For the archives the functions eval-for-meta ; evaluate expression in given phase and return result eval-for-syntax ; evaluate expression in phase 1 and return result eval-form-for-meta ; evaluate form in given phase eval-form-for-syntax ; evaluate form in phase 1 syntax-value ; return the value associated with a syntax binding in a given phase
are available here: https://github.com/soegaard/meta/blob/master/expander/transformer.rkt /Jens Axel 2014-07-20 1:39 GMT+02:00 Jens Axel Søgaard <jensa...@soegaard.net>: > 2014-07-20 1:19 GMT+02:00 Matthias Felleisen <matth...@ccs.neu.edu>: >> >> Can't you just put forms2 into a constructed module that requires the >> desired module at the phase where you want it? -- Matthias > > That would be tricky. I am writing an interpreter that evaluates > Racket bytecode represented as zo-structures. > > The main entry is: > > ; eval-zo : compilation-top [namespace] -> values(s) > (define (eval-zo zo [ns (make-start-namespace)]) > (unless (compilation-top? zo) > (error 'eval-zo "expected a compilation-top, got ~a" zo)) > ; evaluation always occur within a top-level namespace > (parameterize ([current-namespace ns]) > (eval-top zo))) > > The structure of the interpreter is a straight forward recursive descent. > The "phase 0" forms and expressions are done and works fine. > I have also managed to evaluate the stxs part of the prefix. > The instruction I need shift-phase for is seq-for-syntax. > > From the docs on begin-for-syntax: > Evaluation of an expr within begin-for-syntax is parameterized to > set current-namespace as in let-syntax. > From the docs on (let-syntax ([id trans-expr] ...) body ...+) > The evaluation of each trans-expr is parameterized to > set current-namespace to a namespace that shares > bindings and variables with the namespace being used to > expand the let-syntax form, except that its base phase is one greater. > > > Here is what I'd like to write: > > (define (eval-form form globs stack closed stx-ht) > (match form > ... > [(struct seq-for-syntax (forms prefix max-let-depth dummy)) > ; push the prefix > (define array (eval-prefix prefix stx-ht)) > (define new-stack (mlist array stack)) > ; shift phase and evalate each form > (parameterize ([current-namespace (shift-phase (current-namespace) +1)]) > (for ([form (in-list forms)]) > (let-syntaxes ([() (begin (eval-form (car forms) globs > new-stack closed stx-ht) > (values))]) > (void))))] > > /Jens Axel > >> On Jul 19, 2014, at 3:52 PM, Jens Axel Søgaard wrote: >> >>> I am looking for a way to change the base phase of a namespace. >>> Or perhaps to make a new namespace with the same mappings except a >>> shift in phases. >>> I hope I have missed a trick, but I couldn't find a >>> namespace-shift-phase in the docs. >>> >>> Consider the following program which defines a variable x to 0, 1, 2, and, 3 >>> in phases 0, 1, 2, and, 3 respectively. It does so by evalunting the >>> forms in forms. >>> >>> Then it displays the values of x in phases 1 and 2 with the results 1 and 2. >>> It does so by evaluating the forms in forms2. >>> >>> I'd like to shift the base phase of the namespace (or make a copy with >>> new base phase), >>> so evaluating the forms in forms2 again will give results 2 and 3. >>> >>> #lang racket >>> (define (eval* forms [ns (current-namespace)]) >>> (for ([form forms]) >>> (displayln (~a "> " form)) >>> (eval form ns))) >>> >>> (define forms '((module m0 racket (provide x) (define x 0)) >>> (module m1 racket (provide x) (define x 1)) >>> (module m2 racket (provide x) (define x 2)) >>> (module m3 racket (provide x) (define x 3)) >>> (require (for-meta 0 'm0)) >>> (require (for-meta 1 'm1)) >>> (require (for-meta 2 'm2)) >>> (require (for-meta 3 'm3)))) >>> >>> (define forms2 '(; display the value of x in phase 1 >>> (define-syntaxes () (begin (displayln x) (values))) >>> ; display the value of x in phase 2 >>> (define-syntaxes () (begin (let-syntaxes ([() (begin >>> (displayln x) (values))]) >>> (void)) >>> (values))))) >>> >>> (define ns (make-base-empty-namespace)) >>> (parameterize ([current-namespace ns]) >>> ; setup the namespace >>> (namespace-require '(for-meta 0 racket/base)) >>> (namespace-require '(for-meta 1 racket/base)) >>> (namespace-require '(for-meta 2 racket/base)) >>> (namespace-require '(for-meta 3 racket/base)) >>> ; declare and require the modules >>> (eval* forms) >>> ; display the value of x in phase 1 and 2 >>> (eval* forms2) ; displays 1 and 2 >>> ; (namespace-shift-phase ns +1) ; on the wish list >>> ; (eval* forms2) ; would display 2 and 3 >>> ) >>> >>> The output is: >>> >>>> (module m0 racket (provide x) (define x 0)) >>>> (module m1 racket (provide x) (define x 1)) >>>> (module m2 racket (provide x) (define x 2)) >>>> (module m3 racket (provide x) (define x 3)) >>>> (require (for-meta 0 (quote m0))) >>>> (require (for-meta 1 (quote m1))) >>>> (require (for-meta 2 (quote m2))) >>>> (require (for-meta 3 (quote m3))) >>>> (define-syntaxes () (begin (displayln x) (values))) >>> 1 >>>> (define-syntaxes () (begin (let-syntaxes ((() (begin (displayln x) >>>> (values)))) (void)) (values))) >>> 2 >>> >>> -- >>> Jens Axel Søgaard >>> >>> ____________________ >>> Racket Users list: >>> http://lists.racket-lang.org/users >> > > > > -- > -- > Jens Axel Søgaard -- -- Jens Axel Søgaard ____________________ Racket Users list: http://lists.racket-lang.org/users
