The list:takeWhile function

List.ark

@@ -245,6 +245,33 @@
     _output
 }))
 
+###
+# @meta List
+# @brief Take the first n elements of
+# @param _L the list to work on
+# @param _f the predicate
+# @details The original list is left unmodified.
+# =begin
+# (print (takeWhile [1 2 3 4 5 6 7 8 9 10] (fun (a) (< a 4))))  # [1 2 3]
+# =end
+# @author https://github.com/rakista112
+##
+(let list:takeWhile (fun (_L _f) {
+    (mut _index 0)
+    (mut _output [])
+    (mut continue true)
+    (while (and (< _index (len _L)) continue)
+        (if (_f (@ _L _index))
+            {
+                (set _output (append _output (@ _L _index)))
+                (set _index (+ 1 _index))
+            }
+            (set continue false)
+        )
+    )
+    _output
+}))
+
 ###
 # @brief Unzip a list of [[a b] [c d]...] into [[a c ...] [b d ...]]
 # @param _L the list to work on

tests/list-tests.ark

@@ -51,6 +51,11 @@
     (set tests (assert-eq (list:take a 1) [1] "take" tests))
     (set tests (assert-eq (list:take a 100) a "take" tests))
 
+    (set tests (assert-eq (list:takeWhile a (fun (c) (< c 0))) [] "takeWhile" tests))
+    (set tests (assert-eq (list:takeWhile a (fun (c) (< c 2))) [1] "takeWhile" tests))
+    (set tests (assert-eq (list:takeWhile a (fun (c) (< c 3))) [1 2] "takeWhile" tests))
+    (set tests (assert-eq (list:takeWhile a (fun (c) (< c 5))) [1 2 3] "takeWhile" tests))
+
     (set tests (assert-eq (list:unzip zipped) [[1 2 3 4] [5 6 7 8]] "unzip" tests))
     (set tests (assert-eq (list:unzip []) [[] []] "unzip" tests))