On Fri, Dec 9, 2011 at 4:53 PM, Stephen Chang <[email protected]> wrote: > Say I have the following program: > > > #lang racket > > (define-for-syntax (loc-expand stx) (local-expand stx 'expression '())) > > (define-syntax (my-begin stx) > (syntax-case stx () > [(_ e ...) > (with-syntax ([(x ...) (map loc-expand (syntax->list #'(e ...)))]) > #'(begin x ...))])) > > (define-syntax (my-lambda1 stx) > (syntax-case stx () > [(_ args body ...) > #'(lambda args (my-begin body ...))]))
`my-lambda1' does the local expansion after the `lambda' form introduces the bindings from `args' into the environment. > > (define-syntax (my-lambda2 stx) > (syntax-case stx () > [(_ args body ...) > (with-syntax ([(x ...) (map loc-expand (syntax->list #'(body ...)))]) > #'(lambda args (begin x ...)))])) `my-lambda2' does the local expansion before the `lambda' form introduces the bindings from `args' into the environment, meaning that there's no binding yet for any of the arguments. > > An expression (my-lambda1 (y) (+ y 1)) works fine but (my-lambda2 (y) > (+ y 1)) produces the error: > > expand: unbound identifier in module in: y > > > I can't figure out why this is the case. Anyone know? > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/dev -- sam th [email protected] _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
