diff options
| -rw-r--r-- | ChangeLog | 5 | ||||
| -rw-r--r-- | numeric.c | 70 |
2 files changed, 74 insertions, 1 deletions
@@ -1,3 +1,8 @@ +Mon Oct 5 15:39:30 2015 Zachary Scott <zzak@ruby-lang.org> + + * numeric.c: [DOC] Overview for Numeric class by Joe Corcoran + This patch was created at ROSSConf Berlin 2015 [Bug #11555] + Mon Oct 5 15:34:56 2015 Nobuyoshi Nakada <nobu@ruby-lang.org> * proc.c (proc_new): link ep to calling block. @@ -4071,7 +4071,75 @@ fix_even_p(VALUE num) */ /* - * The top-level number class. + * Document-class: Numeric + * + * Numeric is the class from which all higher-level numeric classes should inherit. + * + * Numeric allows instantiation of heap-allocated objects. Other core numeric classes such as + * Integer are implemented as immediates, which means that each Integer is a single immutable + * object which is always passed by value. + * + * a = 1 + * puts 1.object_id == a.object_id #=> true + * + * There can only ever be one instance of the integer +1+, for example. Ruby ensures this + * by preventing instantiation and duplication. + * + * Integer.new(1) #=> NoMethodError: undefined method `new' for Integer:Class + * 1.dup #=> TypeError: can't dup Fixnum + * + * For this reason, Numeric should be used when defining other numeric classes. + * + * Classes which inherit from Numeric must implement +coerce+, which returns a two-member + * Array containing an object that has been coerced into an instance of the new class + * and +self+ (see #coerce). + * + * Inheriting classes should also implement arithmetic operator methods (<code>+</code>, + * <code>-</code>, <code>*</code> and <code>/</code>) and the <code><=></code> operator (see + * Comparable). These methods may rely on +coerce+ to ensure interoperability with + * instances of other numeric classes. + * + * class Tally < Numeric + * def initialize(string) + * @string = string + * end + * + * def to_s + * @string + * end + * + * def to_i + * @string.size + * end + * + * def coerce(other) + * [self.class.new('|' * other.to_i), self] + * end + * + * def <=>(other) + * to_i <=> other.to_i + * end + * + * def +(other) + * self.class.new('|' * (to_i + other.to_i)) + * end + * + * def -(other) + * self.class.new('|' * (to_i - other.to_i)) + * end + * + * def *(other) + * self.class.new('|' * (to_i * other.to_i)) + * end + * + * def /(other) + * self.class.new('|' * (to_i / other.to_i)) + * end + * end + * + * tally = Tally.new('||') + * puts tally * 2 #=> "||||" + * puts tally > 1 #=> true */ void Init_Numeric(void) |