On Sun, Jun 21, 2015 at 7:13 PM, Bahman Movaqar <b.mova...@gmail.com> wrote:
> On Monday, 22 June 2015 02:34:43 UTC+4:30, Bahman Movaqar wrote:
>> Assuming
>>
>> (define my-list ("a" 1 "b" 2.5 "c" #t "d" "hi"))
>>
>> what is the idiomatic way to convert `my-list` into the following?
>>
>> "[a=1][b=2.5][c=#t][d=hi]"
>>
>> I thought of `FORMAT` but apparently the `{}` (for recursion) are not
>> available.
>> For example, in CL `(format nil "~{[~a:~a]~}" my-list)` would do the trick.
>
> This is what I've come up with so far; but it doesn't feel idiomatic at all
> :-)
>
> (string-join
> (unfold null-list?
> (lambda (x) (format "[~a=~a]" (first x) (second x)))
> (lambda (x) (cdr (cdr x)))
> my-list)
> "")
This might be a bit more rackety:
(apply string-append
(for/list ([(k v) (apply hash my-list)])
(format "[~a=~a]" k v)))
It relies on the (happy?) accident that `hash` happens to accept a
flat list. This also makes it more expensive than a version that
doesn't use a hash.
Here's a hash-less alternative (though this one does use an unstable library):
(require unstable/sequence)
(apply string-append
(for/list ([slice (in-slice 2 my-list)])
(format "[~a=~a]" (car slice) (cadr slice)))))
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