--- chr

    ʸɤб 1 ХȤʸ֤ޤ㤨 
    65.chr  "A" ֤ޤ

    դʸ󤫤ʸɤˤ "A"[0] Ȥޤ
    (String#[] [String/[]] 򻲾ȤƤ)

     0  255 ϰǤʤФʤޤϰϳФ
    ƤӽФ㳰 RangeError ȯޤ

