Cobra Forums

Posted: **Wed Jan 01, 2014 11:50 pm**

Hi Charles, Are you ready for another round? ;-)

well, I am actually coding, and using the MonoDevelop addin.
Today I ran into this COBRA INTERNAL ERROR

I can send you the entire project, it's a small application that I hope will reach fruition. It's purpose is to suggest a garden arrangement based on companion planting. I'm in the 0.1 stages, but it's coming along nicely. Anyway I'm enjoying using cobra with the concise syntax, and learning new features all the time (why is the documentation hidden? ;-)

)

so back from the excursion, here is the output from MonoDevelop xbuild.

Code: Select all: Building: SimpleGardenPlanner (Debug) Build started 1/2/2014 8:41:58 AM. __________________________________________________ Project "/home/kobi/WualaDrive/temperate/work_backup/SimpleGardenPlanner/SimpleGardenPlanner.cobraproj" (Build target(s)): Target PrepareForBuild: Configuration: Debug Platform: AnyCPU Target GenerateSatelliteAssemblies: No input files were specified for target GenerateSatelliteAssemblies, skipping. Target CoreCompile: Tool /usr/local/bin/cobra execution started with arguments: -compile -back-end:none -clr-platform:AnyCPU -copy-core:no -correct-source:none -debug:1 -delay-sign:no -embed-run-time:yes -include-traces:yes -keep-intermediate-files:no -native-compiler:auto -number:decimal -out:/home/kobi/WualaDrive/temperate/work_backup/SimpleGardenPlanner/obj/Debug/SimpleGardenPlanner.dll -target:lib -contracts:inline -include-asserts:yes -include-nil-checks:yes -include-tests:yes -optimize:no -reference:/home/kobi/WualaDrive/temperate/work_backup/Json.NET/Bin/Net40/Newtonsoft.Json.dll -native-compiler-arg:"/errorreport:none" /home/kobi/WualaDrive/temperate/work_backup/SimpleGardenPlanner/Code/Dirt.cobra /home/kobi/WualaDrive/temperate/work_backup/SimpleGardenPlanner/Code/Garden.cobra /home/kobi/WualaDrive/temperate/work_backup/SimpleGardenPlanner/Code/IFieldItem.cobra /home/kobi/WualaDrive/temperate/work_backup/SimpleGardenPlanner/Code/Plant.cobra /home/kobi/WualaDrive/temperate/work_backup/SimpleGardenPlanner/Code/ManageGarden.cobra /home/kobi/WualaDrive/temperate/work_backup/SimpleGardenPlanner/Code/Stone.cobra /home/kobi/WualaDrive/temperate/work_backup/SimpleGardenPlanner/Code/Utils.cobra /usr/lib/mono/xbuild/Cobra/Cobra.targets: error : error: COBRA INTERNAL ERROR / NullReferenceException / Object reference not set to an instance of an object Task "CobraCompiler" execution -- FAILED Done building target "CoreCompile" in project "/home/kobi/WualaDrive/temperate/work_backup/SimpleGardenPlanner/SimpleGardenPlanner.cobraproj".-- FAILED Done building project "/home/kobi/WualaDrive/temperate/work_backup/SimpleGardenPlanner/SimpleGardenPlanner.cobraproj".-- FAILED Build FAILED. Errors: /home/kobi/WualaDrive/temperate/work_backup/SimpleGardenPlanner/SimpleGardenPlanner.cobraproj (Build) -> /usr/lib/mono/xbuild/Cobra/Cobra.targets (CoreCompile target) -> /usr/lib/mono/xbuild/Cobra/Cobra.targets: error : error: COBRA INTERNAL ERROR / NullReferenceException / Object reference not set to an instance of an object 0 Warning(s) ---------------------- Done ---------------------- Build: 1 error, 0 warnings

Posted: **Thu Jan 02, 2014 2:38 am**

The documentation is all over the wiki. And community editable.

This is your offending line:

# Garden.cobra
var _plantSchema = JsonSchema.parse(Plant.plant_schema)

Specifically when Cobra tries to process "Plant.plant_schema", which is a shared method, it's not ready to do so yet. You should be able to work around with something like:

var _plantSchema as JsonSchema?
    ...
    # inside a property or method:
    _plantSchema ?= JsonSchema.parse(Plant.plant_schema)

...while I work on making this work or at least providing a good error message.

Posted: **Thu Jan 02, 2014 2:53 am**

Well actually you could just put the initialization in cue.init:

class Garden

    cue init...
        base.init
        _plantSchema = JsonSchema.parse(Plant.plant_schema)

Posted: **Thu Jan 02, 2014 10:46 pm**

This is fixed now in two ways:

1) You will get a proper error message:

Code: Select all: error: Cannot compile initialization expression at this point. Add an explicit type to the `var` ("as <type>") or move to a `cue init` or change the expression.

2) If you explicitly type the variable (by adding "as String", "as JsonSchema", etc) then it will work (as indicated in the new error message). This was not previously the case.

Posted: **Sat Jan 04, 2014 11:34 pm**

hi Charles
my original intention with submitting the error reports about 'internal errors' was just to find where I typed something wrong, having the compiler state at least the line number where it balked. Then it would help find the problem on my own.
of course your fix is much better.

With regard to this use case, what I meant to do
is have a constant (or readonly) static variable that got its value just once, but during runtime.
something like

Code: Select all: private static decimal PI = getPiValueFromFile(@"/home/huge_pi.txt")

(what is the fixation some people have with pi is beyond me)

Posted: **Sun Jan 05, 2014 12:08 pm**

IIRC your var was not shared/static. The equiv Cobra would be something like:

class A

    shared

        var pi = .readNumberFromFileNamed('/home/huge_pi.txt')

        def readNumberFromFileNamed(fileName as String) as number
            return decimal.parse(File.readAllText(fileName))

...hmm I don't think we have a "number.parse" but using `number` still reduces the number of places you would have to edit if you went with "@number float64" at some point.

Posted: **Mon Jan 06, 2014 4:28 am**

is it possible to do something like this?
notice the "is shared" after var is initialized.
is it possible to write it as one line?

class A

    shared
        def readNumberFromFileNamed(fileName as String) as number
            return decimal.parse(File.readAllText(fileName))

    var pi = .readNumberFromFileNamed('/home/huge_pi.txt') is shared

Posted: **Mon Jan 06, 2014 4:36 am**

Unfortunately, "is" is overloaded, which was a mistake on my part:
1) an operator for reference comparisons. `a is b` in Cobra means `a` and `b` refer to the same object (pointer equality)
2) a part of the syntax for declaring modifiers. `... is shared`

Community member Hopscc would like to resolve this in initialization expressions by preferring that the `is` be interpreted as 2. So far, I have resisted because at that point in the code you are in an expression.

Posted: **Tue Jan 07, 2014 2:23 am**

Actually no - tho that was the first approach.

The problem is that theres an ambiguity in the syntax with declaration with an initialisation expression (clause) and the isnames clause with the current ordering of the two of them.
The most recent patch/approach for this ( from ..ahem.. 4 years ago) changes the clause ordering and the ambiguity/problem goes away
( and it doesnt even cause any problems...)

from memory the order change is along the lines that kobi7 is asking about

(Its all detailed on ticket:34)

evidently the combination of an initialisation clause and isnames clause is rather uncommon...

Posted: **Tue Jan 07, 2014 7:57 am**

hopscc wrote:evidently the combination of an initialisation clause and isnames clause is rather uncommon...

I think only because it doesn't work. I know I've tried it, saw it didn't work and then just moved on to a different approach.

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