Data update

Task/String-matching/ArkScript/string-matching.ark

@@ -0,0 +1,6 @@
+(assert (= 0 (string:find "abcd" "ab")) "abcd starts with ab")
+(assert (= 6 (string:find "hello world" "world")) "world is located at 6")
+(assert (= -1 (string:find "abcd" "zn")) "abcd does not contain zn")
+(assert (= -1 (string:find "abab" "bb")) "abab does not contain bb")
+(assert (= 0 (string:find "abab" "ab")) "abab contains ab")
+(assert (= 2 (string:find "abab" "ab" 1)) "starting lookup at index 1, we found ab at position 2")

Task/String-matching/DuckDB/string-matching.duckdb

@@ -0,0 +1,17 @@
+# Return a list of the indices of all occurrences (including overlapping occurrences)
+create or replace function string_positions(haystack, needle) as (
+  WITH RECURSIVE etc AS (
+    SELECT
+      position(needle IN haystack) AS start_pos,
+      0 as s
+    UNION ALL
+    SELECT
+      position(needle IN substr(haystack, start_pos + 1)) + start_pos AS start_pos,
+      start_pos as s
+    FROM etc
+    WHERE start_pos != s
+  )
+  SELECT coalesce(array_agg(start_pos order by start_pos),[]::BIGINT[])
+  FROM etc
+  WHERE start_pos > 0 and s != start_pos
+);

Task/String-matching/R/string-matching.r

@@ -0,0 +1,14 @@
+startsWith("foobar", "foo")
+startsWith("barbaz", "bax")
+grepl("bar", "foobarqux") #Note order of arguments isn't always the same
+grepl("baz", "foobarqux")
+endsWith("foobar", "bar")
+endsWith("foobar", "baz")
+
+regexpr("bar", "barbazbarbax") #Only returns position of first match
+
+regexpr("foo", "barbazbarbax") #Returns -1 if no match exists
+
+gregexpr("bar", "barbazbarbax") #Returns positions of all matches
+
+gregexpr("foo", "barbazbarbax") #Same output as regexpr() if no match, but as a length-1 list rather than a vector