str:contains? and containsp

README.md

@@ -13,7 +13,6 @@ or `str:concat strings` instead of an unusual `format` construct; one discoverab
   easier to feed pipes and arrows.
 
 <!-- markdown-toc start - Don't edit this section. Run M-x markdown-toc-generate-toc again -->
-
 **Table of Contents**
 
 - [A modern and consistent Common Lisp string manipulation library](#a-modern-and-consistent-common-lisp-string-manipulation-library)
@@ -36,6 +35,7 @@ or `str:concat strings` instead of an unusual `format` construct; one discoverab
             - [blank?, blankp `(s)`](#blank-blankp-s)
             - [starts-with?, starts-with-p `(start s &key ignore-case)`](#starts-with-starts-with-p-start-s-key-ignore-case)
             - [ends-with?, ends-with-p `(end s &key ignore-case)`](#ends-with-ends-with-p-end-s-key-ignore-case)
+            - [contains?, containsp `(substring s &key (ignore-case nil))`](#contains-containsp-substring-s-key-ignore-case-nil)
         - [Others](#others)
             - [replace `(old new s)`](#replace-old-new-s)
     - [Dev and test](#dev-and-test)
@@ -184,6 +184,15 @@ True if `s` ends with the substring `end`. Ignore case by default.
 
     (ends-with? "bar" "foobar") ;; => T
 
+#### contains?, containsp `(substring s &key (ignore-case nil))`
+
+Return true if `s` contains `substring`, nil otherwise. Ignore the
+case with `:ignore-case t` (don't ignore by default).
+
+Based on a simple call to the built-in `search` (which returns the
+position of the substring).
+
+
 ### Others
 
 #### replace `(old new s)`

str.lisp

@@ -2,6 +2,8 @@
 (defpackage str
   (:use :cl)
   (:export
+   :contains?
+   :containsp
    :trim-left
    :trim-right
    :trim
@@ -132,3 +134,21 @@
       (funcall fn s end :start1 (- (length s) (length end))))))
 
 (setf (fdefinition 'ends-with-p) #'ends-with?)
+
+(defun contains? (substring s &key (ignore-case nil))
+  "Return `t` if `s` contains `substring`, nil otherwise. Ignore the case with `:ignore-case t`.
+A simple call to the built-in `search` (which returns the position of the substring)."
+  (let ((a (if ignore-case
+               (string-downcase substring)
+               substring))
+        (b (if ignore-case
+               (string-downcase s)
+               s)))
+    ;; weird case: (search "" nil) => 0
+    (if (and (blank? substring)
+             (null s))
+        nil
+        (if (search a b)
+            t))))
+
+(setf (fdefinition 'containsp) #'contains?)

test-str.lisp

@@ -108,7 +108,7 @@
 2
 " (unlines '("1" "2" ""))))
 
-(subtest "Starts-with"
+(subtest "starts-with?"
   (ok (starts-with? "foo" "foobar") "default case")
   (ok (starts-with? "" "foo") "with blank start")
   (ok (not (starts-with? "rs" "")) "with blank s")
@@ -118,11 +118,21 @@
   (ok (starts-with-p "f" "foo") "starts-with-p alias")
   (ok (starts-with? "FOO" "foobar" :ignore-case t) "ignore case"))
 
-(subtest "ends-with"
+(subtest "ends-with?"
   (ok (ends-with? "bar" "foobar") "default case")
   (ok (ends-with-p "bar" "foobar") "ends-with-p alias")
   (ok (not (ends-with? "BAR" "foobar")) "don't ignore case")
   (ok (ends-with? "BAR" "foobar" :ignore-case t) "ignore case"))
 
+(subtest "contains?"
+  (ok (contains? "foo" "blafoobar") "default")
+  (ok (not (contains? "foo" "")) "with no string")
+  (ok (not (contains? "" nil)) "a blank substring in a nil str")
+  (ok (not (contains? "foo" nil)) "with string nil")
+  (ok (not (contains? "Foo" "blafoobar")) "with case")
+  (ok (contains? "Foo" "blafoobar" :ignore-case t) "ignore case")
+  (ok (containsp "Foo" "blafoobar" :ignore-case t) "containsp alias")
+  )
+
 ;; prove end
 (finalize)