[racket] Use of map and eval to evaluate symbol in namespace

#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

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