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Returns a vector of [start end] offsets for substrings in s.
(defn substring-offsets
"Returns a seq of [start end] offsets for substrings in s."
[s substring]
(when-not (empty? substring)
(let [s (.toLowerCase s)
substring (.toLowerCase substring)
s-length (count s)
substring-length (count substring)]
(loop [offset 0
offsets nil]
(let [substring-start-offset (.indexOf s substring offset)]
(if (= -1 substring-start-offset)
offsets
(let [substring-end-offset (+ substring-start-offset substring-length)
bounded-substring-end-offset (min substring-end-offset s-length)
substring-from-offsets (subs s
substring-start-offset
bounded-substring-end-offset)
beginning-of-string? (= 0 substring-start-offset)
end-of-string? (= s-length substring-end-offset)
char-before-substring (when-not beginning-of-string?
(subs s
(- substring-start-offset 1)
substring-start-offset))
char-after-substring (when-not end-of-string?
(subs s
bounded-substring-end-offset
(+ 1 bounded-substring-end-offset)))]
(if (and (or beginning-of-string? (delimiter? char-before-substring))
(or end-of-string? (delimiter? char-after-substring))
(= substring substring-from-offsets))
(recur substring-end-offset
(conj offsets
[substring-start-offset bounded-substring-end-offset]))
offsets))))))))
(substring-offsets "The quick brown fox jumps over the lazy dog" "the")
;; => ([0 3] [31 34])
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