Question 0:
In collects/racket/stream.rkt, `stream-map' is defined as:
(define (stream-map f s)
(unless (procedure? f) (raise-argument-error 'stream-map "procedure?" f))
(unless (stream? s) (raise-argument-error 'stream-map "stream?" s))
(let loop ([s s])
(cond
[(stream-empty? s) empty-stream]
[else (stream-cons (call-with-values (lambda () (stream-first s)) f)
(loop (stream-rest s)))])))
I don't understand the difference between:
(call-with-values (lambda () (stream-first s)) f)
and
(f (stream-first s))
because the contract for `stream-first' is:
(stream-first s) → any
s : (and/c stream? (not/c stream-empty?))
Which seems to me to just return a single value. I was taking a second look at
my changes to `stream-map' which add support for multiple streams. I noticed
this unusual snippet as I rebased onto the latest version of plt/master.
Question 1:
Would it make more sense to simply update all the sequence procedures to handle
multiple sequences? Is there a circumstance where it doesn't make sense to
handle multiple sequences in a sequence procedure such as `sequence-map'?
I figure that the sequence procedures don't support multiple sequences is just
lack of interest. Do most people just use the `for' macros in these cases?
--
Dan King
College of Computer and Information Science
Northeastern University
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