Yes this is a good point, but how can I avoid this blowing up problem
if I'm not handling a single variable (just as the code in my last
post)?
On 12月16日, 上午5时09分, Cedric Greevey <cgree...@gmail.com> wrote:
> On Thu, Dec 15, 2011 at 1:54 PM, Alan Malloy <a...@malloys.org> wrote:
> > This will print all the debug information at compile time, which is
> > usually not what you want. I have a little macro I use called ?, which
> > looks like:
>
> > (defmacro ? [x]
> > `(let [x# ~x]
> > (prn '~x '~'is x#)
> > x#))
>
> > You could add file and line information to this fairly simply:
>
> > (defmacro ? [x]
> > (let [line (:line (meta &form))
> > file *file*]
> > `(let [x# ~x]
> > (println (pr-str '~x) "is" (pr-str x#)
> > (str "; (" ~file ":" ~line ")"))
> > x#)))
>
> > And use it like so:
>
> > user> (let [x 10]
> > (+ 5 (? x)))
> > x is 10 ; (NO_SOURCE_FILE:1)
> > 15
>
> You might want to change
>
> (pr-str x#)
>
> to something like
>
> (pr-str
> (if (seq? x#)
> (let [s (Object.)]
> (if (= (nth x# 11 s) s)
> x#
> (concat (take 10 x#) ['...])))
> x#))
>
> which will print sequences longer than ten elements as (1 2 3 4 5 6 7
> 8 9 10 ...) and prevent infinite seqs from blowing things up. Or more
> generally you might want to go through pprint which lets you set
> *print-len* and *print-level* to generally control the printing of
> very large and/or deeply-nested structures. But that adds a new
> dependency that needs to be required anywhere you use the macro ...
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