[racket] redex: default matching behavior of patterns

Just in case it was unclear I was hoping people would explicitly adorn pattern variables if they want to match the same term.

(simple integer_1 integer_1)

But if (simple integer integer) to match the same term twice is a heavily used form then so be it..

On 05/01/2012 05:52 PM, Robby Findler wrote:
> This is heavily relied on.
>
> Robby
>
> On Tue, May 1, 2012 at 6:45 PM, Jon Rafkind <rafkind at cs.utah.edu> wrote:
>> The default matching behavior of patterns in redex will try to match duplicate pattern variables to the same term. Thus
>>
>> #lang racket
>>
>> (require redex)
>>
>> (define-language Z [x integer])
>> (define-metafunction Z
>>  simple : integer integer -> integer
>>  [(simple integer integer) 1])
>>
>> (term (simple 1 2))
>>> simple: no clauses matched for (simple 1 2)
>> Won't match because the pattern (simple integer integer) will match the first `integer' to 1, and wants to the second reference to `integer' to the same thing. To get it to work I need to adorn the pattern variables with _1 and _2 to make them unique.
>>
>> (define-language Z [x integer])
>> (define-metafunction Z
>>  simple : integer integer -> integer
>>  [(simple integer_1 integer_2) 1])
>>
>> I would prefer (if possible) if the default behavior treated unadorned pattern variables as fresh so that I don't have to remember to attach a suffix. I guess this might break existing programs but I can't imagine anyone really relies on this behavior (unadorned variables matching duplicate terms).
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