ruby-standard-library

# Ruby Standard Library

Master Ruby's rich standard library. Ruby comes with powerful built-in classes and modules that handle common programming tasks elegantly.

## Enumerable

The Enumerable module provides iteration methods for collections.

### Common Enumerable Methods

```ruby
numbers = [1, 2, 3, 4, 5]

# map/collect - Transform elements
numbers.map { |n| n * 2 }  # [2, 4, 6, 8, 10]
numbers.map(&:to_s)        # ["1", "2", "3", "4", "5"]

# select/filter - Keep elements matching condition
numbers.select { |n| n.even? }  # [2, 4]
numbers.filter(&:odd?)          # [1, 3, 5]

# reject - Remove elements matching condition
numbers.reject { |n| n.even? }  # [1, 3, 5]

# find/detect - First element matching condition
numbers.find { |n| n > 3 }  # 4

# find_all - All elements matching condition (alias for select)
numbers.find_all { |n| n > 2 }  # [3, 4, 5]

# reduce/inject - Accumulate values
numbers.reduce(0) { |sum, n| sum + n }  # 15
numbers.reduce(:+)  # 15
numbers.reduce(:*)  # 120

# each - Iterate over elements
numbers.each { |n| puts n }

# each_with_index - Iterate with index
numbers.each_with_index { |n, i| puts "#{i}: #{n}" }

# each_with_object - Iterate with mutable object
numbers.each_with_object({}) { |n, hash| hash[n] = n * 2 }

# any? - True if any element matches
numbers.any? { |n| n > 4 }  # true
numbers.any?(&:even?)       # true

# all? - True if all elements match
numbers.all? { |n| n > 0 }  # true
numbers.all?(&:even?)       # false

# none? - True if no elements match
numbers.none? { |n| n < 0 }  # true

# one? - True if exactly one element matches
numbers.one? { |n| n == 3 }  # true

# partition - Split into two arrays [matching, non-matching]
evens, odds = numbers.partition(&:even?)

# group_by - Group elements by key
numbers.group_by { |n| n % 2 == 0 ? :even : :odd }
# => {:odd=>[1, 3, 5], :even=>[2, 4]}

# chunk - Group consecutive elements
[1, 2, 2, 3, 3, 3, 4].chunk(&:itself).to_a
# => [[1, [1]], [2, [2, 2]], [3, [3, 3, 3]], [4, [4]]]

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