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Merge pull request #1114 from ianthehenry/drop-from-end 

drop with a negative count now drops from the end
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Calvin Rose 2023-04-24 09:16:10 -05:00 committed by GitHub
parent 3641c8f60a 54b54f85f3
commit 4ed3f2c662
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2 changed files with 14 additions and 8 deletions
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13
src/boot/boot.janet
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@ -1140,16 +1140,17 @@
(take-until (complement pred) ind))
(defn drop
``Drop the first n elements in an indexed or bytes type. Returns a new tuple or string
instance, respectively.``
``Drop the first `n elements in an indexed or bytes type. Returns a new tuple or string
instance, respectively. If `n` is negative, drops the last `n` elements instead.``
[n ind]
(def use-str (bytes? ind))
(def f (if use-str string/slice tuple/slice))
(def len (length ind))
# make sure start is in [0, len]
(def m (if (> n 0) n 0))
(def start (if (> m len) len m))
(f ind start -1))
(def [start end]
(if (>= n 0)
[(min n len) len]
[0 (max 0 (+ len n))]))
(f ind start end))
(defn drop-until
"Same as `(drop-while (complement pred) ind)`."

9
test/suite0005.janet
View File

@ -83,8 +83,13 @@
(assert (deep= (drop 10 []) []) "drop 2")
(assert (deep= (drop 0 [1 2 3 4 5]) [1 2 3 4 5]) "drop 3")
(assert (deep= (drop 10 [1 2 3]) []) "drop 4")
(assert (deep= (drop -2 [:a :b :c]) [:a :b :c]) "drop 5")
(assert-error :invalid-type (drop 3 {}) "drop 6")
(assert (deep= (drop -1 [1 2 3]) [1 2]) "drop 5")
(assert (deep= (drop -10 [1 2 3]) []) "drop 6")
(assert (deep= (drop 1 "abc") "bc") "drop 7")
(assert (deep= (drop 10 "abc") "") "drop 8")
(assert (deep= (drop -1 "abc") "ab") "drop 9")
(assert (deep= (drop -10 "abc") "") "drop 10")
(assert-error :invalid-type (drop 3 {}) "drop 11")
# drop-until