How to check if a string s1 is a substring of another string s2?

For example (test-substring "f t" "df tj") --> t, (test-substring "ft" "df tj") --> nil.


The standard Emacs Lisp approach is regular expression matching:

(string-match-p (regexp-quote needle) haystack)

cl-search can do that (and also returns the index of the substring, if found):

ELISP> (cl-search "f t" "df tj")
1 (#o1, #x1, ?\C-a)
ELISP> (cl-search "ft" "df tj")
  • 1
    Thanks, this correctly answers the question. Let me wait for some other solutions. – Name Aug 19 '15 at 14:03

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