In Common Lisp, is there a predicate to test whether a given character is part of a string? Or more generally, if an element is a member of a vector?
Something like:
(char-in #\o "foo")
I was able to implement it as
(defun char-in (c s)
(member c (coerce s 'list)))
Is there a better way?
Strings are vectors. Vectors are sequences.
Strings are vectors and sequences. So all operations for them apply:
Find an item:
CL-USER 59 > (find #\X "fooXbar")
#\X
CL-USER 60 > (find #\x "fooXbar")
NIL
Find the position of an item:
CL-USER 61 > (position #\x "fooXbar")
NIL
CL-USER 62 > (position #\X "fooXbar")
3
Search for a subsequence:
CL-USER 63 > (search "X" "fooXbar")
3
CL-USER 64 > (search "x" "fooXbar")
NIL
Default test is EQL
All functions use EQL as the default test, but you can use another one - for example a case-insensitive find would be:
CL-USER 65 > (find #\x "fooXbar" :test #'char-equal)
#\X