Abstract
B001e is a message-sending based re-implementation of the
Boolean operators and, or and not and the Boolean
expressions if and unless in pure Ruby.
Lazy Evaluation / Short-circuiting is achieved through the use
of blocks and lambda expressions.
This library contains sample re-implementations of the Boolean
operators and, or and not and the Boolean expressions
if and unless, in pure Ruby. The style is heavily
inspired by Smalltalk and its relatives: the operators become
messages that take block parameters and are sent to the
conditionals.
Operator / keyword style:
if c1 && c2 t elsif c3 ei else e end
becomes:
c1.and { c2 }.ifelse ->{ t }, ->{ c3.ifelse ->{ ei }, ->{ e } }
Every so often, there is a discussion on either the Ruby-Talk or
Ruby-Core mailinglists, whether the number of operators that are
not backed by methods should be reduced. In Ruby 1.9, ! and
!= have already become methods, but and and or are
still builtin operators and if and unless still builtin
keywords.
One argument that is sometimes brought up is that because of the short-circuiting nature of those operators, implementing them as methods is impossible or at least hard. I just wanted to see how hard it really is!
All the operators become methods. The logic is achieved through
polymorphism: basically, NilClass and FalseClass get one
set of implementations, Object gets the opposite set.
Lazy Evaluation is achieved with blocks: if a block is not
supposed to be evaluated, it is simply never yielded to.
At GitHub, of course!
gem install b001e
require 'b001e'
true.and { nil.or { 42 } }.if { puts "It's true!" }
# Equivalent to: if true && (nil || 42) then puts "It's true!" end
false.ifelse ->{ puts "You'll never see this." }, ->{ puts 'But this!' }
# Equivalent to: if false then puts "You'll never see this." else puts 'But this!' end
The API style is heavily influenced by Smalltalk.
The implementation is literally textbook: every introductory CS text should have it.
The Specs were directly lifted from the RubySpec project.
My original work is licensed under the MIT X11 License.
The RubySpec license is also MIT X11.