Function object
In Ruby, several objects can be considered function objects, in particular Method and Proc objects. Ruby also has two kinds of objects that can be thought of as semi-function objects: UnboundMethod and block. UnboundMethods must first be bound to an object (thus becoming a Method) before they can be used as a function object. Blocks can be called like function objects, but to be used in any other capacity as an object (e.g. passed as an argument) they must first be converted to a Proc. More recently, symbols (accessed via the literal unary indicator codice_35) can also be converted to codice_36s. Using Ruby's unary codice_37 operator—equivalent to calling codice_38 on an object, and assuming that method exists—the Ruby Extensions Project created a simple hack.
Ruby (programming language)
In 1999, the first English language mailing list "ruby-talk" began, which signaled a growing interest in the language outside Japan. In this same year, Matsumoto and Keiju Ishitsuka wrote the first book on Ruby, "The Object-oriented Scripting Language Ruby" (オブジェクト指向スクリプト言語 Ruby), which was published in Japan in October 1999. It would be followed in the early 2000s by around 20 books on Ruby published in Japanese.