igop: repl built-in functions design

[visualfc]

igop repl add pythonic built-in functions . rtype eval ...

• type

rtype(x interface{}) Type can be compared two Type

//rtypeMap = make(map[Type]reflect.Type)
type Type string
func (Type) Type() reflect.Type
func (Type) Kind() reflect.Kind

>>> rtype(100) == rtype(200)
true
>>> rtype(100) == "int"
true

• eval

eavl(expr string) (interface{},error)

  similar igop
  copy current context vars to new context and run. 
  return context ret interface{}/[]interface{} , error

>>> a := 10
>>> eval("a+1")
11,nil
>>>

• dir
  dir ?

• vars
  vars?