Programming Ruby: The Pragmatic Programmer's Guide

# Programming Ruby ### The Pragmatic Programmer's Guide
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class Range |
Parent: | Object
Version: | 1.6

### Index:

new === begin each end exclude_end? first last length size

A `Range` represents an interval---a set of values with a start and an end. Ranges may be constructed using the s `..` e and s `...` e literals, or with `Range.new` . Ranges constructed using `..` run from the start to the end inclusively. Those created using `...` exclude the end value. When used as an iterator, ranges return each value in the sequence.

`(-1..-5).to_a` | » | `[]`
`(-5..-1).to_a` | » | `[-5, -4, -3, -2, -1]`
`('a'..'e').to_a` | » | `["a", "b", "c", "d", "e"]`
`('a'...'e').to_a` | » | `["a", "b", "c", "d"]`

Ranges can be constructed using objects of any type, as long as the objects can be compared using their `<=>` operator and they support the `succ` method to return the next object in sequence.

`class Xs # represent a string of 'x's`
`include Comparable`
`attr :length`
`def initialize(n)`
`@length = n`
`end`
`def succ`
`Xs.new(@length + 1)`
`end`
`def <=>(other)`
`raise TypeError unless other.kind_of? Xs`
`@length <=> other.length`
`end`
`def inspect`
`'x' * @length`
`end`
`end`
``
`r = Xs.new(3)..Xs.new(6)` | » | `xxx..xxxxxx`
`r.to_a` | » | `[xxx, xxxx, xxxxx, xxxxxx]`
`r.member?(Xs.new(5))` | » | `true`

mixins
Enumerable: | collect, detect, each_with_index, entries, find, find_all, grep, include?, map, max, member?, min, reject, select, sort, to_a

class methods
new | Range.new( start, end, exclusive `=false` ) -> aRange
|  | Constructs a range using the given start and end. If the third parameter is omitted or is `false`, the range will include the end object; otherwise, it will be excluded.

instance methods
=== | rng === anObject -> `true` or `false`
|  | Returns `true` if anObject is an element of rng, `false` otherwise. Conveniently, `===` is the comparison operator used by `case` statements.
    case 79
    when 1..50   then   print "low\n"
    when 51..75  then   print "medium\n"
    when 76..100 then   print "high\n"
    end
produces:
    high
begin | rng.begin -> anObject
|  | Returns the first object of rng.
each | rng.each {| i | block } -> rng
|  | Iterates over the elements rng, passing each in turn to the block.
    (10..15).each do |n|
       print n, ' '
    end
produces:
    10 11 12 13 14 15
end | rng.end -> anObject
|  | Returns the object that defines the end of rng. See also `Range#length` .
`(1..10).end` | » | `10`
`(1...10).end` | » | `10`
exclude_end? | rng.exclude_end? -> `true` or `false`
|  | Returns `true` if rng excludes its end value.
first | rng.first -> anObject
|  | Returns the first object in rng.
last | rng.last -> anObject
|  | Synonym for `Range#end` .
length | rng.length -> anInteger
|  | Returns the number of objects in rng.
`(1..10).length` | » | `10`
`(1...10).length` | » | `9`
size | rng.size -> anInteger
|  | Synonym for `Range#length` .

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Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide"
Copyright © 2001 by Addison Wesley Longman, Inc. This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at http://www.opencontent.org/openpub/)).

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