casecmp?

Returns true if str and other_str are equal after Unicode case folding, false if they are not equal.

"aBcDeF".casecmp?("abcde")     #=> false
"aBcDeF".casecmp?("abcdef")    #=> true
"aBcDeF".casecmp?("abcdefg")   #=> false
"abcdef".casecmp?("ABCDEF")    #=> true
"\u{e4 f6 fc}".casecmp?("\u{c4 d6 dc}")   #=> true

nil is returned if the two strings have incompatible encodings, or if other_str is not a string.

"foo".casecmp?(2)   #=> nil
"\u{e4 f6 fc}".encode("ISO-8859-1").casecmp?("\u{c4 d6 dc}")   #=> nil