Fix pat->Condition[...] apply rules

[mmatera]

This PR fixed the bug described in #619 regarding the result of applying this kind of rule. The problem was not in the apply method itself but in the do_replace method.

[rocky]

I just tried this on galatea and I don't see these results. Here is what I see:

>> f[x]/.(f[u_]->u^2/; u>3/; u>2)
 = x ^ 2 /; x > 3 /; x > 2
>> f[1.]/.(f[u_]->u^2/; u>3/; u>2)
 = 1. /; 1. > 3 /; 1. > 2

[mmatera]

You are right. When I tested it, I did it with delayed rules instead. There is something that I still am missing.

[mmatera]

This property helps to distinguish if the Rule comes from a Rule expression or a RuleDelayed expression, and it is needed to handle the different behavior observed in WMA. I do not see a reason for this different behavior, but maybe it is, and maybe there is a different behavior in other contexts.

[mmatera]

Still, there is something that is not covered with this: consider the following code:

F[k_] := 1 /; (k == 1);

F[k_] := 2  /; (k > 1);

F[k_] := A[k] ;

F[k_] := B[k] ;

DownValues[F]

In Mathics, the result is

{HoldPattern[F[k_]] ⧴ B[k]}

because the four lines sets over the same LHS pattern. On the other hand, the same code in WMA results in

{HoldPattern[F[k_]] :> 1 /; k == 1, HoldPattern[F[k_]] :> 2 /; k > 1, HoldPattern[F[k_]] :> B[k]}

so rules with the same LHS but different RHS is also overwritten, except if the RHS is a Condition expression.

[rocky]

Still, there is something that is not covered with this: consider the following code:

F[k_] := 1 /; (k == 1);

F[k_] := 2  /; (k > 1);

F[k_] := A[k] ;

F[k_] := B[k] ;

DownValues[F]

In Mathics, the result is

{HoldPattern[F[k_]] ⧴ B[k]}

because the four lines sets over the same LHS pattern. On the other hand, the same code in WMA results in

{HoldPattern[F[k_]] :> 1 /; k == 1, HoldPattern[F[k_]] :> 2 /; k > 1, HoldPattern[F[k_]] :> B[k]}

so rules with the same LHS but different RHS is also overwritten, except if the RHS is a Condition expression.

Maybe ask on https://mathematica.stackexchange.com/ what is up here and more generally how to think about how WL groups assignment categories?

[mmatera]

Actually, I am looking there, but at existing related questions.