[DOC] String slices doc (#14740)

Author: BurdetteLamar

doc/string.rb

@@ -159,146 +159,6 @@
 # - #rstrip, #rstrip!: Strip trailing whitespace.
 # - #strip, #strip!: Strip leading and trailing whitespace.
 #
-# == +String+ Slices
-#
-# A _slice_ of a string is a substring selected by certain criteria.
-#
-# These instance methods utilize slicing:
-#
-# - String#[] (aliased as String#slice): Returns a slice copied from +self+.
-# - String#[]=: Mutates +self+ with the slice replaced.
-# - String#slice!: Mutates +self+ with the slice removed and returns the removed slice.
-#
-# Each of the above methods takes arguments that determine the slice
-# to be copied or replaced.
-#
-# The arguments have several forms.
-# For a string +string+, the forms are:
-#
-# - <tt>string[index]</tt>
-# - <tt>string[start, length]</tt>
-# - <tt>string[range]</tt>
-# - <tt>string[regexp, capture = 0]</tt>
-# - <tt>string[substring]</tt>
-#
-# <b><tt>string[index]</tt></b>
-#
-# When a non-negative integer argument +index+ is given,
-# the slice is the 1-character substring found in +self+ at character offset +index+:
-#
-#   'bar'[0]      # => "b"
-#   'bar'[2]      # => "r"
-#   'bar'[20]     # => nil
-#   'тест'[2]     # => "с"
-#   'こんにちは'[4] # => "は"
-#
-# When a negative integer +index+ is given,
-# the slice begins at the offset given by counting backward from the end of +self+:
-#
-#   'bar'[-3]      # => "b"
-#   'bar'[-1]      # => "r"
-#   'bar'[-20]     # => nil
-#
-# <b><tt>string[start, length]</tt></b>
-#
-# When non-negative integer arguments +start+ and +length+ are given,
-# the slice begins at character offset +start+, if it exists,
-# and continues for +length+ characters, if available:
-#
-#   'foo'[0, 2]      # => "fo"
-#   'тест'[1, 2]     # => "ес"
-#   'こんにちは'[2, 2] # => "にち"
-#   # Zero length.
-#   'foo'[2, 0]      # => ""
-#   # Length not entirely available.
-#   'foo'[1, 200]    # => "oo"
-#   # Start out of range.
-#   'foo'[4, 2]      # => nil
-#
-# Special case: if +start+ equals the length of +self+,
-# the slice is a new empty string:
-#
-#   'foo'[3, 2]    # => ""
-#   'foo'[3, 200]  # => ""
-#
-# When a negative +start+ and non-negative +length+ are given,
-# the slice begins by counting backward from the end of +self+,
-# and continues for +length+ characters, if available:
-#
-#   'foo'[-2, 2]     # => "oo"
-#   'foo'[-2, 200]   # => "oo"
-#   # Start out of range.
-#   'foo'[-4, 2]     # => nil
-#
-# When a negative +length+ is given, there is no slice:
-#
-#   'foo'[1, -1]   # => nil
-#   'foo'[-2, -1]  # => nil
-#
-# <b><tt>string[range]</tt></b>
-#
-# When a Range argument +range+ is given,
-# it creates a substring of +string+ using the indices in +range+.
-# The slice is then determined as above:
-#
-#   'foo'[0..1]     # => "fo"
-#   'foo'[0, 2]     # => "fo"
-#
-#   'foo'[2...2]    # => ""
-#   'foo'[2, 0]     # => ""
-#
-#   'foo'[1..200]   # => "oo"
-#   'foo'[1, 200]   # => "oo"
-#
-#   'foo'[4..5]     # => nil
-#   'foo'[4, 2]     # => nil
-#
-#   'foo'[-4..-3]   # => nil
-#   'foo'[-4, 2]    # => nil
-#
-#   'foo'[3..4]     # => ""
-#   'foo'[3, 2]     # => ""
-#
-#   'foo'[-2..-1]   # => "oo"
-#   'foo'[-2, 2]    # => "oo"
-#
-#   'foo'[-2..197]  # => "oo"
-#   'foo'[-2, 200]  # => "oo"
-#
-# <b><tt>string[regexp, capture = 0]</tt></b>
-#
-# When the Regexp argument +regexp+ is given,
-# and the +capture+ argument is <tt>0</tt>,
-# the slice is the first matching substring found in +self+:
-#
-#   'foo'[/o/]                # => "o"
-#   'foo'[/x/]                # => nil
-#   s = 'hello there'
-#   s[/[aeiou](.)\1/]        # => "ell"
-#   s[/[aeiou](.)\1/, 0]     # => "ell"
-#
-# If the argument +capture+ is provided and not <tt>0</tt>,
-# it should be either a capture group index (integer)
-# or a capture group name (String or Symbol);
-# the slice is the specified capture
-# (see {Groups and Captures}[rdoc-ref:Regexp@Groups+and+Captures]):
-#
-#   s = 'hello there'
-#   s[/[aeiou](.)\1/, 1] # => "l"
-#   s[/(?<vowel>[aeiou])(?<non_vowel>[^aeiou])/, "non_vowel"] # => "l"
-#   s[/(?<vowel>[aeiou])(?<non_vowel>[^aeiou])/, :vowel]      # => "e"
-#
-# If an invalid capture group index is given, there is no slice.
-# If an invalid capture group name is given, +IndexError+ is raised.
-#
-# <b><tt>string[substring]</tt></b>
-#
-# When the single +String+ argument +substring+ is given,
-# it returns the substring from +self+ if found, otherwise +nil+:
-#
-#   'foo'['oo'] # => "oo"
-#   'foo'['xx'] # => nil
-#
 # == What's Here
 #
 # First, what's elsewhere. Class +String+:

