A demonstration of a merging nonterminals in define-union-language

lmerge

#lang racket

(provide LMerge)
(require redex/reduction-semantics
         (only-in redex/private/matcher compiled-lang-lang))

(define-language LBase
  (e (+ e e)
     number))

(define-extended-language L1 LBase
  (e ....
     (- e e)))

(define-extended-language L2 LBase
  (e ....
     (* e e)))

;; Untagged merge of two languages that define the same nonterminal
(define-union-language LMerge L1 L2)

;; Tagged merge of two extended languages that define the same
;; nonterminal
(define-union-language LMerge2 (f. L1) (d. L2))

(redex-match? LBase e (term (+ 1 1)))

(redex-match? LMerge e (term (* 1 1)))
(redex-match? LMerge e (term (- 1 1)))
(redex-match? LMerge e (term (+ 1 1)))
(redex-match? LMerge e (term (^ 1 1)))

(compiled-lang-lang LMerge)
(compiled-lang-lang LMerge2)