Merge pull request #4517 from Alex-Golub/master

[yaml/en] Add more information/examples about YAML capabilities

yaml.html.markdown

@@ -2,8 +2,10 @@
 language: yaml
 filename: learnyaml.yaml
 contributors:
+
 - [Leigh Brenecki, 'https://leigh.net.au']
 - [Suhas SG, 'https://github.com/jargnar']
+
 ---
 
 YAML is a data serialisation language designed to be directly writable and
@@ -17,6 +19,7 @@ YAML doesn't allow literal tab characters for indentation.
 ---  # document start
 
 # Comments in YAML look like this.
+# YAML support single-line comments.
 
 ################
 # SCALAR TYPES #
@@ -28,11 +31,23 @@ key: value
 another_key: Another value goes here.
 a_number_value: 100
 scientific_notation: 1e+12
-# The number 1 will be interpreted as a number, not a boolean. if you want
-# it to be interpreted as a boolean, use true
+hex_notation: 0x123  # evaluates to 291
+octal_notation: 0123 # evaluates to 83
+
+# The number 1 will be interpreted as a number, not a boolean. 
+# If you want it to be interpreted as a boolean, use true.
 boolean: true
 null_value: null
 key with spaces: value
+
+# Yes and No (doesn't matter the case) will be evaluated to boolean 
+# true and false values respectively.
+# To use the actual value use single or double quotes.
+no: no            # evaluates to "false": false
+yes: No           # evaluates to "true": false
+not_enclosed: yes # evaluates to "not_enclosed": true
+enclosed: "yes"   # evaluates to "enclosed": yes
+
 # Notice that strings don't need to be quoted. However, they can be.
 however: 'A string, enclosed in quotes.'
 'Keys can be quoted too.': "Useful if you want to put a ':' in your key."
@@ -41,25 +56,49 @@ double quotes: "have many: \", \0, \t, \u263A, \x0d\x0a == \r\n, and more."
 # UTF-8/16/32 characters need to be encoded
 Superscript two: \u00B2
 
-# Multiple-line strings can be written either as a 'literal block' (using |),
+# Special characters must be enclosed in single or double quotes
+special_characters: "[ John ] & { Jane } - <Doe>"
+
+# Multiple-line strings can be written either as a 'literal block' (using |), 
 # or a 'folded block' (using '>').
+# Literal block turn every newline within the string into a literal newline (\n).
+# Folded block removes newlines within the string.
 literal_block: |
-    This entire block of text will be the value of the 'literal_block' key,
-    with line breaks being preserved.
+  This entire block of text will be the value of the 'literal_block' key,
+  with line breaks being preserved.
 
-    The literal continues until de-dented, and the leading indentation is
-    stripped.
+  The literal continues until de-dented, and the leading indentation is
+  stripped.
 
-        Any lines that are 'more-indented' keep the rest of their indentation -
-        these lines will be indented by 4 spaces.
+      Any lines that are 'more-indented' keep the rest of their indentation -
+      these lines will be indented by 4 spaces.
 folded_style: >
-    This entire block of text will be the value of 'folded_style', but this
-    time, all newlines will be replaced with a single space.
+  This entire block of text will be the value of 'folded_style', but this
+  time, all newlines will be replaced with a single space.
 
-    Blank lines, like above, are converted to a newline character.
+  Blank lines, like above, are converted to a newline character.
 
-        'More-indented' lines keep their newlines, too -
-        this text will appear over two lines.
+      'More-indented' lines keep their newlines, too -
+      this text will appear over two lines.
+
+# |- and >- removes the trailing blank lines (also called literal/block "strip")
+literal_strip: |-
+  This entire block of text will be the value of the 'literal_block' key,
+  with trailing blank line being stripped.
+block_strip: >-
+  This entire block of text will be the value of 'folded_style', but this
+  time, all newlines will be replaced with a single space and 
+  trailing blank line being stripped.
+
+# |+ and >+ keeps trailing blank lines (also called literal/block "keep")
+literal_keep: |+
+  This entire block of text will be the value of the 'literal_block' key,
+  with trailing blank line being kept.
+
+block_keep: >+
+  This entire block of text will be the value of 'folded_style', but this
+  time, all newlines will be replaced with a single space and 
+  trailing blank line being kept.
 
