as List<of String?> = ["-s", "-summary"]
        helpArgs as List<of String?> = ["-h", "-help"]

        allArgs = List<of String?>()
        allArgs.addRange(listArgs)
        allArgs.addRange(ignoreArgs)
        allArgs.addRange(nameArgs)
        allArgs.addRange(summaryArgs)
        allArgs.addRange(helpArgs)


Which seems like a lot more "manual" setup than I expected I'd need to do in order to use lists of strings. Am I missing something here?

- Caligari

[Charles]

Well, I've taken an initial stab at this, which has reminded me about one of the issues I encountered.

I've added the concated extension as above. My test is:

Code: Select all

class TestList

    def main is shared
        listArgs = ["-l", "-list"]
        ignoreArgs = ["-i", "-ignore"]
        nameArgs = ["-n", "-name", "-names"]
        summaryArgs = ["-s", "-summary"]
        helpArgs = ["-h", "-help"]

        allArgs = listArgs.concated(ignoreArgs.concated(nameArgs.concated(summaryArgs.concated(helpArgs))))

        print allArgs


And when I compile I get:

Code: Select all

TestList.cobra(23): error: Cannot find a definition for "concated" in "summaryArgs" whose type is "List<of String>".
TestList.cobra(23): error: Cannot find a definition for "concated" in "nameArgs" whose type is "List<of String>".
TestList.cobra(23): error: Cannot find a definition for "concated" in "ignoreArgs" whose type is "List<of String>".
TestList.cobra(23): error: Cannot find a definition for "concated" in "listArgs" whose type is "List<of String>".
Compilation failed - 4 errors, 0 warnings


It works for me. No compilation errors or warnings.

What version of Cobra are you on?

Also, I was picturing that .concated would be used:

a.concated(b).concated(c).concated(d)

# analogous to:
a + b + c + d

[Caligari]

Ah. I've been running install-from-workspace.bat by clicking on it.

I run it from a command prompt now, and I find that

Code: Select all

==== Build new Cobra compiler

run: Snapshot\cobra.exe -compile -turbo -ert:yes -files:files-to-compile.text
   : CommandLine.cobra(501): error: Cannot find "CobraMain".
   : Compilation failed - 1 error, 0 warnings

** ERROR: Exit code from running SnapshotCobra: 1


Which I will go out on a limb and suggest might be the reason that things are not behaving quite as you'd expect.

I'll have a look. My main drive is I:, which I've patched in the past, but perhaps something has changed in there that I missed this time around.

- Caligari

[Caligari]

OK, commenting out that line (501 in CommandLine.cobra), I now run into this, which seems odd not to have caused trouble earlier:

Code: Select all

run: Snapshot\cobra.exe -compile -turbo -ert:yes -files:files-to-compile.text
   : i:\Cobra\cobra-workspace\Source\Utils.cobra(368): warning: "System.Reflection.Assembly.LoadWithPartialName(string)" is obsolete: "This method has been deprecated. Please use Assembly.Load() instead. http://go.microsoft.com/fwlink/?linkid=14202"
   : error: Program "i:\Cobra\cobra-workspace\Source\Utils.exe" does not contain a static "Main" method suitable for an entry point
   : Compilation failed - 1 error, 1 warning

** ERROR: Exit code from running SnapshotCobra: 1


From what I can tell, indeed Utils.cobra doesn't contain a Main of any sort, and hasn't been altered recently to remove it. So I'm not sure why this would only be a problem now.

- Caligari

[Charles]

Sorry, I broke this a couple of days ago when "cobra.cobra", which contains the .main, was extracted out of files-to-compile.text to put on the command line.

Although this problem is not in the last informal release, it affects people working straight out of subversion.

Now fixed. Update and try again.

[Charles]

Oh and if you have modified the installer, the install paths were extracted to be more towards the top in a var:

var installDirectories = [r'C:\Cobra', '/usr/local/cobra']

So if you want a different path, you'll want to review that.