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). ____________________ Racket Users list: http://lists.racket-lang.org/users
