From: Bernard Lambeau <blambeau@...>
Date: 2011-07-28T22:00:57+09:00
Subject: [ANN] myrrha 1.1.0 Released

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myrrha version 1.1.0 has been released!

Myrrha provides the coercion framework which is missing to Ruby, IMHO.

* <http://github.com/blambeau/myrrha>
* <http://rubydoc.info/gems/myrrha>
* <http://rubygems.org/gems/myrrha>

Myrrha provides the coercion framework which is missing to Ruby.
Coercions are
simply defined as a set of rules for converting values from source to
target domains
(in an abstract sense). As a typical and useful example, it comes
bundled with a
coerce() method providing a unique entry point for converting a string to a
numeric,
a boolean, a date, a time, an URI, and so on.

Changes:

# 1.1.0 / 2011-07-28

## Enhancements to coerce()

* Added coercion rules from Symbol/String to Module/Class

      coerce("Integer", Class)          # => Integer
      coerce(:Integer, Class)           # => Integer
      coerce("Myrrha::Version", Module) # => Myrrha::Version
      [... and so on ...]

* Added following coercion rules for Booleans

      coerce("true", TrueClass)         # => true
      coerce("false", FalseClass)       # => false

* Added coercion rule from any Object to String through ruby String(). Note
  that even with this coercion rule, coerce(nil, String) returns nil as
that
  rule has higher priority.

* require('time') is automatically issued when trying to coerce a String to
  a Time. Time.parse is obviously needed.

* Myrrha::Boolean (Boolean with core extensions) is now a sbyc domain (see
  below). Therefore, it is now a Class instance.

## Enhancements to the general coercion mechanism

* An optimistic coercion is tried when a rule is encountered whose target
  domain is a super domain of the requested one. Coercion only succeeds if
  the coerced value correctly belongs to the latter domain. Example:

      rules = Myrrha.coercions do |r|
        r.coercion String, Numeric, lambda{|s,t| Integer(s)}
      end
      rules.coerce("12", Integer) # => 12 in 1.1.0 while it failed in 1.0.0
      rules.coerce("12", Float)   # => Myrrha::Error

* You can now specify a coercion path, through an array of domains. For
  example (completely contrived, of course):

      rules = Myrrha.coercions do |r|
        r.coercion String,  Symbol, lambda{|s,t| s.to_sym }
        r.coercion Float,   String, lambda{|s,t| s.to_s   }
        r.coercion Integer, Float,  lambda{|s,t| Float(s) }
        r.coercion Integer, Symbol, [Float, String]
      end
      rules.coerce(12, Symbol)      # => :"12.0" as
Symbol(String(Float(12)))

* You can now define domains through specialization by constraint (sbyc) on
ruby
  classes, using Myrrha.domain:

      # Create a positive integer domain, as ... positive integers
      PosInt = Myrrha.domain(Integer){|i| i > 0 }

  Created domain is a real Class instance, that correctly responds to :===
  and :superclass. The feature is mainly introduced for supporting the
following
  kind of coercion scenarios (see README for more about this):

      rules = Myrrha.coercions do |r|
        r.coercion String, Integer, lambda{|s,t| Integer(s)}
      end
      rules.coerce("12",  PosInt) # => 12
      rules.coerce("-12", PosInt) # => ArgumentError, "Invalid value -12 for
PosInt"

## Bug fixes

* Fixed Coercions#dup when a set of rules has a main target domain. This
fixes
  the duplication of ToRubyLiteral rules, among others.

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