Hi, I am writing my first interpreter, but I am struggling with the definitions of 'define', 'let' and 'letrec'.
Here is the source code intrepreter (> 100 loc) . http://gist.github.com/487501 The problem is that 'define' requires access to the enviroment. I as understand define is equivalent to these expansions. ==== Top level. (define (foo) (... (bar) ...)) => Will be (define foo (lambda () (... (bar) ...))) ==== In a lambda environment. (define (my-proc) (define (local-proc-1) ...) (define (local-proc-2) ...) (local-proc-1) (local-proc-1)) => Will be (define my-proc (lambda () (letrec ((local-proc-1 (lambda () ...)) (local-proc-2 (lambda () ...))) (local-proc-1) (local-proc-2))) Can anyone point me how to implement this features. I am trying to implement them out of the evaluator function, but I guess that if they need access to the environment, maybe they should be inside of the evaluator method. Maybe something like this? [`(letrec ,binds ,eb) (eval-letrec binds eb env)] [`(let ,binds ,eb) (eval-let binds eb env)] ; eval for letrec: (define (eval-letrec bindings body env) (let* ((vars (map car bindings)) (exps (map cadr bindings)) (fs (map (lambda _ #f) bindings)) (env* (extended-env* env vars fs)) (vals (map (evlis env*) exps))) (env-set!* env* vars vals) (eval body env*))) ; eval for let: (define (eval-let bindings body env) (let* ((vars (map car bindings)) (exps (map cadr bindings)) (vals (map (evlis env) exps)) (env* (extended-env* env vars vals))) (eval body env*))) (define ? ) I am new in this list, so let me know if this question is "off-topic". Thx. -- ------------------------------------- Pedro Del Gallego Email : pedro.delgall...@gmail.com _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
