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finos / morphir-elm

Tools to work with the Morphir IR in Elm.
https://package.elm-lang.org/packages/finos/morphir-elm/latest
Apache License 2.0
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Morphir-Elm Interpreter fails with first-class or partially applied functions #1139

Open edwardpeters opened 9 months ago

edwardpeters commented 9 months ago

Describe the bug The morphir-elm based interpreter frequently fails to work with first class or higher order functions; in particular, it reliably fails whenever a first class function relies on anything from lexical scope.

To Reproduce The following code works in native elm:

type MyEnum = TwoArg Int Int

unable_to_compute : Int -> MyEnum
unable_to_compute x = 
    let 
        inner = 
            let y = 5 in \z -> TwoArg y z
    in
        inner x

wrong_result : Int -> MyEnum
wrong_result x = 
    let 
        inner = TwoArg 5
    in
        inner x

In the morphir-elm interpreter, "unable_to_compute", as the name would imply, is unable to be computed. "wrong result" meanwhile ignores its input argument and results in "TwoArg 5".

Expected behavior I would expect the behavior to match elm, with first-class functions maintaining locally scoped variables.

Desktop (please complete the following information):

Additional context This may be relevant to the morphir-scala discussion on RTValue, MDM and IR at https://github.com/finos/morphir-scala/discussions/529