 ####################
 # COLLECTION TYPES #
@@ -87,7 +126,7 @@ a_nested_map:
 # An example
 ? - Manchester United
   - Real Madrid
-: [2001-01-01, 2002-02-02]
+: [ 2001-01-01, 2002-02-02 ]
 
 # Sequences (equivalent to lists or arrays) look like this
 # (note that the '-' counts as indentation):
@@ -98,24 +137,26 @@ a_sequence:
   - Item 4
   - key: value
     another_key: another_value
-  -
-    - This is a sequence
+  - - This is a sequence
     - inside another sequence
   - - - Nested sequence indicators
       - can be collapsed
 
 # Since YAML is a superset of JSON, you can also write JSON-style maps and
 # sequences:
-json_map: {"key": "value"}
-json_seq: [3, 2, 1, "takeoff"]
-and quotes are optional: {key: [3, 2, 1, takeoff]}
+json_map: { "key": "value" }
+json_seq: [ 3, 2, 1, "takeoff" ]
+and quotes are optional: { key: [ 3, 2, 1, takeoff ] }
 
 #######################
 # EXTRA YAML FEATURES #
 #######################
 
 # YAML also has a handy feature called 'anchors', which let you easily duplicate
-# content across your document. Both of these keys will have the same value:
+# content across your document.
+# Anchors identified by & character which define the value.
+# Aliases identified by * character which acts as "see above" command.
+# Both of these keys will have the same value:
 anchored_content: &anchor_name This string will appear as the value of two keys.
 other_anchor: *anchor_name
 
@@ -123,28 +164,35 @@ other_anchor: *anchor_name
 base: &base
   name: Everyone has same name
 
-# The regexp << is called Merge Key Language-Independent Type. It is used to
+# The regexp << is called 'Merge Key Language-Independent Type'. It is used to
 # indicate that all the keys of one or more specified maps should be inserted
 # into the current map.
-
+# NOTE: If key already exists alias will not be merged
 foo:
-  <<: *base
+  <<: *base # doesn't merge the anchor
   age: 10
-
+  name: John
 bar:
-  <<: *base
+  <<: *base # base anchor will be merged
   age: 20
 
 # foo and bar would also have name: Everyone has same name
 
 # YAML also has tags, which you can use to explicitly declare types.
+# Syntax: !![typeName] [value]
+explicit_boolean: !!bool true
+explicit_integer: !!int 42
+explicit_float: !!float -42.24
 explicit_string: !!str 0.5
+explicit_datetime: !!timestamp 2022-11-17 12:34:56.78 +9
+explicit_null: !!null null
+
 # Some parsers implement language specific tags, like this one for Python's
 # complex number type.
 python_complex_number: !!python/complex 1+2j
 
 # We can also use yaml complex keys with language specific tags
-? !!python/tuple [5, 7]
+? !!python/tuple [ 5, 7 ]
 : Fifty Seven
 # Would be {(5, 7): 'Fifty Seven'} in Python
 
@@ -154,9 +202,10 @@ python_complex_number: !!python/complex 1+2j
 
 # Strings and numbers aren't the only scalars that YAML can understand.
 # ISO-formatted date and datetime literals are also parsed.
-datetime: 2001-12-15T02:59:43.1Z
-datetime_with_spaces: 2001-12-14 21:59:43.10 -5
-date: 2002-12-14
+datetime_canonical: 2001-12-15T02:59:43.1Z
+datetime_space_seperated_with_time_zone: 2001-12-14 21:59:43.10 -5
+date_implicit: 2002-12-14
+date_explicit: !!timestamp 2002-12-14
 
 # The !!binary tag indicates that a string is actually a base64-encoded
 # representation of a binary blob.
@@ -171,7 +220,7 @@ set:
   ? item1
   ? item2
   ? item3
-or: {item1, item2, item3}
+or: { item1, item2, item3 }
 
 # Sets are just maps with null values; the above is equivalent to:
 set2:
@@ -186,3 +235,4 @@ set2:
 
 + [YAML official website](https://yaml.org/)
 + [Online YAML Validator](http://www.yamllint.com/)
++ [JSON ⇆ YAML](https://www.json2yaml.com/)