Addison-Wesley Professional Ruby Series Writing Efficient Ruby Code

Chapter . Runtime Complexity of Ruby Language Constructs

Ruby is a highly dynamic language: Almost all language entities are first-class citizens in that they can be created, changed, and destroyed at runtime. This comprises classes, modules, methods, constants, and class and instance variables. Only local variables are second-class citizens in Ruby: Whether a name refers to a local variable is determined at parse time.

Not surprisingly, this flexibility has implications in terms of performance: It is impossible to bind a given name to a fixed memory address (or to a fixed relative offset in a relocation table) at program load time. Thus, whenever a name is used in Ruby code, the Ruby interpreter needs to search for the object to which the code ...