> On Oct 3, 2017, at 10:31 AM, 'Shakin Billy' via Racket Users 
> <racket-users@googlegroups.com> wrote:
> how do i access the pattern variable var at compile time (phase 1?)
> additional to an answer, could you point me to the right part of the 
> documentation? i really couldn't find it.

`var` isn't a `procedure?` during phase 1. It's just a piece of syntax. So your 
`cond`, which is evaluated in phase 1, will always fail.

But if you shift the `cond` to phase 0, by putting it inside the syntax 
template, it will work:

#lang racket
(require rackunit)
(define inp (open-input-string "12+34"))

(define-syntax (terminal stx)
  (syntax-case stx ()
    ((_ name rx)
     (if (pregexp? (syntax->datum #'rx))
         #'(define (name)
             (regexp-try-match rx inp))
         #'(error "Pregexp expected.")))))

(define-syntax (prod stx)
  (syntax-case stx ()
    ((_ prod-name (name var))
         ((procedure? var) 0)
         (else (error 'PROD-ARGUMENTS "Pregexp oder Procedure expected."))))))

(terminal digit #px"\\d")
(check-equal? (prod term (op1 digit)) 0)

(define not-a-procedure 42)
(check-exn exn:fail? (λ () (prod term (op1 not-a-procedure))))

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