Alaric Snell-Pym <[EMAIL PROTECTED]> writes:
>> It's up to the caller to supply a correct alist to the function.
>> E. g.:
> Ah, but the original problem was that the alist was read from a file,
> at run time!
Well, symbols may either be simply `eval'ed, or ``mapped'' to
their respective parameters. Since the symbols are going from
file, I'd recommend you to ``map'' them.
Given that the ``parameter object'' is indistinguishable from a
procedure of one optional argument, the ``mapping'' function
could be used to signal an error if an invalid symbol was
specified in the file. E. g.:
(define *the-mapping*
`((stdout . ,current-output-port)
(stdin . ,current-input-port)
))
(define (the-symbol->parameter sym)
(cond ((assoc sym *the-mapping*) => cdr)
(else (error "invalid parameter:" sym))))
(define (the-alist->parameters alist)
(map (lambda (pair)
(cons (the-symbol->parameter (car pair))
(cdr pair)))
alist))
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