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SeanTAllen/oa.pony

Created May 18, 2016 17:01
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  1. SeanTAllen created this gist May 18, 2016.
    66 changes: 66 additions & 0 deletions oa.pony
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,66 @@
    interface ExpAlg[E]
    fun lit(x: I32): E
    fun add(e1: E, e2: E): E

    interface Eval
    fun eval(): I32

    interface EvalExpAlg
    fun lit(x: I32): Eval val =>
    recover
    object
    let x: I32 = x
    fun eval(): I32 => x
    end
    end

    fun add(e1: Eval val, e2: Eval val): Eval val =>
    recover
    object
    let e1: Eval val = e1
    let e2: Eval val = e2
    fun eval(): I32 => e1.eval() + e2.eval()
    end
    end

    interface SubExpAlg[E] is ExpAlg[E]
    fun sub(e1: E, e2: E): E

    interface EvalSubExpAlg
    fun sub(e1: Eval val, e2: Eval val): Eval val =>
    recover
    object
    let e1: Eval val = e1
    let e2: Eval val = e2
    fun eval(): I32 => e1.eval() - e2.eval()
    end
    end

    interface PPrint
    fun print(): String

    interface PrintExpAlg2
    fun lit(x: I32): String =>
    x.string()

    fun add(e1: String, e2: String): String =>
    e1 + " + " + e2

    fun sub(e1: String, e2: String): String =>
    e1 + " - " + e2

    actor Main
    new create(env: Env) =>
    let ea = object is EvalExpAlg end
    let esa = object is (EvalSubExpAlg & EvalExpAlg) end
    let pa2 = object is PrintExpAlg2 end

    let ev = exp1[Eval val](esa)

    env.out.print("PRINTING\n" + exp1[String](pa2) + "\n" + exp2[String](pa2))

    fun exp1[E: Any #read](alg: ExpAlg[E] box): E =>
    alg.add(alg.lit(3), alg.lit(4))

    fun exp2[E: Any #read](alg: SubExpAlg[E] box): E =>
    alg.sub(exp1[E](alg), alg.lit(4))