mogenslund/liquid

(doall (map inc [1 2 3])) evals to lazy seq

maacl opened this issue · 4 comments

maacl commented

doall should force the sequence.

mogenslund commented

I think it does. It is just still a lazy sequence. If you compare with the repl, I think the repl applies a pr-str to the result, which prints the evaluated sequence. Try the following in a repl:

(type (doall (map inc [1 2 3])))

it will evaluate to clojure.lang.LazySeq.

In Liquid try:

(doall (map #(println %) [1 2 3]))

Notice the sideeffect is executed!

Last. In Liquid do

(pr-str (doall (map inc [1 2 3])))

Now you get the correct output.

I can change my code to apply pr-str automatically, but I think I prefer it as an explicit option to avoid printing endless sequences.

maacl commented

clojure.lang.LazySeq is its type, it is not a meaningful representation. It think you should consider emulating CIDER's behaviour when it comes to long/infinite sequences.

mogenslund commented

I think you have a point.

I will try out how CIDER handles my edge cases and adjust my local implementation accordingly and use it for some days to check if there are any unexpected side effects.

mogenslund commented

I have made a commit now. It uses pr-str when the output is not a string. Also pr-str truncates long lists using the global *print-length* variable. (I did not know that one, but found it by inspecting CIDERs source code.)

I also think it works better now. Thank you @maacl

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