Hi all,
I've been experimenting with a custom system of managed local variables,
and I came up with a hygiene test case that was failing. So then I tried
the same test case with plain Racket variables, and it failed that way too.
Here's a minimalistic example.
Basically, this is a curried macro: The user supplies a variable and gets a
macro out, and then the user calls that macro. Can the second macro bind
the variable the user supplied to the first one? I thought it would be able
to, but this doesn't currently seem to be case on Racket v7.8 [cs].
Could anyone explain what's going on with this? Is there a workaround if I
want to write this kind of macro? Should I file a bug in Racket? This looks
pretty close to R5RS Scheme, so I wonder what the situation in the broader
Scheme world is like, too.
#lang racket
(require rackunit)
(define-syntax-rule
(let-second-and-create-let-third var let-third body-of-let-second)
(let-syntax ([let-third
(syntax-rules ()
[(let-third body-of-let-third)
(let ([var "third"])
body-of-let-third)])])
; This binding shows that the first macro *does* manage to bind
; the given variable, even though the second macro doesn't.
(let ([var "second"])
body-of-let-second)))
(check-equal?
(let ([x "first"])
(let-second-and-create-let-third x let-third
(let-third
x)))
"third"
"Test that a macro generated by a macro can bind a variable the user
supplied to the generator macro")
; FAILURE
; actual: "second"
; expected: "third"
You can also find this code in Gist form here:
https://gist.github.com/rocketnia/cb83da2cfcddbf614dfe1dfc5e08792c
Thanks in advance for any insight you have about what's going on here.
- Nia
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