casecmp

        # Symbol.casecmp

(from ruby core)
---
    casecmp(other_symbol) -> -1, 0, 1, or nil

---

Case-insensitive version of [Symbol#<=>](#method-i-3C-3D-3E):

    :aBcDeF.casecmp(:abcde)   # => 1
    :aBcDeF.casecmp(:abcdef)  # => 0
    :aBcDeF.casecmp(:abcdefg) # => -1
    :abcdef.casecmp(:ABCDEF)  # => 0

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

Currently, case-insensitivity only works on characters A-Z/a-z, not all
of Unicode. This is different from Symbol#casecmp?.

Related: Symbol#casecmp?.