Re: [fricas-devel] Re: Programming with BTREEs.

Martin Rubey <[email protected]> writes:

> Dear Ralf,
> 
> I'm extremely grateful that you answered...
> 
> Ralf Hemmecke <[email protected]> writes:
> N := Union(Symbol, List Integer)
> BT := BinaryTree N
> B ==> binaryTree  -- the 3-argument version
> V ==> binaryTree  -- the 1-argument version
> bt:BT:=B(V e,[5,1],B(B(V a,[1,1],V b),[1,1],B(V c,[1,2],V d)))
> 
> [...]
> 
> S==>Symbol
> L==>List Integer
> construct(x: S, l: L, y: S): BT == binaryTree(V(x::N), l::N, V(y::N))
> bt2: BT := [e,[5,1],[[a,[1,1],b],[1,1],[c,[1,2],d]]]
> 
> ['a, [1,3], 'b]@BT
> 
> works for me
> 
> but 
> 
> [e,[5,1],[[a,[1,1],b],[1,1],[c,[1,2],d]]]@BT
> 
> cannot work, I think, because the argument types don't match.  You
> will need to allow also binary trees.

construct(x: Union(S, BT), l: L, y: Union(S, BT)): BT == binaryTree((if x case S then V(x::N) else x::BT), l::N, (if y case S then V(y::N) else y::BT))

will work *almost*:

(20) -> ['a, [1,3], ['d, [1,3], 'c]@BT]@BT

   (20)  [a,[1,3],[d,[1,3],c]]
                                Type:
                                BinaryTree(Union(Symbol,List(Integer)))

(21) -> ['a, [1,3], ['d, [1,3], 'c]]@BT
   Conversion failed in the compiled user function construct .
 
   Cannot convert from type List(Any) to Union(Symbol,BinaryTree(Union(
      Symbol,List(Integer)))) for value
   [d,[1,3],c]


Not sure whether this is an improvement.

Martin