casecmp?

        # Symbol.casecmp?

(from ruby core)
---
    casecmp?(other_symbol) -> true, false, or nil

---

Returns `true` if `sym` and `other_symbol` 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

Returns `nil` if the two symbols have incompatible encodings, or if
`other_symbol` is not a symbol:

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

See [Case Mapping](doc/case_mapping_rdoc.html).

Related: Symbol#casecmp.