$ irb
irb(main):002:0> a = "abc"
"abc"
irb(main):004:0> a.methods
["~", "==", "kconv", "slice", "squeeze", "strip", "%", "intern", "===", "capitalize!", "to_f", "eql?", "empty?", "toeuc", "each_byte", "upcase!", "dup", "rindex", "length", "tr_s", "to_i", "chop", "concat", "squeeze!", "chomp!", "sub", "reverse", "to_s", "capitalize", "upto", "*", "tr_s!", "oct", "upcase", "next", "+", "strip!", "=~", "rjust", "slice!", "count", "hash", "succ", "sub!", "scan", "swapcase!", "to_str", "tosjis", "sum", "delete", "crypt", "downcase!", "[]", "replace", "size", "chomp", "[]=", "tojis", "each_line", "clone", "index", "<<", "tr", "gsub", "reverse!", "inspect", "swapcase", "unpack", "each", "delete!", "center", "split", "downcase", "next!", "chop!", "tr!", "dump", "succ!", "include?", "gsub!", "<=>", "ljust", "hex", "min", "find_all", "entries", "each_with_index", "map", "detect", "collect", "find", "to_a", "member?", "reject", "grep", "max", "select", "sort", "<", ">", "between?", ">=", "<=", "singleton_methods", "tainted?", "method", "methods", "nil?", "is_a?", "instance_of?", "class", "instance_variables", "send", "frozen?", "__id__", "__send__", "protected_methods", "untaint", "respond_to?", "public_methods", "taint", "equal?", "kind_of?", "display", "instance_eval", "type", "freeze", "id", "extend", "private_methods"]
irb(main):005:0> a.instance_variables
[]
irb(main):006:0> load "prac0401.rb"
true
irb(main):008:0> t1 = Triangle.new(1,2)
#<Triangle:0x402c9e68 @takasa=2, @teihen=1>
irb(main):009:0> t1.instance_variables
["@takasa", "@teihen"]
irb(main):010:0> Triangle.instance_variables
[]
irb(main):012:0> Triangle.kind_of?(Class)
true
irb(main):013:0> Triangle.kind_of?(Module)
true
irb(main):014:0> Triangle.kind_of?(Object)
true
irb(main):015:0> Triangle.kind_of?(Array)
false
irb(main):016:0> Triangle.kind_of?(Method)
false
irb(main):017:0> Triangle.kind_of?(Proc)
false