Matthias, hello.
On 2014 Aug 5, at 14:23, Matthias Felleisen <[email protected]> wrote:
> --- 1. There was no contradiction between Sam's email (happy birthday Sam)
> and mine.
On the contrary, I thought it was useful to see, between three alternatives,
the contrast between a minimally- and a maximally-rewritten version.
> add type declarations to variables and fields and function and method
> signatures.
A good motto, which I shall endeavour to remember.
> Bottom line is then, TR is in an actual state and then there is the ideal
> that some of us have in our head where local type inference does a lot more
> and becomes almost as good as GLOBAL ti in terms of convenience. It is
> critical to keep this in mind. TR isn'f finished and it will continue to move
> from 'actual' to 'ideal'.
Keep on keeping on!
In case anyone's interested, the actual code ended up looking as below.
Thanks, all, for a most illuminating thread.
Best wishes,
Norman
----
(define-type LevelN Positive-Integer)
(define-type Backup-Log (Vectorof (Maybe LevelN)))
(require/typed db
[#:opaque Handle connection?]
[query-value (Handle String SQLType * -> SQLType)]
[query-rows (Handle String SQLType * -> (Listof (Vectorof
SQLType)))])
[...]
(: get-latest-backups/filesystem
(case->
(Handle String -> Backup-Log)
(Handle String String -> Backup-Log)))
(define (get-latest-backups/filesystem db fs [refdate #f])
;; I can't see any way to do this in a single SQL statement
(let ((parent0 (query-value db
"select parent0 from backups where filesystem=$1
and created<$2 order by created desc limit 1"
fs
(or refdate (reftime/iso8601)))))
(define-type VIL (Vector Positive-Integer LevelN))
(define idx+level : (Listof VIL)
(cast (query-rows db ; only idx=0 can have a level=0 backup
"select idx, level from backups where parent0=$1 and
idx > 0"
parent0)
(Listof VIL)))
(define length : Positive-Integer
(1+ (apply max (map (λ ([x : VIL]) (vector-ref x 0)) idx+level))))
(define result : Backup-Log
(make-vector length #f))
(for ((q : VIL (in-list idx+level)))
(vector-set! result (vector-ref q 0) (vector-ref q 1)))
result))
--
Norman Gray : http://nxg.me.uk
SUPA School of Physics and Astronomy, University of Glasgow, UK
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