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Task/String-matching/Common-Lisp/string-matching.lisp

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+(defun starts-with-p (str1 str2)
+  "Determine whether `str1` starts with `str2`"
+  (let ((p (search str2 str1)))
+    (and p (= 0 p))))
+
+(print (starts-with-p "foobar" "foo")) ; T
+(print (starts-with-p "foobar" "bar")) ; NIL
+
+(defun ends-with-p (str1 str2)
+  "Determine whether `str1` ends with `str2`"
+  (let ((p (mismatch str2 str1 :from-end T)))
+    (or (not p) (= 0 p))))
+
+(print (ends-with-p "foobar" "foo")) ; NIL
+(print (ends-with-p "foobar" "bar")) ; T
+
+(defun containsp (str1 str2)
+  "Determine whether `str1` contains `str2`.
+   Instead of just returning T, return a list of starting locations
+   for every occurence of `str2` in `str1`"
+   (unless (string-equal str2 "")
+     (loop for p = (search str2 str1) then (search str2 str1 :start2 (1+ p))
+           while p
+           collect p)))
+
+(print (containsp "foobar" "oba")) ; (2)
+(print (containsp "ababaBa" "ba")) ; (1 3)
+(print (containsp "foobar" "x"))   ; NIL