Tim,
I don't think your version of the signature supports variadic defaults
well. Also, I'd (initially) implement fnil differently that Rich.
Here's my fnil-2 that I *suspect* has the intended behavior
(defn fnil-2
[f & defaults]
(fn[& args]
(let [used-args (map (fn [default-value value]
(if value value default-value))
defaults args)]
(apply f used-args))))
user=>(def nil+ (fnil-2 + 0 1 2 3 4 5 6))
user=>(nil+ nil)
0
user=>(nil+ 0 nil)
1
user=>(nil+ 0 0 nil)
2
user=>(nil+ 0 0 0 nil)
3
...
user=>(nil+ 0 0 0 0 0 0 nil)
6
;This example exceeds the provided # of nil values
user=>(nil+ 0 0 0 0 0 0 0 nil)
NPE
You get the idea. Also, Rich's style matches the signature of partial
better, which I personally prefer.
Just my $.02
Sean
On Jan 1, 6:45 pm, Timothy Pratley <timothyprat...@gmail.com> wrote:
> On Dec 13, 1:24 am, Rich Hickey <richhic...@gmail.com> wrote:
>
> > fnil seems to me to have greater utility than patching all functions
> > that apply functions with default-supplying arguments.
>
> Hi Rich,
>
> To further comment on fnil, after having experimented with it a bit
> now, I've come to slightly prefer specifying the 'default' value
> before the function just because I think it reads nicer:
> (fnil 0 inc) ;; instead of (fnil inc 0)
> (fnil [] conj) ;; instead of (fnil conj [])
> I read it as "fill nil with 0 for inc"
> I suppose "fill nil of inc with 0" makes just as much sense but I find
> "inc 0" leads my eye to believe 0 will always be passed to inc,
> whereas "0 inc" does not. Putting the function last makes it clearer
> to me that the 0 is conditional. It also looks more like if nil 0.
> This contrasts with get, which makes perfect sense having the default
> last, but I think at this point fnil and get are sufficiently far
> apart that a different argument order would not be surprising.
>
> Just a small observation I thought I'd raise for discussion to see
> what preferences are out there if this function becomes widespread.
>
> Regards,
> Tim.
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