doc/string/aref.rdoc

@@ -0,0 +1,98 @@
+Returns the substring of +self+ specified by the arguments.
+
+<b>Form <tt>self[index]</tt></b>
+
+With non-negative integer argument +index+ given,
+returns the 1-character substring found in self at character offset index:
+
+  'hello'[0]    # => "h"
+  'hello'[4]    # => "o"
+  'hello'[5]    # => nil
+  'тест'[2]     # => "с"
+  'こんにちは'[4] # => "は"
+
+With negative integer argument +index+ given,
+counts backward from the end of +self+:
+
+  'hello'[-1] # => "o"
+  'hello'[-5] # => "h"
+  'hello'[-6] # => nil
+
+<b>Form <tt>self[start, length]</tt></b>
+
+With integer arguments +start+ and +length+ given,
+returns a substring of size +length+ characters (as available)
+beginning at character offset specified by +start+.
+
+If argument +start+ is non-negative,
+the offset is +start+:
+
+  'hello'[0, 1]  # => "h"
+  'hello'[0, 5]  # => "hello"
+  'hello'[0, 6]  # => "hello"
+  'hello'[2, 3]  # => "llo"
+  'hello'[2, 0]  # => ""
+  'hello'[2, -1] # => nil
+
+If argument +start+ is negative,
+counts backward from the end of +self+:
+
+  'hello'[-1, 1] # => "o"
+  'hello'[-5, 5] # => "hello"
+  'hello'[-1, 0] # => ""
+  'hello'[-6, 5] # => nil
+
+Special case: if +start+ equals the length of +self+,
+returns a new empty string:
+
+  'hello'[5, 3]  # => ""
+
+<b>Form <tt>self[range]</tt></b>
+
+With Range argument +range+ given,
+forms substring <tt>self[range.start, range.size]</tt>:
+
+  'hello'[0..2]  # => "hel"
+  'hello'[0, 3]  # => "hel"
+
+  'hello'[0...2] # => "he"
+  'hello'[0, 2]  # => "he"
+
+  'hello'[0, 0]  # => ""
+  'hello'[0...0] # => ""
+
+<b>Form <tt>self[regexp, capture = 0]</tt></b>
+
+With Regexp argument +regexp+ given and +capture+ as zero,
+searches for a matching substring in +self+;
+updates {Regexp-related global variables}[rdoc-ref:Regexp@Global+Variables]:
+
+  'hello'[/ell/]     # => "ell"
+  'hello'[/l+/]      # => "ll"
+  'hello'[//]        # => ""
+  'hello'[/nosuch/]  # => nil
+
+With +capture+ as a positive integer +n+,
+returns the +n+th matched group:
+
+  'hello'[/(h)(e)(l+)(o)/]    # => "hello"
+  'hello'[/(h)(e)(l+)(o)/, 1] # => "h"
+  $1                          # => "h"
+  'hello'[/(h)(e)(l+)(o)/, 2] # => "e"
+  $2                          # => "e"
+  'hello'[/(h)(e)(l+)(o)/, 3] # => "ll"
+  'hello'[/(h)(e)(l+)(o)/, 4] # => "o"
+  'hello'[/(h)(e)(l+)(o)/, 5] # => nil
+
+<b>Form <tt>self[substring]</tt></b>
+
+With string argument +substring+ given,
+returns the matching substring of +self+, if found:
+
+  'hello'['ell']      # => "ell"
+  'hello'['']         # => ""
+  'hello'['nosuch']   # => nil
+  'тест'['ес']        # => "ес"
+  'こんにちは'['んにち'] # => "んにち"
+
+Related: see {Converting to New String}[rdoc-ref:String@Converting+to+New+String].