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[Rikard Hjort <benparad AT hotmail.com>]

What is the compiler saying? What's the output?

On 10/17/19 10:50 PM, 
isaacdefrain AT gmail.com
 wrote:
> Hello and good day,
>
> I asked before, but did not get a response so I'm trying again :-)
>
> I'm defining a programming language whose configuration has multiple cells
> with multiplicity="*", some of which are nested in cells also with
> multiplicity="*"; e.g. something like
>
> module MOD-SYNTAX
>   syntax    Term ::= "Stop" | Bool | Int | String | "[" Terms "]" // the 
> exact
> definition is
> not important
>   syntax  Terms ::= Term > Term "," Term [right]
> endmodule
>
> endmodule
>
> module MOD
>   configuration
>   <T>
>     <k> $PGM:Term </k>
>     <one>
>       <alpha multiplicity="*"> .K </alpha>
>     </one>
>     <two>
>       <beta multiplicity="*">
>         <gamma>
>           <delta multiplicity="*"> .K </delta>
>         </gamma>
>       </beta>
>     </two>
>   </T>
>
> // a bunch of semantic rules
> endmodule
>
> I'd like 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!