Thanks for your answers. - Henry Lenzi
On Sun, Jul 27, 2014 at 2:36 AM, Matthew Butterick <[email protected]> wrote: > The REPL automatically uses the current namespace, which is why you can > casually use eval there without specifying a namespace. [1] > > But if you're using eval in the definitions window, you need to give it a > namespace, otherwise you'll get "unbound identifier" errors. > > In this case, the namespace you want is the one you're already in. So rather > than using (make-base-namespace), which will give you an new namespace [2], > you need a namespace anchor. To make an anchor, put this in your > definitions: > > (define-namespace-anchor a) > > > And then to use the anchor, change your `map` to this: > > (map (λ(str) (eval str (namespace-anchor->namespace a))) > '((eval *med-name*) line *quant-str* pl) ) > > > And it works. > > PS I assume you have a reason for preferring eval to, say, a hash. > > > [1] > http://docs.racket-lang.org/guide/eval.html?q=namespaces#%28part._namespaces%29 > > [2] > http://docs.racket-lang.org/reference/Namespaces.html?q=make-base-namespace&q=namespaces#%28def._%28%28lib._racket%2Fprivate%2Fbase..rkt%29._make-base-namespace%29%29 > > > > On Jul 26, 2014, at 8:10 PM, Henry Lenzi <[email protected]> wrote: > > #lang racket > > #| > > Dear Racketeers - > > I would like to create a little function > that would write a line of a medical recipe. > > I would pass to "read" a shorthand form, > and the program would expand the text. Like so: > > When I answer "hctz25" and "30", it would print: > "Hydrochlorothiazide 25mg ----------- 30 pills". > > But I'm facing problems related to: > - use of "map" with "eval" in the definition area (namespace issues...) > See below. > |# > > > (require scheme/base) ; Is this necessary? > (define this-namespace (make-base-namespace)) > > (define hctz25 "Hydroclorothiazide 25mg") > (define line "-----------") > (define pl "pills") > > (define *med-name* 'NIL) ; *med-name* has global scope - this is on purpose > (define *med-name-str* "") ; *med-name-str* has global scope > > (define (ask-med-name) > (print "Medication") (newline) > (set! *med-name* (read)) > (set! *med-name-str* (symbol->string *med-name*))) > > (define *quant* 0) (define *quant-str* " ") > > (define (ask-quant) > (print "Quantity") (newline) > (and > (set! *quant* (read)) (unless (number? *quant*) (error "It's not a > number!"))) > (set! *quant-str* (number->string *quant*))) > > (define (ask) > (ask-med-name) > (ask-quant)) > (ask) > > #| > Where's the problem? > In the REPL, I can do this: > > (map eval '((eval *med-name*) line *quant-str* pl)) > > '("Hydrochlorothiazide 25mg" "-----------" "30" "pills") > > or this: > > (string-join (map eval '((eval *med-name*) line *quant-str* pl))) > > > "Hydrochlorothiazide 25mg ----------- 30 pills" > > > But, because of the namespace issues associated with "eval", I'm not > able to do it in the definition area. > > I have no clue as to what the syntax should be. > > Thanks for any help. > > Henry Lenzi > > |# > ____________________ > Racket Users list: > http://lists.racket-lang.org/users > > > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users > ____________________ Racket Users list: http://lists.racket-lang.org/users
