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[<isaacdefrain AT gmail.com>]

Hello and good day,

I'm defining a programming language whose configuration has multiple cells
with multiplicity="*", some of which are nested in cells with
multiplicity="*"; e.g. something like

module MOD-SYNTAX
  syntax    Term ::= "Stop" | Bool | Int | String // the exact definition is
not important
  syntax  Terms ::= Term > Term "," Term [right]
endmodule

endmodule

module MOD
  configuration
  <T>
    <k> .K </k>
    <one>
      <alpha multiplicity="*"> .K </alpha>
    </one>
    <two>
      <beta multiplicity="*">
        <gamma>
          <delta multiplicity="*"> .K </delta>
        </gamma>
      </beta>
    </two>
  </T>

// a bunch of rules

endmodule

I want to define two kinds of functions: the first from Terms to DeltaCellBag;
the second from AlphaCellBag to Terms. So in the MOD module, I have something
like

  syntax AlphaCellBag
  syntax DeltaCellBag
  syntax DeltaCellBag ::= "fun1(" Terms ")" [function]
  syntax Terms ::= "fun2(" AlphaCellBag ")" [function]

  rule fun1( A:Term ) => <delta> A </delta>
  rule fun1( A:Term , B:Terms ) => <delta> A </delta> fun1(B)

  rule fun2( .AlphaCellBag ) => Stop
  rule fun2( <alpha> A:Term </alpha> ) => A
  rule fun2( <alpha> A:Term </alpha> B:AlphaCellBag ) => A , fun2(B)

But the compiler complains about the second rule for fun1 and the third rule
for fun2 (I'm using RV-K version 1.0-SNAPSHOT
Git revision: 1e310cd
Git branch: UNKNOWN
Build date: Thu Jan 31 03:38:17 EST 2019)

It's not clear to me why this is an error. Can someone help me understand why
this error occurs and whether there is a way to define such functions (without
errors)?

Thank you!