Omitted array coding

[arisawa]

Is there such a form of the C# in Cobra?

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string[] array;
array = new string[] {"A", "B", "C"};


[agustech]

you can use:

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strarray = ["A","B","C"].toArray


[arisawa]

I see.
Thank you

[Charles]

strarray = @['A', 'B', 'C']

# so the general form is:

@[ ... ]

In other words, like a list, but starting with an @. This is a syntax I copied from Powershell.

An array-based syntax became important because there are several methods in the .NET standard library that take an array of some type as opposed to a List<of>. .NET < 2.0 did not have generics.

Using .toArray is okay, but the @[...] is more direct and efficient.

[agustech]

Would it be possible to extend String to overload:

String().split()
String.join()

so they can use List<> instead of array?

In case that you think it is a good idea and makes sense, could you give me some tips so I can integrate it in Cobra.Lang?

[Charles]

Yes, I think this is a good idea. Unfortunately, Cobra does not yet handle the combination of extensions and member overloads. For example, the following code fails to compile:

extend String

    def split(chars as IList<of char>) as String[]
        return String[](5) # TODO
        

class X

    def main is shared
        s = 'a,b:c:d,e,f'
        trace s.split([c',', c':'])

However, it does get all the way to code generation so maybe this is a reasonably small bug. I have augmented ticket:1 with some notes.

You can tell extensions were high on my mind since I entered them as the first Trac ticket.

Regarding augmenting Cobra.Lang, the files are now found in a subdir of Source called Cobra.Lang so that's:

<workspace>\Source\Cobra.Lang\*.cobra

You'll notice one of the files is called "Extensions.cobra". Also, if you were to add a file, you would add its filename to the "files.text" file in that same directory.

Then to rebuild the Cobra.Lang.dll in the Source directory, you say "cobra -bsl" or "cobra -bsl -v:2" if you want something more interesting to look at it.

Or you can say "install-from-workspace" if you're ready for that.

Finally, when creating library code, strongly consider using interfaces like IList<of> for argument types so that the method can be reused with more types of objects.

[Charles]

strarray = @['A', 'B', 'C']

# so the general form is:

@[ ... ]

In other words, like a list, but starting with an @. This is a syntax I copied from Powershell.

An array-based syntax became important because there are several methods in the .NET standard library that take an array of some type as opposed to a List<of>. .NET < 2.0 did not have generics.

Using .toArray is okay, but the @[...] is more direct and efficient.

I forgot to mention that you can allocate a blank array like so:

nums = number[](100)

# the very general format is
<var-name> = <type>(<args>)
# and in the case of arrays, the type is an array type (suffixed by "[]")
# and the arg is the length of the array,
# so the array allocation form is:
<var-name> = <type>[](<length>)

# another example
n = 1024
ch = char[](n)
for i in n, ch[i] = c'z'

[Charles]

Would it be possible to extend String to overload:

String().split()
String.join()

so they can use List<> instead of array?

In case that you think it is a good idea and makes sense, could you give me some tips so I can integrate it in Cobra.Lang?

I fixed the problem that was preventing this. I also added the extensions for split() to Cobra.Lang\Extensions.cobra. You can pass in any IList<of char>. The return value is a List<of String>.

Try it out.

[agustech]

It works, but ...

I have been trying to implementing some other methods and I have found the following issues (sorry if they are stupid ones):

1. This gives errors on the "Clean up workspace" phase but it works ok when I try to use it (I guess that there are better/more efficient ways to do it, it is just a test).

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      def split(ch as char) as List<of String>
         test
            s = 'a,b,c,d,e,f'
            assert s.split(c',') == ['a', 'b', 'c', 'd', 'e', 'f']
         body
            return List<of String>(.split(@[ch]))


2. I can not use list[:-1] inside Extensions.cobra while it works perfectly on my programs. I guess it is because that idiom is defined somewhere later.

3. overloaded shared methods compile correctly but they can not be used on programs, i.e. this compiles inside Extensions.cobra:

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      def join(j as String, li as IList<of String>) as String is shared
         test
            #li = ['a','b','c','d','e']
            #assert String.join(',',li) == "a,b,c,d,e" # error, can not test it while adding it?
            pass
         body
            str = ""
            if li.count == 0, return str
            #for s in li[:-1] #fails to compile if in library, if standalone program it works ok
            for n in li.count
               if n > (li.count - 2),  break
               str += li[n] + j
            str += li[li.count - 1]
            return str


but gives ' "String" is type' error when trying to use it:

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   assert String.join(',',['a','b','c','d','e']) == 'a,b,c,d,e' # error compiling


am I doing something wrong?

[Charles]

1. I fixed the problem with the "Clean up workspace" phase of the installer. It was forgetting to use the "-ert:yes" flag that you see in comp.bat (or comp on *nix).

2. The problem with list[:-1] is almost certainly a bug, but I'm unable to reproduce it. I would love to get the exact code for this.

3. Interesting. C# has only instance-oriented extension methods and I followed their lead doing the same thing with Cobra. I never even tried a shared one. But I can't think of any reason not to support shared. Can anyone?